Knucklehead Tire Change - How to Video
The first step is to make sure that you really need a new tire. Humor.
(finally gave up on trying to upload this, and put it on You Tube instead)
Showing posts with label Knucklehead Tech. Show all posts
Showing posts with label Knucklehead Tech. Show all posts
When we left off in part one, we had looked at and discussed four of the five issues relating to running Knuckle heads of a Shovelhead Cone lower end. We talked about rocker arm ratios, lifter blocks, cams and pushrod tube angles. That leaves the toughest issue for last; oil return from the top end.
Perhaps a review of how the stock Knuckle oil return system works is in order. Starting on one end of the system, the Knuckle breather gear has a hole that is not found in any later breathers. This hole is timed to provide crankcase vacuum to a passage (also unique to Knuckle cases) which connects to the Knuckle lifter blocks. That is what the fifth hole in a Knuckle lifter block gasket is for. In this way, crankcase vacuum is applied to the pushrod tubes and the aluminum housings which give the Knucklehead its name.
Note that this passage in the Knuckle lifter block goes to the top of the lifter, with no drain hole into the gearcase such as on a Pan or Shovel. In fact, if you have replaced your Knuckle lifters with any aftermarket lifter (with the exception of the ones from S&S, which are made correctly) there is a good chance that you have a hole drilled through the lifter which will bleed off the vacuum that is needed to evacuate the heads. This hole is not supposed to be there, and could very well be the root cause of your smoking and oil consumption on your stock Knuck.
The reason that this vacuum in the pushrod tubes and Knuckle housing is critical, is that the 'spring cups" depend on that vacuum to "suck" the oil, through the 3/16" O.D. Steel lines uphill into the housings. If you have ever had a Knuckle head apart, you are no doubt familiar with the seals that are between the aluminum housing and the tin covers. These not only seal the assembly from leaking to the outside, but they also separate the two sides of the rocker arm to keep vacuum on one side only.
Compare this to the oil return on a Shovel, Pan, or Evo. All of them return the oil from the heads via a passage through the cylinder directly to the crankcase. They basically depend on gravity aided by crankcase vacuum when the pistons are on the upstroke (or crankcase vacuum aided by gravity, if you prefer).
So, what are you to do, if you have a set of Knuckle heads, and a Cone lower end you are dying to put them on? It looks as though there are a few possibilities. One which I have performed is to rework the steel lines coming out of the spring cups so that they don't run uphill as much as in the stock application. From there grafting on soft lines and routing them externally down to the crankcase roughly adjacent to the timing plug converts the drainage from the spring cups into the gravity/crankcase vacuum style like Pans and Shovels. The oil from the aluminum "knuckle" returns down the pushrod tubes.
A second method comes directly from a comment received on what I posted in part one of "Cone Knuckle." Richard writes that he has been running a Knuckle-Cone motor since 1986. He uses Shovel lifter blocks with a brake tube brazed to the intake pushrod tube and plumbs this into the fitting on the crankcase that returns oil from the primary in stock configuration. This puts timed vacuum to the heads much like the stock system and so avoids any mods to the spring cups, etc. I think this is an absolutely brilliant idea, and though I had considered the idea of using the primary return, my thought was to go directly from the spring cups to the primary return. Richard's system is much simpler and cleaner! Thank you Richard!
But, now there is one more viable option. It turns out that I have a reader who works for S&S Cycle. After reading part one, he informed me, and got permission for me to break the news, that S&S is introducing a complete Cone Knuckle engine this summer. The S&S version will be called the Kone Knuckle, and will feature appropriate passages and machining to use Knuckle lifter blocks, and hence a stock style oil return system. Plans are to also make the cases available for those of you who have a bunch of Knuck parts stashed away for just such a project. This will make the whole process relatively painless.
Keep in mind though, that excess clearance between the Knuckle rocker arms and shafts can be a source of excessive oil in the top end, enough that even an otherwise correctly working return system will not keep up with. A rebuild of those parts may still be in order.
So, just one last thought. Whoever said that Cone Knuckleheads couldn't/shouldn't be built ....well, aren't you glad that neither Richard or S&S listened to them.
Perhaps a review of how the stock Knuckle oil return system works is in order. Starting on one end of the system, the Knuckle breather gear has a hole that is not found in any later breathers. This hole is timed to provide crankcase vacuum to a passage (also unique to Knuckle cases) which connects to the Knuckle lifter blocks. That is what the fifth hole in a Knuckle lifter block gasket is for. In this way, crankcase vacuum is applied to the pushrod tubes and the aluminum housings which give the Knucklehead its name.
Note that this passage in the Knuckle lifter block goes to the top of the lifter, with no drain hole into the gearcase such as on a Pan or Shovel. In fact, if you have replaced your Knuckle lifters with any aftermarket lifter (with the exception of the ones from S&S, which are made correctly) there is a good chance that you have a hole drilled through the lifter which will bleed off the vacuum that is needed to evacuate the heads. This hole is not supposed to be there, and could very well be the root cause of your smoking and oil consumption on your stock Knuck.
The reason that this vacuum in the pushrod tubes and Knuckle housing is critical, is that the 'spring cups" depend on that vacuum to "suck" the oil, through the 3/16" O.D. Steel lines uphill into the housings. If you have ever had a Knuckle head apart, you are no doubt familiar with the seals that are between the aluminum housing and the tin covers. These not only seal the assembly from leaking to the outside, but they also separate the two sides of the rocker arm to keep vacuum on one side only.
Compare this to the oil return on a Shovel, Pan, or Evo. All of them return the oil from the heads via a passage through the cylinder directly to the crankcase. They basically depend on gravity aided by crankcase vacuum when the pistons are on the upstroke (or crankcase vacuum aided by gravity, if you prefer).
So, what are you to do, if you have a set of Knuckle heads, and a Cone lower end you are dying to put them on? It looks as though there are a few possibilities. One which I have performed is to rework the steel lines coming out of the spring cups so that they don't run uphill as much as in the stock application. From there grafting on soft lines and routing them externally down to the crankcase roughly adjacent to the timing plug converts the drainage from the spring cups into the gravity/crankcase vacuum style like Pans and Shovels. The oil from the aluminum "knuckle" returns down the pushrod tubes.
A second method comes directly from a comment received on what I posted in part one of "Cone Knuckle." Richard writes that he has been running a Knuckle-Cone motor since 1986. He uses Shovel lifter blocks with a brake tube brazed to the intake pushrod tube and plumbs this into the fitting on the crankcase that returns oil from the primary in stock configuration. This puts timed vacuum to the heads much like the stock system and so avoids any mods to the spring cups, etc. I think this is an absolutely brilliant idea, and though I had considered the idea of using the primary return, my thought was to go directly from the spring cups to the primary return. Richard's system is much simpler and cleaner! Thank you Richard!
But, now there is one more viable option. It turns out that I have a reader who works for S&S Cycle. After reading part one, he informed me, and got permission for me to break the news, that S&S is introducing a complete Cone Knuckle engine this summer. The S&S version will be called the Kone Knuckle, and will feature appropriate passages and machining to use Knuckle lifter blocks, and hence a stock style oil return system. Plans are to also make the cases available for those of you who have a bunch of Knuck parts stashed away for just such a project. This will make the whole process relatively painless.
Keep in mind though, that excess clearance between the Knuckle rocker arms and shafts can be a source of excessive oil in the top end, enough that even an otherwise correctly working return system will not keep up with. A rebuild of those parts may still be in order.
So, just one last thought. Whoever said that Cone Knuckleheads couldn't/shouldn't be built ....well, aren't you glad that neither Richard or S&S listened to them.
Knuckle heads on a cone style Shovel bottom end. Most have seen one, so there is not much debate as to whether it can be done, but there is much disagreement as to whether it should ever be done. Those who say it shouldn't be done generally fall into one of two camps. The purist, who believes that it is sacrilege to desecrate a set of Knuckle heads by running them on anything but a set of Knuckle cases, and the quasi engineers who see nothing but disaster when a part does not work exactly as the designer envisioned.
On the other side of the issue are two likewise divergent camps. On the one hand you have the less-than-a-shade-tree mechanic who will throw together nearly any combination of parts that will physically fit together and leave the "making it work" for the next owner. On the other is the wrench who does his best to weigh the issues and address them in such a way that the finished product is functional as well as unique.
Having raced a Knuckle top/ Cone bottom drag bike for a number of years, I can attest to the fact that those who say that there are too many cam/rocker arm/geometry problems for a motor like that to run well are wrong. Two AMRA National Championships would suggest that they are very wrong. In fact, performance is easily addressed by standard methods. Making the motor streetable in regards to the oiling system is a much more difficult proposition.
There are a number of things to consider before building a Cone Knuckle. In no particular order, they are:
1. Different rocker arm ratio. Knuckle rockers are 1:1. Shovel rockers are 1.43:1. That means that a cam that lifts the valve .450 in a Shovel will lift it .315 in a Knuck. (.450 divided by 1.43)
2. Knuckle lifter blocks don't bolt onto Cone cases. Some of the bolt holes are close, but no cigar, and there is no oil port in the case to match the one in the Knuckle lifter blocks.
3. A Knuckle cam will not fit in a Cone cam cover (at least without major modifications).
4. The angle of the pushrod tubes is different between a Knuckle and a Shovel or Pan making it difficult to seal the bottom of the pushrod tube to a Shovel/Pan lifter block.
5. The oil return system from the heads is completely different between a Knuckle and a Shovel, Pan, or Evo.
Looking at the rocker arm ratios first, there are a number of ways to approach this. One is to have a cam custom ground with Knuckle profile lobes for use with Shovel lifter blocks. This solves any and all valve timing and lift discrepancies, but will be expensive and time consuming.
The second method would be to select a high lift Shovelhead cam. Stock and mild performance Knuckle cams are from .350 to .370" lift. Taking into account the Shovelhead rocker ratio of 1.43:1, you can see that a Shovel cam that is advertised as .500 to .530 lift will open the valve .350 to .370 in a Knuck. If you consider the S&S 514 Shovelhead cam, its .514 lift translates to .359' lift with the Knuck's 1:1 rocker ratio. Compare its other specs with two Andrews Knuckle cams; the N is considered a stock replacement and the S a performance cam.
S&S 514 - IO 23/IC 43 (246 duration) and EO 43/EC 23 (246 duration)
Andrews N - IO 13/IC 41 (234 duration) and EO 44/EC 16 (240 duration)
Andrews S - IO 27/IC 55 (262 duration) and EO 55/EC 27 (262 duration)
As you can see, the S&S 514 falls nicely between the specs of a stock and a performance Knuck cam. Seems like a no brainer to me that this (or a similar cam grind) would be a viable choice.
Using Knuckle lifter blocks on a Cone lower end, while possible, would require quite a bit of welding and machining as well as a custom ground cam (or even more machining to fit a Knuck cam to a Cone cam cover). Not really practical unless you are a machinist by trade and just want to show off.
If you have by now settled on using Shovel lifter blocks, the next issue is the angle at which the pushrod tube meets the block. Now back when I was racing, this was a non issue, since I ran no oil to the top end, and no pushrod tubes. This lack of pushrod tubes did, however leave me with a couple memories that will give a clue as to the solution to the problem of sealing them up. On my Cone Knuckle drag bike the pushrods appeared to be perfectly in line with the lifters. I mean straight as an arrow (at least to the naked eye).This was especially noticeable in comparison to the Shovel dragbikes which were its contemporarys. The pushrods on a Shovel were at a fairly drastic angle coming off the top of the lifters. One might never notice that if they have never looked at a Shovel motor with pushrods installed, but no covers. The reason is because the Knuckle has four different lengths of rocker arm so each one aligns with its corresponding lifter. Not so on a Shovel (or Pan, or Evo, or even Twin Cam). The misalignment on these "modern" motors is compensated for by the ball and socket arrangement on each end of the pushrod.
If you look at a Shovel lifter block, you will notice that the "seating surface" for the cork seal is NOT perpendicular to the bore for the lifter. Well, one of them is probably perpendicular, but the other three are canted to line the tube up with the rocker/box. I have not had a chance to try this, but I suspect that aligning the pushrod tubes on a Cone Knuck may be as simple as remachining the seating surface in the blocks so that they are perpendicular to the lifter bore.
Finally, we come to the oil return system from the heads. Oil return from the heads is the biggest obstacle in making the Cone Knuckle streetable. Since it is fairly involved, it will have to wait for another post - coming soon in part 2.
On the other side of the issue are two likewise divergent camps. On the one hand you have the less-than-a-shade-tree mechanic who will throw together nearly any combination of parts that will physically fit together and leave the "making it work" for the next owner. On the other is the wrench who does his best to weigh the issues and address them in such a way that the finished product is functional as well as unique.
Having raced a Knuckle top/ Cone bottom drag bike for a number of years, I can attest to the fact that those who say that there are too many cam/rocker arm/geometry problems for a motor like that to run well are wrong. Two AMRA National Championships would suggest that they are very wrong. In fact, performance is easily addressed by standard methods. Making the motor streetable in regards to the oiling system is a much more difficult proposition.
There are a number of things to consider before building a Cone Knuckle. In no particular order, they are:
1. Different rocker arm ratio. Knuckle rockers are 1:1. Shovel rockers are 1.43:1. That means that a cam that lifts the valve .450 in a Shovel will lift it .315 in a Knuck. (.450 divided by 1.43)
2. Knuckle lifter blocks don't bolt onto Cone cases. Some of the bolt holes are close, but no cigar, and there is no oil port in the case to match the one in the Knuckle lifter blocks.
3. A Knuckle cam will not fit in a Cone cam cover (at least without major modifications).
4. The angle of the pushrod tubes is different between a Knuckle and a Shovel or Pan making it difficult to seal the bottom of the pushrod tube to a Shovel/Pan lifter block.
5. The oil return system from the heads is completely different between a Knuckle and a Shovel, Pan, or Evo.
Looking at the rocker arm ratios first, there are a number of ways to approach this. One is to have a cam custom ground with Knuckle profile lobes for use with Shovel lifter blocks. This solves any and all valve timing and lift discrepancies, but will be expensive and time consuming.
The second method would be to select a high lift Shovelhead cam. Stock and mild performance Knuckle cams are from .350 to .370" lift. Taking into account the Shovelhead rocker ratio of 1.43:1, you can see that a Shovel cam that is advertised as .500 to .530 lift will open the valve .350 to .370 in a Knuck. If you consider the S&S 514 Shovelhead cam, its .514 lift translates to .359' lift with the Knuck's 1:1 rocker ratio. Compare its other specs with two Andrews Knuckle cams; the N is considered a stock replacement and the S a performance cam.
S&S 514 - IO 23/IC 43 (246 duration) and EO 43/EC 23 (246 duration)
Andrews N - IO 13/IC 41 (234 duration) and EO 44/EC 16 (240 duration)
Andrews S - IO 27/IC 55 (262 duration) and EO 55/EC 27 (262 duration)
As you can see, the S&S 514 falls nicely between the specs of a stock and a performance Knuck cam. Seems like a no brainer to me that this (or a similar cam grind) would be a viable choice.
Using Knuckle lifter blocks on a Cone lower end, while possible, would require quite a bit of welding and machining as well as a custom ground cam (or even more machining to fit a Knuck cam to a Cone cam cover). Not really practical unless you are a machinist by trade and just want to show off.
If you have by now settled on using Shovel lifter blocks, the next issue is the angle at which the pushrod tube meets the block. Now back when I was racing, this was a non issue, since I ran no oil to the top end, and no pushrod tubes. This lack of pushrod tubes did, however leave me with a couple memories that will give a clue as to the solution to the problem of sealing them up. On my Cone Knuckle drag bike the pushrods appeared to be perfectly in line with the lifters. I mean straight as an arrow (at least to the naked eye).This was especially noticeable in comparison to the Shovel dragbikes which were its contemporarys. The pushrods on a Shovel were at a fairly drastic angle coming off the top of the lifters. One might never notice that if they have never looked at a Shovel motor with pushrods installed, but no covers. The reason is because the Knuckle has four different lengths of rocker arm so each one aligns with its corresponding lifter. Not so on a Shovel (or Pan, or Evo, or even Twin Cam). The misalignment on these "modern" motors is compensated for by the ball and socket arrangement on each end of the pushrod.
If you look at a Shovel lifter block, you will notice that the "seating surface" for the cork seal is NOT perpendicular to the bore for the lifter. Well, one of them is probably perpendicular, but the other three are canted to line the tube up with the rocker/box. I have not had a chance to try this, but I suspect that aligning the pushrod tubes on a Cone Knuck may be as simple as remachining the seating surface in the blocks so that they are perpendicular to the lifter bore.
Finally, we come to the oil return system from the heads. Oil return from the heads is the biggest obstacle in making the Cone Knuckle streetable. Since it is fairly involved, it will have to wait for another post - coming soon in part 2.
I intended to post something entirely different, but at the moment, Blogger is not letting me cut and paste, so rather than rewriting something I have saved in another program, I will do something fresh.
Some time ago I started a series on installing bigger intake valves in a Knuckle head. This will be the second part of that series. When I left off, I had finished installing new exhaust seats. The seats from Rowe machine nicely (something that cannot be said for the 60+ year work hardened original seats. This also allows you to set the stem protrusion of the new valves, avoiding mis-matched depths.
If the intake nipples were removed for replacement (and in most cases they should be), now is the time to re-install them. I like to use JB Weld on the threads of the nipples, along with a stock type rivet. The epoxy is particularly important when porting, since some of the inner threads inevitably will be ground away. Here's a tip: from here on out, keep a set of used intake nuts screwed on to the nipples to protect those nice new threads.
Now that the new seats and intake nipples are installed, it is time for porting work, if you plan to do so. Doing this before new guides are installed allows you to do the best possible job. Disregarding the area just below the seat and the short side radius, the remainder of both ports should be shaped and finished as per the final product. I like a 50 grit on the intake, and a polished exhaust. However if the exhaust port is to get a thermal barrier coating, there is no point in spending extra time doing a fine polish.
With the majority of the porting work done, it is time to paint the heads. This needs to happen before guide installation, since the spring cups are held in by the valve guides. For a stock look, I use a semi-gloss black, and bake it on at about 200 degrees. Many of the hi temp paints available need this heat cycle to enable them to stand up to standard parts wash fluid. Nothing worse than keeping the new paint looking good through the whole process, only to have it get sticky and wipe off during the final wash prior to final assembly.
While the paint is drying on the heads, it is a good time to make sure the spring cups are ready to go. Often you will find a small crack just below the return tube. Be sure to weld these before going any further. Next, all of the gasket surfaces on the cups should be attended to. I use several purpose built forms along with a small hammer to return them to their original shapes. Don't forget to re-flatten the bottom portion that the guide will seal against. Once the cups are all in shape, they can be Parkerized if you are going for a stock look.
Guide installation, cutting the seats, and final porting work will be covered in the next installment.
Some time ago I started a series on installing bigger intake valves in a Knuckle head. This will be the second part of that series. When I left off, I had finished installing new exhaust seats. The seats from Rowe machine nicely (something that cannot be said for the 60+ year work hardened original seats. This also allows you to set the stem protrusion of the new valves, avoiding mis-matched depths.
If the intake nipples were removed for replacement (and in most cases they should be), now is the time to re-install them. I like to use JB Weld on the threads of the nipples, along with a stock type rivet. The epoxy is particularly important when porting, since some of the inner threads inevitably will be ground away. Here's a tip: from here on out, keep a set of used intake nuts screwed on to the nipples to protect those nice new threads.
Now that the new seats and intake nipples are installed, it is time for porting work, if you plan to do so. Doing this before new guides are installed allows you to do the best possible job. Disregarding the area just below the seat and the short side radius, the remainder of both ports should be shaped and finished as per the final product. I like a 50 grit on the intake, and a polished exhaust. However if the exhaust port is to get a thermal barrier coating, there is no point in spending extra time doing a fine polish.
With the majority of the porting work done, it is time to paint the heads. This needs to happen before guide installation, since the spring cups are held in by the valve guides. For a stock look, I use a semi-gloss black, and bake it on at about 200 degrees. Many of the hi temp paints available need this heat cycle to enable them to stand up to standard parts wash fluid. Nothing worse than keeping the new paint looking good through the whole process, only to have it get sticky and wipe off during the final wash prior to final assembly.
While the paint is drying on the heads, it is a good time to make sure the spring cups are ready to go. Often you will find a small crack just below the return tube. Be sure to weld these before going any further. Next, all of the gasket surfaces on the cups should be attended to. I use several purpose built forms along with a small hammer to return them to their original shapes. Don't forget to re-flatten the bottom portion that the guide will seal against. Once the cups are all in shape, they can be Parkerized if you are going for a stock look.
Guide installation, cutting the seats, and final porting work will be covered in the next installment.
I received a set of S&S/Flathead Power 74 inch Knuckle cylinders into the shop last week, and thought there may be an interest in some comparison shots. The black powder-coating on the S&S cylinder on the left is a little too glossy for my taste, but will doubtless hold up well.
A nice touch is the cast in emblem which suggests (but does not copy) the original's MC (Milwaukee Casting) badge
Even the pistons that come with the cylinders have a dome that is reminiscent of their vintage counterpart. On left is the new S&S cast 74" piston, on the right an English made replacement piston from back in the day.
Currently the S&S suggested retail for a set of these cylinders is $980 with pistons, or $850 for cylinders alone. Not cheap by any means, but certainly a worthwhile investment if you plan serious performance modifications.
As I mentioned previously, one of the items I would like to cover on my blog this year is installation of big intake valves in a set of Knuckle heads. If you are dealing with stock heads, it is quite likely that you will find good reason to give the exhaust seat inserts attention also. Sometimes the stock exhaust seat is simply sunk too deeply from multiple valve jobs. Often the seat will be pitted so badly as to be unusable. But even if those two items are not an issue, you may want to consider replacing them because they have become extremely "work hardened" from 60+ years of use. While this extreme hardness is not an issue while in service, it makes the seats very hard to work with. Modern seat cutting equipment will invariably chatter, and stone type seat grinders will require lots of time and constant dressing if there are any misalignment issues to be corrected.
So, as part one of this series on installing bigger intake valves in a Knuckle, we will look at replacing the exhaust seats, though if you are planning to use stock size intakes, the same procedure can be used for those seats.
ABOVE: Removing the old seat inserts is pretty simple on a Knuck. With the guide removed, a slim punch will fit though the guide hole and can be angled to catch the back side of the insert. A few taps and your heads should now look like this. (both intake and exhaust seats removed)
ABOVE: Once the seat recess has been cleaned, carefully measure the bore in multiple places to determine how much press fit the new insert will have. You want a minimum of .004" interference, though I prefer .005"-.006".
ABOVE: A home made tool will work for seat installation. This one is made using an old valve with a collar welded just below the face to keep the new insert centered, and a piece of scrap for a handle. Shown here with new insert not seated on collar.
ABOVE: Tool with new seat insert seated on collar. A "dummy" guide will have to be installed temporarily in head to keep everything aligned so that the seat goes in straight. You can always use your old guide (you didn't throw it away did you?), sanded down a bit so it is only about a half thousandth press in the head.
ABOVE: Prior to actual installation, put the head in your oven at 500 degrees (that is the head in your oven, not your head in the oven) and the seat insert in your freezer. If the head is clean, it should not stink up the kitchen, but if it isn't and your wife catches you, you may want to go back to putting your head in the oven. Unlike with an aluminum head, even with a heated head and frozen guide, you will have to use moderate blows with a hammer to install the seats.
ABOVE: Here is the head with new exhaust seat insert installed. Now you can remove the dummy guide and proceed with the valve job, which will be covered in a future post.
One last thing, if you are having trouble finding suitable valve seat inserts, you can follow the link at the bottom of the left hand column of this blog to my eBay store. I will generally have what you need in stock.
In my last post I featured a Leineweber # 5 Knuckle cam. This elicited a response from a reader, Jim Franco, saying that he has a cam that recently came out of a Knucklehead hillclimber with lobes that looked quite similar. He was kind enough to send me some pictures of the cam, which I have posted here. The holes in the drive gear immediately bring to mind the legendary Knucklehead "Lightning" cam. Contrary to what seems to be popular opinion, I do not believe that the Lightning cam was the only factory cam to have these holes.
As can be seen in the above picture, the lobes do have the radical shape similar to the Leineweber #5. I have heard the Lightning cam referred to as the "banana lobe cam." I am not sure if this was a common slang term for it or not, but one can certainly see where the name came from.
I ran a factory Knuckle cam which had holes like this in my street bike for a few seasons. The lobes did not visually appear any different from any other stock Knuck cam, and it did not perform noticeably better. I also do not remember a keyway, like the one seen in the above picture.
Barring someone with more knowledge of the elusive Knucklehead Lightning speaking up, I am very inclined to conclude that Jim has himself a genuine one here!
Thought you might enjoy seeing a somewhat rare cam. This is a Leineweber #5 Knucklehead cam. It is .540" lift with the Knuckle's 1:1 rocker arm ratio. The description for this cam is as follows: Radical racing cam. Designed for fuel, alcohol, or gasoline. Major engine modifications needed to fit this cam. Expert engine builder a must.
Is that cool or what? The lobes at 8 and 12 o'clock are the intakes, and the milder exhaust lobe is the one at 3 o'clock. Jim Leineweber only lists his Knuck cam specs at .020" lift. For this cam the duration is 318 degrees on the intake and 298 degrees for the exhaust. The picture doesn't do it justice as to just how radical this cam looks!
Twenty + years ago a local drag racer from the '60s and 70's, the late Doug Gall, showed me a cam which Jim Leineweber had ground for him. He told me it was one of Jim's first. It was a stock cam that had been welded up and reground. As I recall, it had much this same shape to the lobes.
The best part is you can still get one of these for your own nitro burning Knucklehead at leinewebercams.com (or contact me).
Here's one that is frankly on the verge of being a little embarrassing. When I bought my first Knucklehead nearly 30 years ago it had a set of Champion D14 plugs in it. For about the next 20+ years, whenever I replaced plug on any of my Knuckles I would simply go to my local Napa and buy another set of D14s.
Then somewhere along the line, I became aware that the Champion D16 was the correct cross reference for the Knuckle. So, after all those years I was faced with no longer being able to remember which number was right and which was the one I had used for so many years. Have I mentioned lately that its no picnic getting old?
So for the last couple of years, every time I have been asked for a spark plug for a Knuckle, I have not been able to remember which was correct; D14 or D16. That all changed the other day when I was researching something else. I happened to run across this in Palmer's "How to Restore Your Harley Davidson":
Then somewhere along the line, I became aware that the Champion D16 was the correct cross reference for the Knuckle. So, after all those years I was faced with no longer being able to remember which number was right and which was the one I had used for so many years. Have I mentioned lately that its no picnic getting old?
So for the last couple of years, every time I have been asked for a spark plug for a Knuckle, I have not been able to remember which was correct; D14 or D16. That all changed the other day when I was researching something else. I happened to run across this in Palmer's "How to Restore Your Harley Davidson":
- "Of the original Harley-Davidson 18mm spark plugs, the No. 3 is most often used. For a motor used mostly on the highways at fast speeds the No. 4 plug is more desirable."
And a few lines later:
- "A cheap alternative to the No. 3 and No. 4 18mm plugs are Champion D-14 and D-16 spark plugs, respectively."
Kind of reminds me of the old line "I used to think had made a mistake once, but I found out I was wrong." So, as it turns out either the D14 or D16 is an acceptable plug in Knuck, depending on the use.
I do think I have uncovered a small mistake in the Palmer book though. All the catalogs I have show the D16 as the replacement for the No. 3 plug. This is backed up by a Champion spark plug catalog that I have. The D14 is colder than the D16. The confusion no doubt stems from the fact that in Champion's heat range numbering the lower the number the colder the plug, and Harley did it the opposite way. That's a very minor discrepancy given the huge scope of his book. I have trouble not transposing stuff in just one short blog entry! The important thing is that there are interchanges for both the No. 3 and the No. 4 Harley plug.
With that in mind, here is a page from the Knucklehead service manual.
This drawing illustrates spark plug heat ranges pretty well. A spark plug's heat range refers to how well the plug dissipates heat. A colder plug dissipates the heat quicker, and so runs cooler. Therefore, a hotter plug will help keep deposits from fouling a plug if used in an over rich or oil consuming engine. On the other side of the coin, a colder plug will be less prone to overheating and causing pre-ignition in a high compression engine or one that is run hard (Both high compression ratios and prolonged high speed will generate more heat).
Interestingly, the factory manual states that:
- " In some cases best results may be found using a colder plug in one cylinder than the other. In this case it is usually the front cylinder that takes the colder plug as this cylinder is not as likely to foul a plug at low speed."
I've never tried it, but it seems logical enough. So next time you inspect your plugs and find they are not both the came color, it may be worth your while to try a different heat range! Now you know.
In part 1 and part 2 of 68 Inch Racer, I outlined the physical dimensions and bottom end parts for this "dream" motor. In this installment I would like to wrap it up with the top end and valve train.
As to the heads, if I had a set of dual carb Knuck heads laying around (which I do) I would probably use them. After all, if I am going to label this a "racer" then why would I be worried about the leg clearance issue raised by two carbs sticking out the left side of the bike. Intake valves; 2.060". I had a set custom made by Ferrea Racing for a motor I did last winter. Beautiful valves, and no need for a lash cap, but I was disappointed with their limited selection of tulip choices for a 3/8" stem diameter. The only one they offer had more tulip than I wanted, which necessitated shorting the bottom of the guides slightly. It was also quite a bit heavier than I would have liked. Perhaps a 5/16" stem next time with a custom made valve guide.
As to the heads, if I had a set of dual carb Knuck heads laying around (which I do) I would probably use them. After all, if I am going to label this a "racer" then why would I be worried about the leg clearance issue raised by two carbs sticking out the left side of the bike. Intake valves; 2.060". I had a set custom made by Ferrea Racing for a motor I did last winter. Beautiful valves, and no need for a lash cap, but I was disappointed with their limited selection of tulip choices for a 3/8" stem diameter. The only one they offer had more tulip than I wanted, which necessitated shorting the bottom of the guides slightly. It was also quite a bit heavier than I would have liked. Perhaps a 5/16" stem next time with a custom made valve guide.
It goes without saying that the piston domes, exhaust ports and combustion chambers would get the ceramic treatment like this.
Working off a couple of Knuck heads that I have oiled out in the past, it looks as though a head volume of 128 cc is a realistic starting point. Now, if we bore the Knuck heads out for the Pan cylinder's fire ring, we actually increase the head volume by about 5.71 cc's. But of course the fire ring itself will take up most of that increase. The total head volume when bored for the fire ring, but taking into account the amount displaced by the fire ring, calculates to 128.38 cc.
But here is where it gets interesting. The 74" Pan cylinder is shorter than the 74" Knuck by .200" when measured gasket surface to gasket surface (5.530" vs. 5.330). But if you add the height of the Pan fire ring they are the same length. That means that the piston will come to the same point in relation to the gasket surface on the Knuck cylinder as it does to the top of the fire ring on the Pan. But in effect you are lowering the head .200" down by using the Pan cylinder (think of it like shaving the head .200") Now we are talking some compression! When I plug all this into my Engine Analyzer program with a .020 thick copper head gasket, it comes out to 12.26:1 compression ratio. And after double checking all my figures a couple times, it still comes out to that!
Cool. Now we are into race gas territory (68 inch Racer - remember). That kind of compression will allow us to run a fairly radical cam as well. Any time you talk about high performance on a Knuckle engine, in my book there is really only one brand of cam to consider, and that is Leineweber. I am thinking his #3 Knuckle cam. It has .420 lift and 312 degrees of duration, but keep in mind this duration is measured at .020" rather than the customary (for Harleys) .053". That is still probably near 275 degrees duration if converted to .053".
Keeping with the "racer" theme, everything seems to point toward an engine that will not be easy to start. So we might as well add a magneto. I'm envisioning a bike that does not even have a kick starter.
Since this "paper engine" is getting a set of real life vintage dual carb Knuck heads, I would also use a set of real life 40mm Dell 'Orto pumper carbs that I have left over from my first drag bike. They were a little small for the 114" Knuckle, but I suspect they would work well in this application. Since the heads have a 4 bolt Linkert pattern, I would weld flanges onto the Dell 'Ortos to match. Jetting them to run on E85 (85% ethanol) would be really tempting. It has enough octane for this kind of compression ratio, plus the government helps pay for it (with my money). Good luck on getting them to kick in for your $15 a gallon racing gas.
One last thing. If the motor was to be used on the drag strip, then I would leave the valve train open, with no oil going to the top end. This is not a huge advantage, it just simplifies the oiling system and eliminates any clearance issues between spring and cover. But that's the way we used to do it, and it looks pretty cool. For any other application I'd enclose the valve train. Either way I'd use a pre '40 oil pump for the thinner gears and less oil volume in the motor.
That pretty well wraps it up. Did I miss anything? And.... an even better question: will it ever get built?
If you read my post entitled Paper Engines, you will recall that I solved the problem (at least on paper) of building a high compression 61" Knuckle lower end with a 74" top end.
There still are a few things to be considered in the bottom end. For one thing, there is the subject of flywheel weight. That will be partly determined by the end use of this motor. Whether it is for drag racing, "street" racing, Bonneville, flat track, or some sort of road racing. For most of these scenarios, I would lighten the flywheels (the one exception being drag racing with a slick). How much to lighten them is the question. The minimum would be to cut down the heavy left side flywheel to the thickness of the right side wheel.
stock 61" flywheels on left , lightened S&S on right
Since the UL rods are an aftermarket imported item of somewhat unknown quality, I would at the very least have them shot peened. Possibly polished and shot peened. The purpose of polishing is to remove any possible surface imperfections that could lead to a crack. However, polishing also removes the surface left from the forging process which increases the strength of the rod. Shot peening puts that harder surface back on (so to speak). So, just shot peen, or polish and shot peen, but do not polish only!
Of coarse the rod change alone would dictate that the flywheels be balanced, but it becomes even more critical when lightened.
Since the point of this engine is to turn some RPMs, the crankpin and mainshafts are probably not a place to skimp. S&S makes all of the early shafts, including the stepped crankpin, and are probably the highest quality available. Yes the rod set will come with a new crankpin of unknown origin, but that would be better set aside to go in a restoration that will not see such severe service.
This is to be a "Racer" and not a restoration, so why not take advantage of the built in extra strength of Panhead cylinders. Even bored to +.060 (which makes it a true square engine 3.5" bore x 3.5" stroke) the Pan cylinders are undoubtedly stronger than a Knuck cylinder. Sure, there are reproduction Knuck cylinders that are stronger than stock, but they aren't cheap. I would spend the money elsewhere. Besides, there are plenty of Knuck heads out there that have been converted to the Pan headbolt pattern already, so why not use them.
For pistons, I would start with a cheap Pan/Shovel cast piston which is called a 10:1. The dome volume on them is about 52cc which will get some compression ratio (I'll discuss that more when I get to the heads). Once the domes are ceramic coated and the skirts Teflon coated they should work very well.
More to come.
It is probably more common in the automotive field to dream up engine combinations on paper that will likely never be built. Sometimes though, something triggers that urge in my tiny little brain too. Of course, working in the Harley industry, that is usually the type of engine that figures into my daydreaming.
With the recent advent of relatively reasonably priced reproduction UL connecting rods becoming available, those tiny little gears in my head started turning. For me, it is not the designing of a motor with numerous custom (read: expensive) built components that gives me satisfaction. The combination also has to make some sense from a monetary standpoint to make it "cool" in my mind. That obviously stems from some long lost and unrecorded Scotch ancestry. In other words, yes, I am cheap!
With that in mind, I present this for your approval (or disapproval):
With the recent advent of relatively reasonably priced reproduction UL connecting rods becoming available, those tiny little gears in my head started turning. For me, it is not the designing of a motor with numerous custom (read: expensive) built components that gives me satisfaction. The combination also has to make some sense from a monetary standpoint to make it "cool" in my mind. That obviously stems from some long lost and unrecorded Scotch ancestry. In other words, yes, I am cheap!
With that in mind, I present this for your approval (or disapproval):
68 Inch Racer
In the past I have touched on the dilemma of 61" Knuckles or Panheads running cylinders that have been bored to the 74" bore size. Sure you can use 74" pistons with no clearance problems, but with the stroke of the 61" flywheels, the piston will not come to the top of the cylinder, dramatically lowering the compression ratio. This is not really a problem for your typical restoration or Sunday afternoon cruise bike, but to the true gear head, it is an unwelcome compromise.
Besides, what about the legendary "square" motor? (a "square" motor is one with the same bore as stroke) While there may be more hype to it than substance, there still is a certain mystique involved. And with the 3 1/2" stroke of the 61 and 3 7/16" bore of the 74 you are almost there!
As I mentioned above, the availability of UL rods brought this into my mind. The easy way to get that piston to come to the top of the cylinder when using a 74" piston on a 61" flywheel is either a custom made piston with the wrist pin location moved, or a custom made longer rod. Either of those can easily be accomplished if you are willing to spend a lot of money. But like I said, that kind of spoils it for me. But the UL rods are longer than OHV rods. Hmmm.
Here's what it looks like to me:
Stock 61" Knuckle
- Case deck height (center of main bearing race to cylinder gasket surface) 5.380" +
- Cylinder height (gasket surface to gasket surface) 5.405" +
- Fire ring height .120" +
- Base gasket .020"
- = total height of 10.925"
- 1/2 of the stroke (distance from center of mainshaft to center of crankpin at TDC) 1.750" +
- Rod length (center to center) 7.46875" +
- Piston compression height (piston deck to center of wrist pin) 1.625"
- = total height of 10.84375
Subtracting 10.84375 from 10.925 we see that the piston should be about .081" below the top of the fire ring.
Now here is the same calculations on my proposed motor:
68" Racer
- Case deck height 5.380" +
- Cylinder height (74" Panhead cylinder) 5.330" +
- Fire ring height .200" +
- Base gasket .020"
- = total height of 10.930"
- 1/2 of the stroke 1.750" +
- Rod length ( UL rods) 7.90625 +
- Piston compression height (generic 74" piston) 1.415"
- = total height of 11.07125"
Here we see that the piston would come out of the top of the fire ring by about .141". But if we add a .125" "stroker plate" (and another .020" gasket to seal the other side of it) it will put the piston deck about .004" below the top of the fire ring. Just right!
That covers the main configuration, but leaves a lot of details to be discussed. I'll continue this "paper engine" in my next installment.
Have you ever considered what the actual compression ratio of your motor is? Are you sure that you took everything in to account or are you going by the rated compression ratio of your pistons?
The simplest way to measure the actual compression ratio of your engine is to have it assembled, at TDC, and then "oil out" (old school term for measuring the volume) the combustion chamber. But to do this you must also be able to position the engine so that the spark plug hole is at the very top of the chamber so that you don't get an air bubble trapped which would throw off the measurement. Pretty awkward to say the least!
Every other method involves measuring separate components and calculating the ratio mathematically. Here are a couple of things to consider when doing so.
The simplest way to measure the actual compression ratio of your engine is to have it assembled, at TDC, and then "oil out" (old school term for measuring the volume) the combustion chamber. But to do this you must also be able to position the engine so that the spark plug hole is at the very top of the chamber so that you don't get an air bubble trapped which would throw off the measurement. Pretty awkward to say the least!
Every other method involves measuring separate components and calculating the ratio mathematically. Here are a couple of things to consider when doing so.
- cc of a cylinder = diameter x diameter x 12.87 x height
This formula is especially handy for an old time Harley guy like me since you enter the specs in inches, and the constant (12.87) converts the answer to cubic centimeters.
- Head Volume
The normal way to cc a Shovel, Pan or Knuck head is to place a piece of Plexiglas with a small fill hole across the gasket surface. When you do this you will be measuring not only the chamber, but also the space into which the fire ring on the cylinder fits. That means that the volume that the fire ring displaces must be calculated and subtracted from the head volume. Treat the fire ring as a cylinder and use the formula above. To get the cc's of the fire ring it is only necessary to calculate once using the o.d. of the fire ring and then subtract the volume found using the i.d.
- Gasket thickness & gasket bore diameter
Think of it like another really short cylinder and use the above formula to compute the volume.
- Piston deck height
If your piston only comes within .010 of the top of the cylinder, it is just like running a .010 thicker gasket.
- Piston dome volume
This can often be found in manufacturers specs, but not always. You can grease the piston rings, install the piston into the cylinder so that the top of the dome is just below the cylinder top, and then measure the distance down to the deck of the piston. This will serve as the height inserted into our magic formula above, which allows you to use the bore diameter to compute the volume of the cylinder formed from the piston deck to the top (if it did not have a dome in it). Once you have that volume you can oil it out and subtract to get the dome volume.
- Valve stem protrusion
How far the valves were sunk into the heads from previous valve jobs. Now, if you just finished oiling out your heads, this is of no consequence in computing your actual compression ratio. But it will help explain why your compression ratio is not as high as your piston manufacturer claims. Low and behold our handy dandy little formula comes to the rescue again. If you use the valve diameter in the formula along with the amount that the valve is sunk deeper than the minimum spec as the height, you might be surprised how much compression ratio you loose.
[as an example, stock size valves in a Shovelhead when sunk .050" will increase the combustion chamber size by 4.39cc, lowering the compression ratio by about 1/3 of a point]
This is especially relevant on the older motors which usually have a lot of valve stem protrusion and the valve un-shrouding which often accompanies it. In performance applications, the valves often have to be sunk to maintain valve to valve clearance with the hotter cams that are available, so that is also something to take into account when selecting your cam and pistons.
Now perhaps you think all of this doesn't much matter on your average cruiser. Well, maybe. On the other hand, keep in mind that higher compression ratios make a more efficient engine, and thus better fuel economy and power. On the other hand too high a ratio can lead to hard starting and worse yet, pinging. Another consideration is that all cams have a compression ratio range that they will work the best in.
There are a lot of places for a Knuckle to leak oil. Here is a pretty easy and basic tip for assembling Knuckle heads that may help eliminate one.
One thing I see a lot when I dissasemble Knuck heads is that once you remove the rocker boxes, often the lower spring covers (cups) will be loose. Since said cups are held in place by the valve guides, it is an indication that the guide has moved slightly. Obviously if that cup is loose there is nothing to keep oil from running out the bottom.
Lip on guide
What is not so apparent is that the replacement parts available today can be part of the problem! A stock OEM valve guide had a shoulder that measured approximatley .103". The stock OEM lower spring collar had a counterbore in the bottom of it that was approximately .093" deep. That means (if my math skills are still intact) the valve spring would put full spring pressure on the guide, holding it tight down on the cup, and in turn the cup tight down on the head.
Counterbore on lower collar
Unfortunatley, the likelyhood of finding a stock OEM guide is about the same as you stumbling on Elvis' personal Harley (signed under the seat: with love, Prissila). Besides, even if you found the guides, they wouldn't really be the ideal material for use with todays fuels. So it is a given that you will be using reproduction guides.
Here's the problem, though. A typical reproduction valve guide will have a lip that measures only approximately .092". Those of you with higher math skills (or a calculator handy) already see the problem. That's right. The lower collar will no longer hold the guide down, so if the guide moves at all there is nothing to keep the oil from seeping under the lip of the guide and through the guide hole in the cup. True there is still spring pressure on the cup (since the lower collar is now setting on the cup instead of the guide) but that presssure is not concentrated as it should be.
My solution is to machine abut .010" off the bottom of the lower collar. I also use aircraft grade Permatex on both sides of the gaskets that go under the cups, as well as Three-Bond sealer under the lip of the guide itself. While it may be next to impossible to prevent every bit of oil seepage from your Knuckle top end, everything you can do to prevent it is a step in the right direction!
This will be a bit of a rant, I am afraid.
About a week ago I decided to start keeping a record of parts made for Harley Davidson motorcycles that don't fit, don't work and or are just plain shoddy. Believe me (and I am sure you do if you have ever worked on Harleys for a living) this is a constant, ongoing problem in this business. Lately I have had an absolute rash of junk parts to deal with.
I have dedicated a 3 ring binder to this purpose and intend to keep a record of every part I come across that is manufactured incorrectly with the part number, application and manufacturer of the "junk part."
It was really easy to fill up about 3 pages without going very far back in time. I am sure more of the parts I have "beat my head against the wall" about over the years will come to mind and be added as time goes on.
Yesterday I had a four new entries for the book which cost me about a half a day of labor. These were parts that I paid good money for, which were incorrectly manufactured. And this was all just in one section of one motor. Usually the problem does not become evident until you are in the middle of an operation. Did I mention how frustrating this can be? Then to top it off, there are always the added problems. How many hoops will I have to jump through to return the part? Is every one of this particular part from this manufacturer defective? Is there any other source for the part? Can I make the part work with modification? How much time will I waste trying to get any kind of answer from the manufacturer? Does the manufacturer care even a little bit that they are selling junk?
Yeah, a bit of a rant, but you should hear me when the circumstances are fresh. By the way, I titled the 3 ring binder "Book of Shame"
About a week ago I decided to start keeping a record of parts made for Harley Davidson motorcycles that don't fit, don't work and or are just plain shoddy. Believe me (and I am sure you do if you have ever worked on Harleys for a living) this is a constant, ongoing problem in this business. Lately I have had an absolute rash of junk parts to deal with.
I have dedicated a 3 ring binder to this purpose and intend to keep a record of every part I come across that is manufactured incorrectly with the part number, application and manufacturer of the "junk part."
It was really easy to fill up about 3 pages without going very far back in time. I am sure more of the parts I have "beat my head against the wall" about over the years will come to mind and be added as time goes on.
Yesterday I had a four new entries for the book which cost me about a half a day of labor. These were parts that I paid good money for, which were incorrectly manufactured. And this was all just in one section of one motor. Usually the problem does not become evident until you are in the middle of an operation. Did I mention how frustrating this can be? Then to top it off, there are always the added problems. How many hoops will I have to jump through to return the part? Is every one of this particular part from this manufacturer defective? Is there any other source for the part? Can I make the part work with modification? How much time will I waste trying to get any kind of answer from the manufacturer? Does the manufacturer care even a little bit that they are selling junk?
Yeah, a bit of a rant, but you should hear me when the circumstances are fresh. By the way, I titled the 3 ring binder "Book of Shame"
I had been playing around (in my head) with a new slogan to use in my shop. Its based on the old saying "you get what you pay for". Obviously that works to use with persons who think my prices are too high. But, I think there is a danger in having my prices too low (besides not making a living). That would be the perception that if my prices are too low, my workmanship may not be as good as could be obtained at a higher priced shop.
A good example is the "Bare Bones" porting job I offer for Twin Cams. At $499, it is one of the best performance buys on the market for Harleys. When I developed this porting job, it offered outstanding flow for a very reasonable price. With the addition of the knowledge I gained during my week of school with Joe Mondello, they are probably some of the best heads available anywhere for any price! But that still doesn't stop some customers from wanting to upgrade to a more expensive porting job, even though they may not really be in the market for the higher performance potential that the more expensive porting job makes possible.
But now I have seen the other side of the coin. I recently had the displeasure of disassembling a Knucklehead engine that had been "rebuilt/restored" elsewhere. This engine had not been run since its "rebuild", so all of the sins of the rebuilder were plain to see. Though I have never met the person who performed this "restoration", it still nearly made me sick to my stomach to see his workmanship. If there ever was a case of not getting what you payed for, this was it!
Upon pulling the heads, the first problem was apparent. Rust pits in the fresh bore. I am willing to give the benefit of the doubt on this one. Maybe the oil consumption would not be too bad, and perhaps one could justify leaving the bore as small as possible, since it is for a restoration. Yeah, I'd be willing to give him that one, if that was the only thing I found. Pulling the cam cover, though, really told the story. The pinion shaft looked as though it had spent 50 years laying in a swamp before being bead blasted and then sanded. The shaft had deep rust pits over the entire surface. There was a good .002" wear on the end of the shaft that fits in the cam cover pinion bushing. That combined with a pinion bushing that had never been replaced (this was a 1938 engine) came to a grand total of .009" clearance. The factory service manual calls for .0005" (half a thou) to .0012" for that bushing clearance. Nearly 9 times too big!
Bushing end of pinion shaft
And then there are the rocker arms. New standard shafts in worn out rocker arm bores. One of the rockers is worn so badly that a +.010 shaft will not save it. That and rocker pads that show 70 years worth of grooving.
Wear on rocker pad
A good example is the "Bare Bones" porting job I offer for Twin Cams. At $499, it is one of the best performance buys on the market for Harleys. When I developed this porting job, it offered outstanding flow for a very reasonable price. With the addition of the knowledge I gained during my week of school with Joe Mondello, they are probably some of the best heads available anywhere for any price! But that still doesn't stop some customers from wanting to upgrade to a more expensive porting job, even though they may not really be in the market for the higher performance potential that the more expensive porting job makes possible.
But now I have seen the other side of the coin. I recently had the displeasure of disassembling a Knucklehead engine that had been "rebuilt/restored" elsewhere. This engine had not been run since its "rebuild", so all of the sins of the rebuilder were plain to see. Though I have never met the person who performed this "restoration", it still nearly made me sick to my stomach to see his workmanship. If there ever was a case of not getting what you payed for, this was it!
Upon pulling the heads, the first problem was apparent. Rust pits in the fresh bore. I am willing to give the benefit of the doubt on this one. Maybe the oil consumption would not be too bad, and perhaps one could justify leaving the bore as small as possible, since it is for a restoration. Yeah, I'd be willing to give him that one, if that was the only thing I found. Pulling the cam cover, though, really told the story. The pinion shaft looked as though it had spent 50 years laying in a swamp before being bead blasted and then sanded. The shaft had deep rust pits over the entire surface. There was a good .002" wear on the end of the shaft that fits in the cam cover pinion bushing. That combined with a pinion bushing that had never been replaced (this was a 1938 engine) came to a grand total of .009" clearance. The factory service manual calls for .0005" (half a thou) to .0012" for that bushing clearance. Nearly 9 times too big!
Bushing end of pinion shaft
Splitting the cases revealed that the roller bearing surface of the pinion shaft was just as rust pitted as the rest of the shaft. It may have lasted a few hundred miles before disintegrating, but other things would have prevented the engine from ever running that long.
Roller bearing surface of pinion shaft
The cam was in similar shape. Lots of pitting on the cam lobes, along with .009" bushing clearance on one end and .006" on the other. Pulling the oil pump revealed a decent body and gears, but a pressure relief spring that may have come out of a ball point pen rather than the correct one. The check valve spring looked to be 70 years old, and in case it never dawned on you, springs do tend to loose some pressure with time.
About the only clearance that I found that was not way too big, was the valve to guide. And that was way too small! All four valves were fit at .001 clearance. Now, with the huge pinion bushing clearance and the way too weak pressure relief spring, there is no chance that the oil pump could have built enough pressure to get any oil to the heads, so the valves would have stuck anyway. However, at .001" valve to guide clearance on a Knuckle, it would not have mattered if the valves were submerged in oil, they would have stuck!And then there are the rocker arms. New standard shafts in worn out rocker arm bores. One of the rockers is worn so badly that a +.010 shaft will not save it. That and rocker pads that show 70 years worth of grooving.
Wear on rocker pad
Like I said, it is enough to make me sick to my stomach. Work like this goes far beyond incompetent. Its is down right theft to charge any amount of money for this type of work!
You get what you pay for. Well, that is not always true. The person who did this to this engine proves that sometimes, no matter how low the price, you will not get any value for your money. I try to be at the opposite end of the spectrum. I do my very best to give the customer his money's worth and more no matter how high (or low) the price.
(some of this post is taken directly from an answer that I posted on the FlatHeadPower bulletin board in response to a question about what was the customary way to modify stock Knuckle heads for a 2" intake valve. I thought I would add a little more info and make it a post here)
note the keeper groove is only squared on tip end
Vintage hot rod Harley's ....you gotta love 'em! And one of the most popular motors to "hot rod" in times past was the venerable Knucklehead. If you have been around Harleys long enough, you have likely heard the stories, some might even say legends, of somebody that had a Knuckle that would "whup" anything around. Seems that every locality has at least a few of these stories that the graybeards can relate with a little prodding. Like all legends, the stories likely had their roots is some degree of fact.
So, what made these hot rod Knuckles so fast? Like every good motor, it was a combination of the right parts and the right modifications. Some of the most popular mods included installation of Flathead flywheels for an increase in stroke. Along with the flywheel change, often the flywheels were lightened to increase the rate of acceleration. A surprising number of Knuck heads were modified to run dual carbs. Cams could be re-ground for more lift and duration. And then there was porting and polishing along with an oversize intake valve. This last modification, the oversize intake valve is what I would like to focus on in this post.
A vintage modified dual Linkert Knuck
Back in the old days, the usual way to install a big intake valve in a knuck was to remove the old seat insert and grind the new seat right into the cast iron of the head (like an iron head XL). When you do it this way, a 2 inch valve is barely big enough, and many of them used a 2 1/32" or larger valve. For good flow you want the "choke" under the 45 degree seat to be a maximum of about 90% of the valve head diameter. If the stock seat insert is 1.875, then you can see that even the 2 1/32" valve would leave too large a diameter hole (90% of 2.031 is 1.828). On the other hand, low lift flow will likely be a bit better with the "too large" diameter under the valve, and lets face it, street knucks are for the most part limited to low lift. A bigger problem with using a 2" valve directly onto the cast iron might be any misalignment between the guide and the machining for the seat insert. If they are not close to concentric, there may not be much of the valve "catching" the head on one side.
valve seat cut onto cast iron of head after seat insert removal
A 2 1/32" (2.031) intake valve may have been the most common size used in the "old days" but there are some other considerations also. The valve pocket in the piston may not be large enough to give clearance around the edge of the valve. Even though you will likely be using a Shovelhead piston, remember that those will have been manufactured with a 1.940" (1 15/16) valve head diameter in mind. That means that if your intake valve and piston are coming close enough to each other (remember the intake valve will begin to open before the piston even reaches TDC) then even if there is plenty of depth to the piston valve relief, it may not be of sufficient diameter. The edges of the valve reliefs in the pistons can be opened up easily enough with a die grinder, but machining them on a mill will give a much more professional look.
A 2 1/16" (2.0625) intake valve will come closer to the ideal size for cutting the seat directly into the head (at least from a flow standpoint), but if you are still running a 3 7/6" bore, then opening the diameter of the valve relief in the piston will put you perilously close to cutting into the top ring groove. With anything larger than a 1.94"intake valve it would be a really good idea to mock up the motor with clay in the valve reliefs on the pistons. That way after you have gently rotated the engine a couple revolutions, you can see (and measure) the actual valve to piston clearance via the flattened clay. Don't forget that it is best to use light springs on the valves to avoid deflection of the valve train during this check.
Many of the large valve conversions done in times past used what I assume to be a tractor valve. That involved cutting down the valve head diameter as well as cutting a new keeper groove to shorten the valve. If you have to shorten the stem, then you should use a lash cap so that the rocker pad has a hardened surface to ride on. The added thickness of the lash cap should be considered when determining valve length. Whatever valve is selected should have a fairly minimal tulip or you will have to shorten the bottom of the guide for clearance (something a knuck can little afford; the knuck guides are already too short for good longevity!)
An example of a valve that will work (though far from ideal) is a Perfect Circle (brand name) 211-2455. It is a 2 3/32" with a 3/8" stem and not much of a tulip. The stem length is plenty long for mounting in a lathe to cut a new keeper groove. This valve also has a 30 degree seat angle rather than a 45. If you plan to use a 30 degree seat, then you are already there, but with the extra diameter there is enough material to allow you to grind it to a 45. One of the drawbacks to this valve is that the stem diameter is actually .3725". A stock Knuckle intake valve will have a stem diameter of approximately .375" so unless you are using guides that leave a little extra meat in the I.D. for fitting, you will likely wind up with more clearance than you might want.
When machining an oversize valve for use in a Knuckle, your first steps would be to cut the head diameter to size, grind the 45 degree seat on the valve, and then reduce the margin (which will have become wider due to cutting down the diameter) back by cutting the face of the valve. Once you have all of that taken care of, you are ready to cut the new keeper groove. You will want to mount the valve in the lathe by the stem end and cut the groove as close to the chuck as possible to keep everything concentric. The groove only needs to be "squared off" on the top edge, since that is where the spring pressure will apply force to the keeper. The very last step is to actually shorten the valve. This can be most easily accomplished by cutting the stem an appropriate distance above the new keeper groove with a cut-off wheel, leaving a small amount of extra material to face off on your valve grinder's valve stem tip refacing wheel. Don't forget to take into account the height of the lash cap, and where it will ride in relation to the valve keepers, when determining where to cut the valve.
note the keeper groove is only squared on tip end
Rowe replacement Knuckle intake has overall length of 3.575" with about .090 of that being the margin. I have cut 2.060 intake valves for use in Knucks using 3.585 as the overall length with .050 of that being the margin. This length does not take the needed lash cap (Crane # 99422-16) into account; it will add .060" to the effective length. If you are working from scratch, the 3.585 length (or 3.645 if you are having custom valves made: 3.585 + lash cap) may be a good place to start. If you start with the same length as a stock valve you will have to sink the valve quite a bit to get the stem protrusion in the ballpark for proper rocker arm geometry, and that will lower the compression ratio and tend to "shroud" the valve hurting flow.
Another option would be to install an oversize seat insert and use a 2" iron XL valve. This valve is readily available as a 1/16" oversize for a '70 to '84 XL. It is approximately the right length, so you don't have to mess with shortening or lash caps. The drawback is that you need to come up with a 5/16" I.D. valve guide and suitable springs, top collars, or keepers. The FHP knuckle heads used an "off the shelf" 1 15/16" XL intake valve, but I never did see where they offered the guides for 5/16" stem in any oversizes. Their spring kits should work for such an application, though the lower collar may be a problem.
But is this type modification worthwhile at this late date? That depends. By far the majority of Knucklehead owners today are just thrilled to have one to ride. Many would probably be horrified that anyone would consider modifying an otherwise stock Knuckle head, despite the fact that this particular mod can't be detected externally. Of course all of these modifications can easily be applied to any of the reproduction Knuckle heads, such as those from V-Twin and those from Flathead Power (now part of S&S). And, there are always those people who just can't leave things alone. I am one of those. There is hardly an engine I own that has not been modified for more power, and just being a priceless antique is not enough of a deterrent to keep me in check. Are you one of those people too?
If your goal is to build a Knuck that will dominate everything around, just as those of legend did ....well, that probably isn't going to happen. On the other hand, there are a whole world of bikers out there who will be totally blown away by just how strong your Knuckle can run! In my book, that is just one of life's little pleasures.
Since the title of this blog is Knucklehead Theology, you are probably wondering why so little has been said about Knuckleheads so far. Not to worry, having owned and ridden Knuckleheads for over 25 years, and drag raced them for about 15, there is plenty to come.
Today I would like to talk a little bit about Knucklehead cylinders. We have all heard the horror stories of broken Knuck cylinders. And it is my guess that there are nearly as many theories as to why they break, as there are those stories. I am not going to claim to have the definitive answer, only theories of my own. This is one that I would love to have comments from others with their own thoughts.
The first time I saw a knuckle cylinder break, was while attending Motor Cycle Mechanics school at Hutchinson Area Vocational Technical Institute in about 1979. One of the other students (a Triumph guy) had brought in a Knuck chopper to work on for a friend of his. The engine that he had was a 61", but it had cylinders that were bored out to 74" plus. I don't recall exactly how much plus they were, but it would not surprise me if they were +.060 or +.070.
That is not unusual to find, but it does leave you with very low compression. There are no 74" bore pistons that are made for a 61" stroke (at least not that I have ever found), which leaves you stuck running normal 74" pistons. The only problem with that is due to the difference in wrist pin location and stroke between them, the 74" piston will be nearly a 1/4" lower at TDC than a 61" piston. (61" is 3 1/2" stroke/ 74" is 3 31/32")
Don't know if it was the owner's idea, the student's idea, or the instructor's idea, but someone's solution was to shave material off the base gasket surface to get the pistons closer to the top. I winch just thinking about it now. One wrinkle was that before the engine was assembled, another student bought the bike! The results were predictable. After the new owner finished assembling the engine, during initial start up, one backfire while kicking broke the cylinder off at the base! As a side note, the new owner bought a set of used 61" cylinders which were also at a 74" bore. He rode the bike for one season, and then sold me the knuckle engine when he bought a new "crate" Shovelhead motor. I ran that engine for many years and many, many miles with that ultra low compression.
The next time I had occasion to see an "exploded" knuckle cylinder, was a case of being in the right place at the right time. I happened to pull up to a stoplight behind another knucklehead. As the rider attempted to pull away in a quite normal manner, his front cylinder lifted. Of course I pulled over to see if I could lend a hand. This was in about the mid 1980s, so my memory is less than clear, but I do believe that the part of the piston which unfortunately was now in full view, was badly scored.
Fast forward about 10 years. While not a knuckle, the next broken cylinder that I remember seeing shares some similarities. This was on an old Pan/Shovel stroker belonging to one of the owners of the shop I worked for at the time. It had a set of +.070 stock cylinders. This one I took personally, because I had recently bored the cylinders. This one too had a badly scored piston skirt. (I believe that the scoring was due to the cylinders being powder coated after boring them which may have distorted them)
Soon after this, another acquaintance on his knucklehead had a cylinder explode while accelerating from a stop sign. As best as I can recall, this also had a badly scored piston. (I do not believe that I had anything to do with building that motor)
It should be obvious by now that all but the first incident that I related had one thing in common (at least if my memory serves me). That, of course is that in each case the broken cylinder was accompanied by a scored piston. As far as I know, they all shared one other thing in common; a large overbore on the cylinders.
Somewhere along the line a customer brought me a set of +.060 Knuckle cylinders to check for him. Looking at the bore I found something quite interesting. The bore had actually turned blue between the fins. Honestly, you could see where the fins were from the inside because the spaces between them was blue! For years after this I avoided boring Knuckle cylinders more than +.050. I just knew that if the cylinders were thin enough to turn blue like that, they had to be on the verge of exploding.
I am not so sure anymore. Over the years I have had the pistons score badly on my wife's 61" Knuckle numerous times, for numerous reasons. At least one set can be chalked up to the manufacturer. I saved the little instruction sheet that came with the pistons which called for .001 clearance. A couple more sets of identical pistons gave similar results. Then another set of identical pistons came with a similar little instruction sheet which called for .003 clearance. Oops! Another set went because we went for a weekend trip with a group of friends when the engine was fresh, the weather hot, and the speeds excessive. Another I attribute to a burned out head gasket sucking air. Well, you get the idea. But no matter how many pistons we scored with that 61", the thick cylinders held up fine.
Maybe I should point something out here. When I speak of a "scored" piston in a Harley, it is in reality a piston that has seized. The reason that in most cases the engine does not stop, is because of the extreme weight of the Harley flywheels. If pistons "scored" like this in any other motorcycle engine the motor would be stuck tight. Understanding that this piston scoring phenomena is actually a piston seizing phenomena should really shed some light on the broken knuckle cylinder issue.
Add to this, some anecdotal evidence from my 74" Knucklehead. I have run it for many years at +.050. I never was willing to bore to +.060 for the above mentioned reasons. Each time I have had it apart, I have honed it to bring it back to straight and round. I think that the last time I put it together it was with about .008 clearance on a set of high compression cast pistons. Never a bit of problem, and I run it very hard!
So here is the big question. Are the stock Knucklehead cylinders just too weak to be safe when bored much oversize? Or is the real culprit the mechanic that set them up too tight, causing it to seize? Well, before you go blaming your local mechanic, keep in mind that he probably sized your cylinders to specifications. Its not really his fault if factory specs give bad results, particularly if he does not do many Knuckleheads. Furthermore, too tight set up specs is only one possible reason for your pistons seizing. Anything that adds too much heat, or removes too much oil can give the same results. (think timing, idling in traffic, oil breakdown, etc.)
Are the "cheap" reproduction cylinders prone to breaking too? I really don't know. Some would say that they are. Part of the problem is that most of the information we have will be anecdotal (I can't believe that I am actually going to use that word twice in one day). Since a failure like this tends to be catastrophic, most who experience it once will be leery of taking any chances of it happening again. My guess is that if you had a +.070 break on you once, you would be sure to replace it with one as close to standard as possible rather than making some adjustment and using another +.070.
Today I would like to talk a little bit about Knucklehead cylinders. We have all heard the horror stories of broken Knuck cylinders. And it is my guess that there are nearly as many theories as to why they break, as there are those stories. I am not going to claim to have the definitive answer, only theories of my own. This is one that I would love to have comments from others with their own thoughts.
The first time I saw a knuckle cylinder break, was while attending Motor Cycle Mechanics school at Hutchinson Area Vocational Technical Institute in about 1979. One of the other students (a Triumph guy) had brought in a Knuck chopper to work on for a friend of his. The engine that he had was a 61", but it had cylinders that were bored out to 74" plus. I don't recall exactly how much plus they were, but it would not surprise me if they were +.060 or +.070.
That is not unusual to find, but it does leave you with very low compression. There are no 74" bore pistons that are made for a 61" stroke (at least not that I have ever found), which leaves you stuck running normal 74" pistons. The only problem with that is due to the difference in wrist pin location and stroke between them, the 74" piston will be nearly a 1/4" lower at TDC than a 61" piston. (61" is 3 1/2" stroke/ 74" is 3 31/32")
Don't know if it was the owner's idea, the student's idea, or the instructor's idea, but someone's solution was to shave material off the base gasket surface to get the pistons closer to the top. I winch just thinking about it now. One wrinkle was that before the engine was assembled, another student bought the bike! The results were predictable. After the new owner finished assembling the engine, during initial start up, one backfire while kicking broke the cylinder off at the base! As a side note, the new owner bought a set of used 61" cylinders which were also at a 74" bore. He rode the bike for one season, and then sold me the knuckle engine when he bought a new "crate" Shovelhead motor. I ran that engine for many years and many, many miles with that ultra low compression.
The next time I had occasion to see an "exploded" knuckle cylinder, was a case of being in the right place at the right time. I happened to pull up to a stoplight behind another knucklehead. As the rider attempted to pull away in a quite normal manner, his front cylinder lifted. Of course I pulled over to see if I could lend a hand. This was in about the mid 1980s, so my memory is less than clear, but I do believe that the part of the piston which unfortunately was now in full view, was badly scored.
Fast forward about 10 years. While not a knuckle, the next broken cylinder that I remember seeing shares some similarities. This was on an old Pan/Shovel stroker belonging to one of the owners of the shop I worked for at the time. It had a set of +.070 stock cylinders. This one I took personally, because I had recently bored the cylinders. This one too had a badly scored piston skirt. (I believe that the scoring was due to the cylinders being powder coated after boring them which may have distorted them)
Soon after this, another acquaintance on his knucklehead had a cylinder explode while accelerating from a stop sign. As best as I can recall, this also had a badly scored piston. (I do not believe that I had anything to do with building that motor)
It should be obvious by now that all but the first incident that I related had one thing in common (at least if my memory serves me). That, of course is that in each case the broken cylinder was accompanied by a scored piston. As far as I know, they all shared one other thing in common; a large overbore on the cylinders.
Somewhere along the line a customer brought me a set of +.060 Knuckle cylinders to check for him. Looking at the bore I found something quite interesting. The bore had actually turned blue between the fins. Honestly, you could see where the fins were from the inside because the spaces between them was blue! For years after this I avoided boring Knuckle cylinders more than +.050. I just knew that if the cylinders were thin enough to turn blue like that, they had to be on the verge of exploding.
I am not so sure anymore. Over the years I have had the pistons score badly on my wife's 61" Knuckle numerous times, for numerous reasons. At least one set can be chalked up to the manufacturer. I saved the little instruction sheet that came with the pistons which called for .001 clearance. A couple more sets of identical pistons gave similar results. Then another set of identical pistons came with a similar little instruction sheet which called for .003 clearance. Oops! Another set went because we went for a weekend trip with a group of friends when the engine was fresh, the weather hot, and the speeds excessive. Another I attribute to a burned out head gasket sucking air. Well, you get the idea. But no matter how many pistons we scored with that 61", the thick cylinders held up fine.
Maybe I should point something out here. When I speak of a "scored" piston in a Harley, it is in reality a piston that has seized. The reason that in most cases the engine does not stop, is because of the extreme weight of the Harley flywheels. If pistons "scored" like this in any other motorcycle engine the motor would be stuck tight. Understanding that this piston scoring phenomena is actually a piston seizing phenomena should really shed some light on the broken knuckle cylinder issue.
Add to this, some anecdotal evidence from my 74" Knucklehead. I have run it for many years at +.050. I never was willing to bore to +.060 for the above mentioned reasons. Each time I have had it apart, I have honed it to bring it back to straight and round. I think that the last time I put it together it was with about .008 clearance on a set of high compression cast pistons. Never a bit of problem, and I run it very hard!
So here is the big question. Are the stock Knucklehead cylinders just too weak to be safe when bored much oversize? Or is the real culprit the mechanic that set them up too tight, causing it to seize? Well, before you go blaming your local mechanic, keep in mind that he probably sized your cylinders to specifications. Its not really his fault if factory specs give bad results, particularly if he does not do many Knuckleheads. Furthermore, too tight set up specs is only one possible reason for your pistons seizing. Anything that adds too much heat, or removes too much oil can give the same results. (think timing, idling in traffic, oil breakdown, etc.)
Are the "cheap" reproduction cylinders prone to breaking too? I really don't know. Some would say that they are. Part of the problem is that most of the information we have will be anecdotal (I can't believe that I am actually going to use that word twice in one day). Since a failure like this tends to be catastrophic, most who experience it once will be leery of taking any chances of it happening again. My guess is that if you had a +.070 break on you once, you would be sure to replace it with one as close to standard as possible rather than making some adjustment and using another +.070.
Well, it looks as though I am going to have to make this into two posts. In the second half I will offer my thoughts and attempt to offer some solutions. In the mean time, I would love to hear from any of you who have had Knuck cylinders break, and the circumstances.
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