Board index Flathead Power-Technical Questions, Answers, and Suggestions Knuckles Genny shovel cam vrs knuckle cam

Genny shovel cam vrs knuckle cam

Moderators: Curt!, Pa

Post Thu Jan 22, 2009 9:39 pm

Posts: 514
Anyone have one of each or know of a site that has measurements on how far the lobes are placed on the shaft.
Trying to see just how different they are with respect to lobe placement, I think the ends and the gear is the same.
TIA. :shock:

Post Thu Jan 22, 2009 10:25 pm

Posts: 387
Why do you want to know? Panhead and Shovel cams have the same lobe placement, Knuckle is different and tomorrow I could tell you by how much. However, it is about a half width of the lobes plus or minus. Knuckles also have a different rocker arm ratio so the lift and shape of lobes is quite different.
Robbie

Post Sat Jan 24, 2009 6:37 am
Also: with the knuckle cam the bearing journal on the crankcase side is slightly smaller on its OD since it fits into a bronze bushing and not a needle roller like the later Shovel cam. HD used to allow .001 to .003" clearance with the needle roller so using the smaller OD knuckle cam in the needle roller (Torrington) shouldn't be a problem so long as you are still within specs. Both my Andrews knuckle cams measured .001" smaller on the OD than a comparable shovel cam so the difference for me was very small and I was well within spec.

Post Sat Jan 24, 2009 5:40 pm

Posts: 514
So Brent, you have done this conversion?

Post Sat Jan 24, 2009 6:38 pm
Yes on my own personal knuckle. I used an Andrews cam (designed for the oe bushing in the case) with the later Torrington needle bearing. The Andrews cam journal was .001" smaller than the standard Shovel journal. Once I installed the needle bearing in the case I checked its ID with a plug gauge I had made up (the only way to really accurately check the ID of a needle bearing). The running clearance I ended up with was .002" (well within the .001-.003" HD used to allow). Now keep in mind, if the interference fit in the case is a little tighter than normal, the ID of the needle bearing will be reduced, effectively diminishing your running clearance. Not a big deal so long as you check the ID with a plug gauge. On the flip side, if the interference fit is a little loose (eg: the bearing housing ID is too large) the needle bearing id (once installed) will be a little larger increasing your running clearance. So long as you are within the range you should be OK. Better a little loose than tight - been many a cam journal destroyed by a "tight" needle bearing in the case. Be sure to measure your cam journal properly though - I am going by what Andrews produces and did not have a stock Knuckle cam journal to compare it too. Andrews says their journal size is machined for a stock type bushing but.....?

Hope this info helps.

Brent

Post Sat Jan 24, 2009 7:00 pm

Posts: 514
Yes it helps greatly.
So what yr is your lower end, and are u running stock lifter bases for the shovel.
One last, how are u getting the top oil back down to the lower end

Post Sun Jan 25, 2009 8:12 am
My cases are S&S knuckle cases with the needle roller cam bearing. Are you putting a shovel top end on a knuckle bottom end? I am not quite clear on what it is you are going to do. Let me know. Thanks.

Brent

Post Sun Jan 25, 2009 5:03 pm

Posts: 514
Actually just the opposite, knuck top (altered for pan jugs, many were butchered, thanks moco) on genny shovel bottom.

Post Sun Jan 25, 2009 7:02 pm

Posts: 387
Now you are into a bag of worms! What lifter blocks are you using? If you use pan/shovel blocks the lifters won't hit the cam lobes correctly on a knuckle cam. If you use a pan/shovel cam you lose a large portion of your lift due to different rocker arm ratios! Knuckle rocker arms operate at a 1:1 ratio, Pan/shovel nominally at 1.5:1, a major difference. Pushrod angles are different as well. You can run into all sorts of interference problems with the wrong combo. Knuckles also return top end oil using crankcase vacuum down the pushrod tubes. Pan/shovel cases don't have the oil passages in them to accomplish this or the breather passage holes. Pan/shovel top ends drain by gravity. Are you sure you want to do this? It does not involve just bolting parts together!
Robbie

Post Sun Jan 25, 2009 8:14 pm

Posts: 514
Robbie, doing research now, and will have shovel cam with lobes like a knuck,, maybe talk to andrews or SNS, on that. Planning on shovel lifter blocks,(maybe drilled drain holes to next size) and draining oil back down through them. Have been told shovel also has vacuum on down stroke like knuck. Top feed about the same. Knuckle lifter blocks won't bolt up, and don't want to drill cases. I know it's a challenge, but have seen it done with nosecone shovels.

Should be able to use panhead or shovel jugs with this config. don't you think.

Post Tue Jan 27, 2009 6:36 am

Posts: 514
Back to original question, when comparing the ramp and lobe on the shovel to the knuck cam is there less material because of the rockers, and what other difference?

Also since the heads have been re leaved for the fire ring on the jug, instead of using panhead jugs, I could use shovel
and figure out how to get some top oil to drain back down that way.

Post Thu Jan 29, 2009 10:48 pm

Posts: 514
So, no good ole boys able to give a guy a few pointers?

Post Fri Jan 30, 2009 7:04 am

Posts: 1634
?? don't understand your last post. It seems to me that you are getting plenty of information, but haven't properly defined the question.

what are you trying to do, exactly? It does sometimes appear that people build, or try to build, engines from mismatched parts for no useful reason, simply because they think it would be 'cool' in some way. That knuckle/pan/shovel engine is the ultimate example. Harley developed these engines over time for engineering and marketing reasons, some parts interchange, some don't, some can be made to fit but it's not worth the trouble.

I think the essential points - regarding rocker arm ratios, valve block angles etc - have been covered. The answer seems to be that this particular combination of parts isn't viable. You could probably make it 'sort of' work with enough machine shop time, but it would be such a personal thing that maybe no-one knows the answer
Shoot, a man could have a good weekend in Dallas with all that stuff...

Post Fri Jan 30, 2009 8:52 am

Posts: 639
Location: Wisconsin, USA
ULHer, I would suggest you have a cone motor cam reground to knuck spec. Someone once told me they used a Leinwebber J-3? cam in a similar motor and it ran ok, but I never compared to a stock knuck cam. The shovel cylinders will not bolt up to the knuck heads. You can used untimed crankcase vacuum to return top oil but it helps to have a pcv type one way valve in the line. You can use a fitting in the timing plug hole as S&S did with their prototype sidewinder motors or tap in above the crancase oil return trough at the top of the rear motormount. A board member, wawilhelmo, or something like that, has built a shovel bottom with knuck top bike. You may want to look him up in the member list and see if he will help you out.

Post Fri Jan 30, 2009 3:46 pm

Posts: 514
amklyde wrote:
ULHer, I would suggest you have a cone motor cam reground to knuck spec. Someone once told me they used a Leinwebber J-3? cam in a similar motor and it ran ok, but I never compared to a stock knuck cam. The shovel cylinders will not bolt up to the knuck heads. You can used untimed crankcase vacuum to return top oil but it helps to have a pcv type one way valve in the line. You can use a fitting in the timing plug hole as S&S did with their prototype sidewinder motors or tap in above the crancase oil return trough at the top of the rear motormount. A board member, wawilhelmo, or something like that, has built a shovel bottom with knuck top bike. You may want to look him up in the member list and see if he will help you out.

1. Thanks for the input amklyde, I know you love the genny shovel.
2. I have been told to drain top oil back to port that would normally suck oil out of primary if u didn't have a sealed primary.
3. The heads are coverted to accept pan cyls. something done to many in the 60s. because lack of knuck cyls. I'm thinking
of using shovel cyls, since they are about the same as pans.
4. The cam I end up with and will be the most modified /custom part would be a genny shovel with lob profiles like an
Andrew K syle, used in the knuck.
Thanks all for your help, this will be a learning experience for sure. Have already learned a lot about how the return oil
and haven't turned a wrench yet:)

Post Fri Feb 06, 2009 7:15 pm

Posts: 150
Location: Carver, MN

Just my 2 cents, but;

Knuckle cam is about .350 lift (if Andrew's stock Knuck cam is correct) If you multiply that by the shovel rocker ratio of 1.43:1 you will see that a shovel cam of .500 lift will give about stock Knuckle lift when used with the Knuckle 1:1 rockers. Now pick the shovel cam with the most duration you can find for that lift, cause you will need it if the Knuck heads have been bored for the whole .200" firering height. (think of it like shaving the heads .200")

Your best bet for returning the oil from the top would be external drains from each individual spring cup. Then you may be able to drill the drain holes in the shovel lifter blocks enough to drain the rocker boxes alone. The pushrod tubes will be difficult to seal though, since the seat for the cork on the lifter blocks will be at a different angle than the ones on the rocker boxes. I have had a guy say he had success with cutting a cork at an angle, but that seems pretty mickey mouse to me.

Lot's of Knuck heads had the one headbolt hole moved to accept a pan cylinder, but unfortunately that same headbolt is even farther away on a shovel cylinder and there is not enough material in the head to do that mod.

I'd recommend nailing down the compression ratio before getting too far into the project, but all in all, the oil return is the biggest issue. Plenty of conversations on this board about that, including restricting the oil feed. Good luck with your project

Post Sat Feb 07, 2009 2:42 pm

Posts: 514
Thanks Lee, you gave me some things to ponder, that's for sure. One thing that would help is have a shovel cam ground
like a knuck, that would take care of the problem.
Have seen guys do this mod on late shovel/nosecone motor, seems would have same issue with shovel blocks.

Post Sun Feb 08, 2009 12:32 pm

Posts: 150
Location: Carver, MN

I am not sure I explained my comment well enough ULHer. What I meant is that the Shovel cam is not much of a problem with this set up. As I said, any Shovel cam that is advertised as .500" lift will give about the same lift as a stock Knuckle cam. The Difference will be in the duration. If you are running more than stock compression ratio, then you want extra duration anyway. Just how much duration will depend on the compression ratio that you end up with. That's why I recommend figuring out your compression ratio first. Not enough compression ratio for the cam grind will make the engine a dog, but too much compression for the cam will make the engine hard starting and prone to detonation.

Some of the things you need to know are: head volume, piston dome volume, compression height of piston (wrist pin location in relation to piston deck), bore, stroke, and rod length. Since this is not a stock application, the advertised compression ratio of the piston will not be of much help.

Post Sun Feb 08, 2009 9:46 pm

Posts: 2684
Location: Los Angeles, CA
Leinweber will make any kind of cam you want.
http://www.leinewebercams.com/

Post Mon Feb 09, 2009 6:32 am

Posts: 514
Yes Chris, you are correct. I spoke to Jim a week ago about this build.

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