camshaft end play

[mike zahorik]

I'm refreshing my 1926 engine. Today I checked the camshaft end play and found it to be 0.029". This seems on the long side. I don't know what it should be, but I had expected less. This end play must affect the valve timing and the ignition to some extent. I use a timer and run on magneto 99% of the time. The engine was rebuilt about 8 years ago, which is about 20k or more miles. At that time the cam bearing were new and a new Stipe 280 cam was installed. I checked the lift and found that it is still very close to spec, many 1 or 1.5 thou off. I believe the cam is still in good shape. Do the cam bearing control this? Thanks Mike

[mike zahorik]

Also, the gear lash is fine. When the engine was rebuilt, the crank gear was replaced and the cam gear is aluminum which was replaced new about 4 years ago. Mike

[Les Schubert]

Usually you get a NASTY rattle that resembles a rod but it is erratic

[mike zahorik]

I think I can hear it when I spin the crankshaft, no pistons in yet. Mike

[mike zahorik]

Well...... this is interesting. I removed the camshaft and found that the front bearing to the camshaft clearance is about 0.008". Turns out that the center pin bearing bolt is rather snug in the center bearing, but the front pin bearing bolt is sloppy. The pin is about 0.305" diameter, whereas the center bolt pin one is 0.312" and the front bearing bolt pin hole is also sloppy. So it looks like most of the camshaft run out is from locating pins and associated holes. Mike

[Scott_Conger]

Pretty common. Fix the pin and move on. Clearance of .008" isn't bad for a refresh.

You can see how one clever fellow fixed that issue years ago, here: https://www.mtfca.com/phpBB3/viewtopic.php?f=2&t=5419

Not what I'd do, but pretty clever none the less.

[mike zahorik]

I think that the pin gets hammered by the camshaft moving back and forth. I was leaning toward adding material to the pin. Either with weld or braze. Then fitting the pin to the wallowed out hole. The cam bearing is still good and don't want to change it just for a better hole. Mike

[Scott_Conger]

That's what I'd do

[mike zahorik]

I just took apart the front cam bearing to get a better look at the hole and it appears that a 21/64" bit fits nearly perfectly in the hole. I wonder could there have been two different size pins used on this engine? I looking in Lang's catalog and they do not mention it. Mike

[Norman Kling]

About 10 years ago I had the same problem and I just put a bit of brass shim stock in the hole and screwed in the bolt. It has held since and has not had a knock.
I don't think the difference in valve timing would be noticeable and would not affect the ignition timing if you set it to spark just after the piston reaches top dead center. The spark lever will take up for any variations in ignition timing.
Norm

[mike zahorik]

Sounds like a good idea, I'll try it. Thanks Norm. Mike

[mike zahorik]

I tried rolling in a 0.004" Steel shim around the hole. Installed the cam, bearings and the better pin in the front bearing. The end play is now down to just under 0.010" That's a 0.020" improvement. I think I have the solution. Thanks a million. Mike

[Dennis Prince]

Has anyone tried using the thrust washer kit to take up the end play? I was thinking that might be a way to get rid of the excess play if the pin hole is worn in an egg shape.

[Dennis Prince]

Has anyone tried using the thrust washer kit to take up the end play? I was thinking that might be a way to get rid of the excess play if the pin hole is worn in an egg shape.