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OS 120III Pumped Cam/Cam follower alignment

Old 06-20-2015, 08:31 AM
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Champ-RCU
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Default OS 120III Pumped Cam/Cam follower alignment

With the push rod tubes removed, cam and cam bearings still in place with cam followers removed ; should the cam lobes be aligned directly centered under the cam follower tubes?

With this engine I have a very LOUD snap as the intake valve closes. Placing my finger on the rocker arm as I rotate the crank as the intake valve closes I can feel the snap as well. I have removed the cam follower and cleaned it with OOOO steel wool oiled it well and replaced, snap still there. However when I looked down the cam follower tube w/o followers , I noticed that the cam is shifted to the right about half the width of the cam lobe. It appears that at best only the outer half of the cam is in contact with the follower. Is it possible that the cam is not the correct one for the engine? Could this apparent misalignment cause a binding of the cam follower which leads to the snap?

Yes I did purchase this used here on RCU. Person I got it from said it did not have the noise last time the engine was run. The internals, crank, bearings, piston and rod look new. No corrosion at all. The RCU'er I got it from is a standup kind of guy and is willing to refund my $. However this thing intrigues me and I would like to get it running smoothly.

Any suggestions would be appreciated.


Thanks in advance,

Mark
Old 06-22-2015, 06:14 AM
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Bax
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The dot on the camshaft will align with the pushrod tubes when the piston is at top-dead-center. Please see the photo below:

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Old 06-22-2015, 09:47 AM
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Champ-RCU
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Originally Posted by Bax View Post
The dot on the camshaft will align with the pushrod tubes when the piston is at top-dead-center. Please see the photo below:

Bax, thanks for the answer, however that is not what I'm talking about. The timing of the cam is as shown.

Imagine that the head, valve push rods and tubes are removed, the cam followers are removed and you are looking into the tubes where the cam followers just came out. Now you can see the cam thru those tubes. Correct? In this engine when I look at the lobes of the cam thru the cam follower tubes, (Don't know if that is the proper word for the part of the case the cam followers reside.) it appears that the cam is shifted towards the cam cover by about 1/2 the width of the cam lobe. I have disassembled this engine so many times in the past week I can do it in my sleep. The only thing rough I felt is on the cam follower on the intake side. So I took some OOOO steel wool and tried to polish the cam follower. Then as I was reinstalling the cam follower I noticed that there wasn't much of the cam visible thru the tube. My thought was/is/are 1)Is this the correct cam for the engine? 2)Could the apparent misalignment cause a torqueing of the cam follower causing abnormal wear either to cam follower or the cam follower tube? Just thought of a third 3) Are there shims I'm missing to move the cam deeper into the cam housing?

The engine is really a jewel except for the LOUD snap as the intake valve closes. I have had 3 other OS 120 FS none had this noise. I really would rather figure this out than return the engine to the seller.

Again thanks, I hope that my description is a little clearer this time.

Mark
Old 06-23-2015, 08:09 AM
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When the cam is installed in the engine and the cam cover in place and tightened-down, the cam followers will ride on the cam. They will also slightly rub on the side of the cam gear, which turns them and evens-out any wear.

The noise you're hearing is most likely the lifter falling off of the cam as it rotates through. The cams have very steep lobes, so it's natural than some noise will be present when the cams move the lifters up and down. The presence of oil will act as a cushion and moderate the noise. You'll also get some noise as the lifter falls because the pushrod will bounce off the lifter, the rocker arm off the pushrod, and the rocker off the cam. Oil in all those places will temper the noise, but won't eliminate it. Some noise will always be present to one degree or another.
Old 08-02-2015, 04:37 PM
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Mystery solved! The motor had an incorrect cam cover. The cam cover on the engine was too short and let the cam wobble. With the correct cam cover smooth as silk.

Mark

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