Cam thrust bearing spins

[Mike M]

I'm rebuilding a 140hp, and found out after assembling most of the block, that the cam thrust disk is not supposed to spin on the cam. Mine does. Is this a problem that is big enough to warrant tearing the engine back down, or not?

[davemotohead]

That is a subject of debate, does it just spin or is there side to side movement? I have seen them both ways on factory GM installed cams, ideally you want it pinched tight between the gear and the cam when the gear is installed, but think after a while they loosen up and spin, I just checked 6 GM cams in my garage and 3 of them spin 2 don't and one moves but is tight, Did you use the old cam and gear or was this a new cam and gear?

[Mike M]

It is a reverse rotation engine that was in a Sterling kit car, running well. The thrust disk turned free, but didn't seem to have side play.

[66vairguy]

It is a reverse rotation engine that was in a Sterling kit car, running well. The thrust disk turned free, but didn't seem to have side play.

I have observed the same thing as Dave has with factory cams. Spin is fine as long as there is no end play.

[Mike M]

I'm thinking of maybe checking end play on the cam?? Is there a spec on that?

[Mike M]

Thanks 66vairguy! Didn't see your post until after I sent that about checking end play. I think I'll just declare it a non problem, thanks to Dave and you :-) we'll continue with the build and hope for the best.

[Dennis66]

Cam thrust washer spinning: Well everyone knows that all depends on what oil you choose to use. Dennis

[66vairguy]

I'm thinking of maybe checking end play on the cam?? Is there a spec on that?

I've only seen an endplay spec for the crankshaft, none for the camshaft. Since the cam gear pushes the cam in one direction the thrust washer is always pushed against the block surface. Of course in a revers rotation engine the cam gear force is reversed (unless the cam gear and crankshaft gear teeth angle was reversed).

I've never heard of anyone having a cam shaft issue with a reverse rotation Corvair engine.

I assume you know you have to reverse the piston orientation for the offset wrist pin piston hole on a reverse rotation engine.

[Richard]

1965 manual, pg 6-33, #7 reads .002" to .007" endplay, shown in Fig. 61.
As long as endplay is within specs, it doesn't matter if washer is loose.

Chevy inline six and tall block 366 & 427 truck engines call for .005" max and .004" gear runout. They also use cam gears and no chains.

I should add that if gear is installed incorrectly and gear is galled, runout will be .020" or more.

[66vairguy]

Thanks Richard for posting that --- it goes in my notes.