zodiacblueS

This is my first rebuild. Is the timing chain cover the only thing that holds the cam in? When I pulled the cover off there was a slight wear mark where the cam bolt was rubbing. No indent, but it seems there should be a bushing on the cam bolt end? If thats the way it's designed, its fine with me. I know the roller chain and balancer and water pump should cinch it in, but am I missing something?? Thanks for your time.

Oldsmaniac

The end of the bolt acts like a bushing....the chain and gears keeps it from walking too much. On disassembly the lifter will not let the cam slide out so they need to be removed for that.

Oldsmaniac

The distributer gear also helps lock the cam down....

zodiacblueS

Thank you Maniac. I'll have more questions tomorrow.

joe_padavano

Not "helps", the helical angle and rotation direction of the distributor gear ABSOLUTELY pulls the cam back into the block. That's why there's a flange on the end of the cam that rides on the front face of the block. There is some "bounce" in the gears that lets the cam bounce back and forth, thus the wear marks, but the predominant load is backwards.

Oldsmaniac

Thank you for firming that up.

zodiacblueS

Thank you gentlemen.

rsandhoff

I'm certainly no expert and I have only built one OLDS engine ( 69 400) but here is what I found. The stock cam bolt has a protruded head, slightly smaller and round, from the area where the wrench goes. This protruded area is what hits the timing cover slightly and keeps the cam from moving back and forth very much. As stated earlier, the basic design pulls the cam backward. I am adding to this post because there is a different cam bolt that has a thrust button built into it in the area that hits the timing cover. I'm not saying these are better, just another option. The thrust button acts as a buffer between the cam and the cover. It also spins on the end of the bolt itself. Mondello and others sell this bolt.