Quote:
Originally Posted by Slick
Another source of mystery heat in rebuilt engines is tight cam bearings. Frequently in 70's blocks I'd find that after having cam bearings replaced, the cam couldn't be turned in the block by hand (no valve train in of course). "Machinists" always seemed to want to grind away some cam bearing material with a knife.I wonder if either of these two (and maybe other) machining issues could be contributing to excess heat production by the typical rebuilt Pontiac engine?
Stuart
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I had the exact same problem after installing new cam bearings and cam in my 68 400. It would alternately turn ok a few degrees and then tighten up considerably. The machine also suggested scraping the cam bearings. Using a magic marker, I coated the bearings to see where the interference was. But after several trys, it wasn't helping and the bearings wear looking like hell. I couldn'e see how this hand-"machining" was worth a darn!
So, I chucked the cam up to a lathe and discovered the cam was bent about .006"! The bearing clearance is only .002", so it was obvious that the cam was gonna wear the hell out of the bearings when the engine was started.
They got me a new cam and bearings and everything turns smoothly now.