Quote:
Originally Posted by lust4speed
And expounding on that, if the engine required a line bore when rebuilt it wasn't because Pontiac got the mains out of line, it's because the block twisted and curved slightly over the years from the heat cycles. This curvature is throughout the entire block including the cam tunnel. If the cam bearings weren't clearance when the new cam was installed and went in tight, it is going to make room for itself. Unlike removing a thousandths or so of material with a knife or homemade cam cutting tool, the cam will generate heat on the Babbitt until the material gets hot enough to move around out of the way. Enough binding and the Babbitt smears over and covers the oil hole. Then the Babbitt gets hot enough to drip out of the shell. If a lip is created then it is difficult to remove the cam without knocking the bearing loose. Even a little generated heat can be enough to delaminate a layer of Babbitt and there will be flaky holes visible.
Anyway, a good look at the bearings will tell you whether you were just a little out of line pulling the cam or if you have problems that need to be addressed before putting in the new cam. The new cam needs to turn with minimal resistance or it will have problems later on.
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X 2, Mick. This is WHY I always check cam bore alignment. Just because a block is made of cast iron does NOT mean it doesn’t distort over time.