Diagnosing Engine Whirr

1930 said

Id like to know/have an easy to understand definitive test to say either way that the slop is just too much if you come up with something.

I have a couple of spare engines I am playing with and I would like to test them.

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I just followed Bill's suggestion of grabbing the crank pulley and rotating it back and forth while watching the distributor rotor button for movement. It took 5-6 degrees of crank movement (read off the crank timing indicator) to take up the slack in the chain and make the rotor buttom move. Attributing all of the crank-to-rotor-button slack to the timing chain assumes that the distributor gear is pretty tight on the cam, but in my case, I could easily move the crank pulley back and forth at least 5 degrees. 5 degrees is a LOT of timing slack and the calcs above show that 5-6 degrees chain slack at the crank corresponds pretty close to the '62 FSM service limit. (That seems like a pretty sloppy service limit.....)

BTW, that actual FSM check is to block the crank for no movement with the timing cover off, and rotate the cam gear back and forth to see how much a chain link on the cam gear on the side of the gear opposite to the crank gear will move. That movement should be under 11/64".

I don't have any info on how much/little movement there is with a new chain. I'll be finding out.