70 350/350 rebuild

[Dean]

A friend of mine is rebuilding his 350/350 70 vette engine. when he goes to torque down the harmonic balancer, (65ft#) the pulleys and balancer are pulled in real close to the engine block (at 40 ft#)so that the bottom pulley is in too far the line up with the alternator pulley. What is wrong?, Why isn't he getting the 65ft# and the pulley's lining up? Why is the balancer being pushed in so far? Thanks in advance. Dean ncrs # 33,398

[wally]

Re: 70 350/350 rebuild

The harmonic balancer slides on the nose of the crank until it contacts the lower gear of the timing chain. The older vettes, late 50's had a 1/8 spacer behind the harmonic balancer to space it out, without it it had the same problem. I don't think the 70 motor used such an arangement. Could it be a different lower gear from the timing chain set? Also if the water pump was replaced, the fan/pulley mount does not always make it back in the correct position, but you said the altenator was not lining up?

[Joe L.]

Re: 70 350/350 rebuild

Wally and Dean-----

Yes, the 1970 350/350 (or any other 350, for that matter) does NOT use a spacer. The harmonic balancer installation depth is controlled by the crankshaft timing sprocket. I would suspect that it's highly likely that an incorrect sprocket has been installed or the crankshaft is damaged in such manner that the sprocket is installed to far. The latter is unlikely, though, without causing mis-alignment of the timing chain installation.

A Cloyes True Roller timing chain set (Cloyes #9-3100)will work perfectly and is the set I always recommend. If you install this set and have the same problem, you have some other problem. Make sure that you are using the correct balancer if you have replaced it. The correct GM balancer is currently GM #12555879. This is an 8" diameter balancer of 1-11/16" thickness.

If you wish to use a stock GM timing set, which absolutely assures dimensional correctness at the expense of durability, you require crankshaft sprocket GM #10128346, camshaft sprocket GM #340235, and timing chain GM #14087014. Also be aware that the pre-67 timing sets and sprockets are DIFFERENT. I don't know if it's possible to even install these on a 67+ engine, but if it is, that could be the problem if you were supplied with a pre-67 small block timing set by mistake.