1972 base 350 harmonic bal issues

[Stephen B.]

Replacing the harmonic bal on a 72 base 350. Recieved a new fron a vender and base timing mark was at least 20 to 25 degrees advance fro 8 degrees int from orginal dampner, The engine is good with base at 8 and cam set. was running okay, Repace just because of age. Anyone had this issue? Thankyou

[James G.]

The timing mark should be slightly counter clockwise from the keyway slot - iirc on an 8" balancer it's about 1/2 " counter clockwise from the key way - if you projected both out from the center of the crankshaft mounting hub.
Does that make sense?
I have a brand new 8" GM balancer which is 1.25" thick I checked.
IMG_20250919_203849[1].jpg
If the tdc mark is different than this the ring could have slipped on the original balancer.

[Joe L.]

Replacing the harmonic bal on a 72 base 350. Recieved a new fron a vender and base timing mark was at least 20 to 25 degrees advance fro 8 degrees int from orginal dampner, The engine is good with base at 8 and cam set. was running okay, Repace just because of age. Anyone had this issue? Thankyou

Stephen------


I think you have a defective balancer. The original balancer for your application is a 6-3/4" balancer of GM #6272221. That balancer was discontinued and is currently replaced by GM #12551537. If I was you, that's the balancer I'd want to use.