340 Static Compression Numbers and Test Procedure

Let's not confuse functions..... The elastomer and inertia ring in the damper is not for primary balance anyway; it is for torsional vibrations (i.e., very high rate twisting vibrations) inside the crank. The 'shake' question is related to primary crankshaft balance and whether the damper/balancer needs any external weight on it, or not.

But, if the damper mark is off 50 degrees like the OP sez, and not the 90 degrees + or - CCW like the older style damper, then something is quite wrong with the inertia ring position and the damper. So it ought to be changed out. And ditto for the cracks in the elastomer as said.

From imbalance reports here on this forum I can believe some pretty high bobweight mismatches (which I am sure is what YR is referring to) and not have it be felt. Does not mean it is good inside the motor. Just says we still don't know about the engine balance here.