28 oz inbalance, or not??
 

I have a '72 with a 302/FMX combo (seems to be a rare combo). Does anyone know the inbalance of the flex plate?? I properbly have a flex plate of a 351 engine (because my engine vibrates), but to be sure I have to know if there is a difference in inbalance between these two. If there isn't than that can't be the problem!

If you are sure it is a 72 then it is 28oz just like the 351. So that is not the problem. How does you harmonic balancer look?

I've already replaced the balancer, so that is not the problem...
But your sure that if I replace 302/FMX flex plate for a 351/FMX flex plate it's the same?

Yes as long as you are sure you have an early model motor someone correct me if I am wrong on the year but the 302 did not become 50oz imbalance until 84(it was in the mid 80's, I think the exact year was 84). Up until them all small blocks were 28oz with the exception of a very few that were neutral balanced such as the Hi-po 289's.

Rule of thumb. Gray block, 50oz. 1982 & up.