Have a 88 lx with a CHP 347 kit. I bought this kit used from a friend and was supplied with a 50 oz balancer and flywheel. I've driven the car for 2 years now without issue. What seemed like "normal" engine vibes. This past week I had some work done at a shop and the mech was telling me all 347 cranks are 28 oz balanced. From research I see they can be either. 50 oz cranks look like "Swiss cheese" per say. Mine in fact does look like Swiss cheese holes drilled. Would it be safe to say this crank is probably 50 oz imbalance? I have No numbers off the crank as it is installed. Any info would be great! I am at odds whether I should change out the flywheel.

 

This is a question for the guy you purchased the kit from, it could be balanced either way. CHP does in house balancing also for an extra cost. So ask your friend if when he ordered the kit if he had it balanced before it was sent out, or if he took it someplace to have it done. Obviously if he provided you with a 50oz balancer and fly wheel that is what he was using correct? CHP will do either 50oz or 28oz depending on what you want. They recommend having a 28oz imbalance, especially with and after market crank. This is supposed to save the integrity of the crank at high rpm.
If your counter weights are full of holes then it is most likely a 50oz imbalance.

As for the mechanic , he is wrong. Not all 347 engines are 28oz. Most places do it that way , and recommend 28oz to keep the crank from aerating the oil so much and to maintain crank integrity, but they can be and are done either way.