Balance issue… help!

[olddog]

If it did indeed dyno smooth, then the ballance had to be right at that time. The ballance does not change. The only thing that could have changed is the harmonic ballancer on the front and the flexplate/flywheel on the back. For high performance purposes, most say you should have the engine ballanced, with the parts you are going to use when the engine is installed.

I think you said, from the pictures, the harmonic ballancer is the one that was used during the dyno work. That only leaves the flexplate. Did it get changed?

I'm more of a book worm than actual engine experiance. I have built a few engines, most a long time ago. I have been around some racing stuff and know people in many different types of racing. So be ware that I am not an expert. Ususally my troubleshooting instincts are good, but some times I am dead wrong.

With that said, it is my belief that the damper and flexplate for a 28 oz off set has some spec on where and how much it is supposed to be off ballance. I do not know what that spec is, but many people do. I have never heard of anyone adding to or taking from the ballance on those parts. I'm sure there is slight variation from part to part. It would make sense to me that someone might make a slight change to get these part dead on, if they were at the far side of the spec, but I never heard of anyone doing it. That is why they say ballance the engine with the part you are going to run.

The slight variance in ballance from one damper or flexplate to the next might make the differance in an all out race engines life span, but it is not going to be felt. So if you have the correct parts on the engine that it was ballanced for, you will not feel any vibration.

This brings me back to what changed. It is possible to cross two plug wires and the engine not backfire. This will cause a noticable vibration. A dead cylinder from a bad plug or wire will cause a vibration. That is why I question if the engine is running correctly. The more radical the cam the less noticable a dead cylinder.

If that didn't answer your questions fire them back at me and I'll try to answer them one at a time. There are lots of guys on this forrum that are masters in this trade. They may chime in. If I tell you wrong, I think someone will correct me (hope so).