I had my motor rebuilt. I went ahead did the 383 with the LE3 h/c. Car feels very strong. But i am getting heavy vibration as my rpms go from 3k and higher. I did use the search and it maybe that my motor was not balanced correctly. If that is the case what would need to be done to resolve this vibration? Would I need to get it rebuilt again?...Just trying to get an idea of how much im going to have to spend again to get it fixed.

 

Same vibration over 3k and it ended up being my drive shaft. Something you might want to check.

 

could be a ds, dampener, balance, etc

 

Break it down a little more first. Does it vibrate in neutral revving the engine? Does it vibrate while moving in gear or just while moving in neutral? If you feel it while coasting in neutral or while coasting at any speed, its not the Driveshaft (most likely). What type of balancing did they do? If they internally balanced the motor, your flexplate should not have a "batman" weight on it, if the motor was externally balanced you will NEED that "batman" weight on the flexplate. I had to get one that had the weight and my vibration has since gone away. Hope that helps.

 

Flywheel type and brand...engine balance internal or external? i had external balance flywheel on internal balanced engine...no go. Had to pop the weight off...

 

Yes it does vibrate when im neutral and rev it. I start to the feel the vibration around 3k rpm and up. It is an m6 so it does not have the flex plate. It has the stock flywheel. So what do you think im going to have done? balanced again? Would i have to pull my motor out to get it blanced?

Thanks for all the help.

 

If the motor is internally-balanced, you need a neutral flywheel.
If you are running a stocker, it will vibrate.
If you run it like that long enough, you'll turn your new motor into an expensive doorstop.

Check with your engine builder, they should have documented the balance and any external requirements.

If no combination of availabe flywheels work and you can't find the necessary documentation, it may have to
come apart. It's possible that the mains were mis-installed, rod bolts were not tightened properly or that the crank itself is cracked.

I just went though this with a 355 that was suposed to be internally balanced.
Turns out that not only was it out of balance, it was cracked, someone had put the mains on backwards
and in the wrong order then didn't tighten the rods down properly. A very expensive repair.
Good thing we didn't try to dyno tune that thing ... it would have ruined a lot more.

 

I think we figured out what the cause of the vibration was. When the rotating assembly was balanced at the machine shop they used a flex plate. I have an m6. So now they are going to match balance the flex plate to the flywheel now. I hope this fixes the issue and my motor is not damaged with the driving I did while it had the vibration. I should have an update by this friday.