Does my motor need rebalancing?

Hey guys, I am a little confused about something. I have a forged 357 ci in a 95 z28. When we started the car, it had an AWFUL vibration! We took the motor back out and had it rebalanced. When it was balanced they used a stock crank pulley. I have since ordered a t-trim. Do I need to have it rebalanced w/ the pulley that comes w/ the t-trim? They had to take a little weight off of the stock pulley to get it in balance. The shop where the car is says I need to have it rebalanced again w/ the pulley from vortech. If I dont need this I dont want to do it but If it needs to be done, i need to go ahead and do it while the motor is apart. What do you guys think?
Thanks
Scott

Get your new balancer balanced to match the one you are taking off. I think most competent machine shops shouldn't have a problem doing that.

Have any idea what that would cost?
Thanks
Scott

Did it always vibrate? My IROC vibrated after rebuild, it turned out to be a cracked flex plate, I thought it was cuz I didnt have the rotating assembly balanced.

Originally posted by BOOST FED 95Z
Have any idea what that would cost?
Thanks
Scott

Scott, hey man this is Stephen, I guess you are posting at work. If ya can could you PLEASE call me at 345-4084, it's important. Thanks man.

quick ?-

internally or externally balanced



and are your vibrations speed or rpm specific?

Thanks for the responses, As soon as we started the car it vibrated, and this was a vibration that you just couldnt stand to sit in the car....I did it at idle all they through the rpm band, didnt matter what rpm or what speed. When we pulled it back apart we also found out that once cylinder had not fired at all, I needed longer pushrods, and the cam that I had installed wasnt the cam it was supposed to have been. I dont know how much of which of these problems helped w/ the vibration but all I know is it was unbearable.

Stephen, I will call you after 7.
Scott

Originally posted by BOOST FED 95Z
Thanks for the responses, As soon as we started the car it vibrated, and this was a vibration that you just couldnt stand to sit in the car....I did it at idle all they through the rpm band, didnt matter what rpm or what speed. When we pulled it back apart we also found out that once cylinder had not fired at all, I needed longer pushrods, and the cam that I had installed wasnt the cam it was supposed to have been. I dont know how much of which of these problems helped w/ the vibration but all I know is it was unbearable.

Stephen, I will call you after 7.
Scott
thanks, that answers a question i've had for a while-

i thought my engine might not have been balanced right when i had vibrations but i think its my driveshaft-

thnx again

but the driveshaft only spins when the car is in motion, i thought it was a permanent vibration? if its the motor, goin in neutral will make it worse.

Trey, yes my vibration is permanent, no matter what gear rolling or not. I hope that it was the motor needing balanced. If it is not I dont know what else to do.
Thanks
Scott

Originally posted by Nitromethane
but the driveshaft only spins when the car is in motion, i thought it was a permanent vibration? if its the motor, goin in neutral will make it worse.

my motor shakes my whole car:bow:

any else have any opinions on this? If I get the machine shop to measure the drills on my stock pulley and have them make the same drills to the vortech pulley...will this work?
thanks
Scott

Just bought a flywheel for your motor.. I think its internally balanced, which then it wouldnt work with the flywheel because its offset about 16oz to "externally" balance the stock motor because the stock motor is externally balanced, if you have the motor internally balanced that would cause a vibration if you used the stock flywheel.. vortechs pulleys should be neutral balanced, anymore weight would cause a vibration too.. I hope you know if its internally balanced or not.. If its externally balanced I just wasted 300 on a flywheel, i had it neutral balanced... lol..

An LT-1 is half/half.The front is "0" balanced internal,the back half is external balanced with a weight on the flexplate/flywheel.Don't know how it was balanced but the balancer,flexplate and internal's that you are going to run should have been balanced together, however it was balanced internal/external/or half and half.Adding a pulley will not effect the balance if it was done right to start with.If any of the balanced item's were changed after balancing,that would be a good place to look for your vibration.

This is what got my attention: "I needed longer pushrods".

If someone assembled this motor without checking the pushrod lenght, then I would pull the entire assembly down again, find another machine shop and or engine builder and start all over.

Just my $.02

Jim