Well i called up my local machine shop and asked them if they can balance my new Street Twin flywheel to the old one. He said it’s not possible to balance the flywheel, since the LT1 is externally balanced. BTW why DO WE HAVE TO BLANCE THE STREET TWIN FLYWHEEL? I put my friend’s street twin in, and we just slapped everything on, and had 0 problems with vibrations etc.

SO how are u suppose to balance the flywheel without bringing the whole engine there He said its the only way to do it right.


Thanks
Marcin

 

>I had my machine shop zero balance my SPEC fly wheel by it self (on this lathe looking machine) and since they are the ones who built my shortblock then they knew it was already balanced .

 

well that really doesnt answear my question....
Thanks
Marcin

 

I haven't had to do this yet, but have done a lot of reading on this board about it.
As far as your friends flywheel being ok with no vibrations, i think is more of a luck thing than anything else. Sometimes the aftermarket flywheels work correctly, and sometimes they don't. Me personally, i would get it balanced to your original flywheel.
I am getting ready to do my T56 swap, so at first i am going with a stock flywheel, since i don't have an existing one to balance from.
And since the LT1 engines are EXTERNALLY balanced, the new flywheel needs to be balanced to the old one. I'm sure if you looked at yours or your friends original flywheel it is weighted somewhere. This is where the externally balancing comes in to play.
The machine shop was correct in a way. The Absolute Best way to balance the new flywheel is by taking the engine in and balancing the flywheel from that. But, since that isn't an option for most people, the new flywheel can be balanced from the old one and work just as good. My .02

 

>I should have also said that SPEC offered this balanced , but the machine shop still had to zero balance it .

 

oh well..there is no weights on my flywheel..i guess ill be taking a chance and bolting everything straight up. If it doesnt work no biggie, just drop the tranny again
thanks
Marcin

 

Externally balanced = weight on the flywheel. If there isn't a weight bolted to the flywheel I wouldn't put it in.

Its not my car, so go for it and let us know what happens .

Ryan

 

I just finished swapping the M6 into my car ( I LOVE THIS THING). The flywheel was what i was concerned about. Well, i get the flexplate off and compare it to the flywheel. The counterweights, to my delightful suprise, were at THE EXACT SAME POSITIONS ON EACH. I bolted it in and have no vibrations. I talked to an engine builder in florence before the swap and he said the the SBCs are externally balanced... but since they're as mass produced as they are all the bob weights are calculated to within a certain percentage error before assembly and all the engines recieve the same counterweights in the same positions. Even the Haynes and Chiltons manuals tell you to put the counterweights on the same position of a new flywheel/flexplate if you have to replace the old one.

 

http://bellsouthpwp.net/x/x/xxsaint69x/flywheel.jpg

here is what my stock flywheel looks like...i dont see any weights bolted in??

could someone post a pic of a street twin flywheel?

 

http://www.street-legal.cz28.com/catalog.html

not a street twin but a SPEC aluminum flywheel. It has weights on the back of it. I was told that the flywheel is going to be balanced from the factory on aftermarket flywheels such as SPEC or mcleod.