Hello everyone.
Recently got my car out of storage and working on it again after a long layoff.
Before I put it in storage I swapped in a t-56 out of a 95 tran am ( lt-1) engine is 350
Crate motor with one piece rear main seal. T-56 was rebuilt and I used new clutch and flywheel vehicle specific to the trans am. It has a very noticeable vibration and it just doesn't run correctly. Should I have had the flywheel balanced? I can feel the vibration on the floor directly in front of the drivers seat. Most of what I have read is about mating the t-56 is to a two piece rear main seal so I'm unsure how to pursue this issue. Any ideas would be greatly appreciated.

Thanks

Need to have the flywheel balanced the same as the flex plate that was on the engine.

Was your engine internally or externally balanced when it was built? Did the flywheel that came off the engine have external balancing weights on it or not? Did the flywheel you installed have external mounted weights on it or is it zero balanced?

I remember the flywheel had no weights at all. The flexplate is long gone and I don't remember if it had any weights. I think I should have balanced the flywheel and flexplate together but hind sight is always 20/20. Guess i am up the creek with out a paddle now!! Have no idea if the engine was externally or internally balanced. It's been in the car for about seven years now.

Stock lt1's are externally balanced iirc. You should just have to take the flywheel to a machine shop and have it neutral balanced.

I thought since it had no weights that it was neutrally balanced. The engine is one piece rear main seal so it's 86 up block but not an lt-1. The thought of taking the transmission out all over again is not pleasant but I'm getting this right whatever it takes. Thanks everyone....

Hmmmmm......
This definitely has me interested in what someone comes up with since I have always been under the impression that the stock LT1 flywheel would bolt right up/work just fine with an 86 and up 1 piece RMS gen 1 sbc

I thought this was a simple bolt in as well since the expensive 2 piece rear main seal flywheel wasn't going to be needed. I'm thinking that I should have had the flywheel balanced so I suppose I could remove the flywheel and have it balanced but I want to solve the problem correctly. I would prefer a bolt in solution specific to this application but at this point I'm still debating how to pursue this issue. I accept that modifying the car will create these problems.

The flywheel does bolt up no problem, but some engines are internally balanced, and some externally balanced.

My 383 is internally balanced, so I had my stock lt1 flywheel neutral balanced.

So then the lt-1 flywheel I used that had no weights on it was not neutral balance as I thought? After countless hours in this the consensus is that most 1 piece rear main seal if not all are internally balanced but I have to continue the investigation. My next step to contact a few aftermarket flywheel dealers and get their information on this. I hope my situation alerts others as to avoid my mistakes.

Good luck all

I don't think they used weights on the flywheels, just drilled holes to lighten up parts to match. It sounds like you need to have the flywheel neutral balanced. What crate engine did you buy?

340 h.p. 350 crate engine from eBay vendor Phoenix musclecar. Crank is one piece rear main seal so I know the block is 86 up.

Can you ask them what there engines typically are balanced?

I'm contacting the company to get that information. Depending on what they tell me I will decide what course of action I'm gonna take. Maybe replace the flywheel with aftermarket or simply balancing the flywheel I have now. Need more information before moving forward though.

Thanks again

As per the engine company my crate motor was internally balanced. I'm gonna have the the factory flywheel neutral balanced.

Good deal!