T-56 flywheel

[MarkM66]

I've always read that a stock T56 flywheel from a sbc with a one piece rear main seal, will not work on an a pre '86 engine with a two piece rear main seal.

Anyone know why this is?

[Mkelcy]

Different bolt pattern. The issue isn't the T56, it's the one piece versus two piece rear main seal design of the crankshaft.

[MarkM66]

Are all 6 bolt holes different? Thanks

[Mkelcy]

Are all 6 bolt holes different? Thanks

What are you trying to do?

[Samckitt]

Bolt circle diameter is different. 3.0" for 1 piece seal compared to 3.58" of the 2 piece.

Found this:
SOLVING THE BOLT PATTERN PUZZLE
GM engineers redesigned the crankshafts used in production small-block V8 and V6/90-degree engines in 1986 to use a leak-resistant one-piece rear seal. This change from a two-piece to a one-piece seal required a change in the bolt pattern on the crankshaft flywheel flange. The bolt circle on pre-1986 production crankshafts is 3.58" in diameter. 1986 and later cranks have a 3.00" bolt circle. In addition, all cranks which use a one-piece seal require a counterweighted flywheel for proper engine balance.

[Morgan]

Depending on your setup and what T56 you are using you can have clutch fork / flywheel clearance issues as well. I had to have McLoeod make me a flywheel as all the aftermarkets out there were too thick.

[Jim H]

2 piece Gm crank is internally balance where the 1 pc version is externally balance. If it were to bolt up, you would be looking for trouble.

[796spdbu]

How much does it cost for the custom made mcleod flywheel?

[Morgan]

When they made my flywheel they charged me the normal price for a T56 flywheel, I think it was around $400. They also said that they would be putting the one made for me into regular production. I would contact them directly and I can get you the specs from my flywheel if you need them. Please keep me posted on your progress, I would like to know if someone else benefited from my discovery.

[andrewb70]

Not only is the bolt pattern different, but also the size of the center register is different. The bolts do not center a flywheel on the crank.

Andrew

[MarkM66]

Great information. Thanks.

So only the aftermarket makes a flywheel that'll mate a T56 to a two piece rear main. Right?

[Morgan]

As far as I know.

[andrewb70]

Great information. Thanks.

So only the aftermarket makes a flywheel that'll mate a T56 to a two piece rear main. Right?

I believe that is correct. No such GM part exists. The T56 didn't exist when two piece rear main engines were being produced.

Andrew

[1Bad68camaro]

Did you ever find out about that flywheel being made? How much is it now? And where is the best place to buy it? Thanks

[andrewb70]

Did you ever find out about that flywheel being made? How much is it now? And where is the best place to buy it? Thanks

Check McLeod, SPEC, Ram. I bet they all offer a billet steel flywheel for this application.

Andrew

[SuperSport623]

LT1 T56 mated to a pre-86 SBC.. this is the flywheel you need, i believe.. im looking into buying it


http://store.summitracing.com/partde...5&autoview=sku

[oldrednova]

LT1 T56 mated to a pre-86 SBC.. this is the flywheel you need, i believe.. im looking into buying it


http://store.summitracing.com/partde...5&autoview=sku

This is the flywheel I used for my swap. It works great, but your going to need a ministarter with no nose cone, like the Powermaster's, in a stock LT1 bellhousings.

[TD509EFI]

THis is the one you need if your using an internal balance two piece seal small or big block:

http://store.summitracing.com/partde...7&autoview=sku