Will a 400 SBC except a weighted 6 speed flywheel. The 400 is internally balanced I thought. So would the 6 speed flywheel need to be nuetral balanced.

 

all stock 400s are externally balanced, all other SBC motors are internally balanced.

 

You have to buy a special flywheel for the 400. I got mine from centerforce.

 

How much did that flywheel cost from Centerforce. Just curious what the difference is between the Centerforce and the stock T56.

 

It was like 350 bucks. You need it for two reasons. You have a two peice rear main and it has to be externaly balanced. The stock lt1 flywheel wont even bolt up.

 

Hey thanks for your help. Did you mean that the 406 is a 1 piece rear main and the T56 flywheel is for the two piece rear main.

 

406 has a 2-piece rear main seal. T-56 (LT1 engine) have a 1-piece rear main seal. Have to have a flywheel specially designed for that swap. I installed an aluminuim flywheel from fidanaza. If engine is stock (externally balanced) you will need a balance plate to use the aluminuim flywheel I used. Centerforce steel fylwheel is balance already for externally balanced engine (383 400)

 

The car was an automatic before and I didn't see any weights on the stock flywheel. We did not build this motor, but it has been rebuilt. So I'm not sure if it was nuetral balanced or not. I would this it would have weight on the flywheel if it was externally balanced. The crankshaft does have a different bolt pattern than the t-56 flywheel though right?

 

yes it does cause its a two peice rear main where as an lt1 is a one peice rear main

 

You can internally balance a 400 block and use a regular 350 balancer - it costs more to do, but is much better for high perfomance use.