Topic: internal balanced / external balanced / unblanced OH MY????????????

[YellowJacket]

So confused. I own a 76 T/A. Has a "reman" W72 78 400. I need to replace the flywheel, pressure plate and clutch. So, the 400 engine is internally balanced... so far as I am aware. My 400 crank register is 2.49". Now the Centerforce Flywheel 700610 is for an externally balanced motor. The 700600 by Centerforce is counter-balanced. Can anyone help with which one I need?

[LilSki]

This is a confusing subject that even I haven't got my head wrapped fully around. But I believe stock pontiacs have a slight 4.22oz inbalance built into the flywheel. The problem is when these engines are rebuilt they are often fully internal balanced so a Neutral balance flywheel is required. Unfortunately there is no real way to tell unless you maybe take you current flywheel to a shop why can tell if it has the 4.22oz inblanace in it. You can't always go by the old flywheel part number, if there is one, as it could have been converted to neutral balance.

If it was just a simple reman W72 my bet is you need the 4.22oz inbalance flywheel. 

[YellowJacket]

Thanks LilSki. I took flywheel to a local machine shop who has re-surfaced many flywheels. The gentleman said that all flywheels get cracks from the constant heat/cool cycles, and that mine wasn't that bad. He charged $25 to re-grind mine and sent me on my way saying that this flywheel had never been re-surfaced and that it will be fine. So, that saved me alot of money and so I splurged for a Centerforce dual-friction clutch and PP. Next I need to replace the rear-main seal using an expensive $80 Viton that they claim will not leak like the rope. Then I will paint the motor and drop it back in. Can't wait. To the point of discussion, I have it on good authority that Pontiac 400's are internally balanced. But boy what alot of back and forth and confusion there is on this subject on the web.