Hey guys,

I have bought a pontiac 400 with a borg warner super t-10 4 speed.  the flywheel is missing.  I have found a few on ebay-a couple of used ones and a couple of new or refurbished ones.....the latter ones are "internal balanced".  I have no idea what the difference is between internal and external balanced flywheels is....I assume the safe bet would be top buy the used flywheel, but it does not specify if it is internal or externally balanced.....any thoughts greatly appreciated.  Thanks, Duane.  

Hi Duane, I've read this post as well as your other post about engine balance. The one thing I can add is that in addition to being an internally balanced design, meaning that the flywheel (or flexplate) and harmonic balancer are neutral balance (no offset weight- may still have small weights to bring the part to neutral balance), there was achange in the rear flange of the crankshaft after 75, so a 76-79 motor needs a 76-79 flywheel or flexplate, 75 and earlier require the early parts. Best bet is to e-mail the seller and see what he says the original year and engine the flywheel is for, don't let on what you have or the seller will likely tell you it fits (even if it doesn't).  

As Barney stated the large center bore of the flywheel changed . If you buy used or new make sure what size you need then ask what size they are selling and year as suggested. I would buy  a new aftermarket one because they are usually drilled for the large and small pressure plate bolt pattern ( HAYS ). I have seen more than one Pontiac with an ugly wide hole in it from an exploding clutch.Not my idea of a hood scoop.
 If you are really going to run it hard and are not an ORIGINAL ONLY guy I also suggest a steel lakewood bellhousing. Used would be OK in my humble opinion.

           Good Luck,  Eddie