Hi all, is there a definitive answer to which Flexplate I would have with regard to the amount of teeth the ring gear would have in my 1983 5.0 CFI Trans Am with a 700r4? I know I can pull the bottom cover and count them by hand but thought if its a definate one or the other it would save me crawling under until I need to.

I'll be popping in a 383 one peice rms block so i know i'll need a weighted 1 piece rms flexplate and 400 front dampener but i'd like to get the flexplate before I pull the 5.0.

Thanks all.

 

Assuming it's original, it'll definitely (the word has no "a" in it; spelled just like "definitive") be the 12.8" (153 tooth) one.

Make sure you know what balance your 383 crank needs. Some take the stock 305/350 balance, some need the 400 balance. Which of course the 400 never came with either a 12.8" wheel or 1-pc RMS. It'll be a "special" if it needs that. A "pork chop" weight might also be an option if you need the non-stock setup.

 

I had to go through this mess with my 334 (stroked 305) which happens to be external/external balanced.
While you can easily get a counterweighted harmonic balancer, finding a properly counter-weighted flexplate balanced to your engine can be difficult.
I suggest (if you have the option) that you get your 383 fully INTERNALLY balanced. That way if you have to change the balancer or flexplate down the road, you can avoid the problem of trying to find one that will match. For my 334, I had to get a 153 tooth SFI flexplate and add a counterbalance plate.