Alright I have almost everything I need to swap my new motor in my car and I ran into a little problem. The engine in the car is a late model engine , and the new engine is a 70's model engine so I need a different flexplate right? I am almost sure i do need a new one, but what flexplate do I get, what piece rear main seal, how many teeth, etc. Also if anyone has done this swap and knows of a car that had the specific flexplate I need so that I can pick it up from autozone please let me know. I appreciate the help.

 

get one to fit the engine. tell them what year and what car it came from.

 

if original engine is 86 and up then yes you wil need 85 and older plate, if you need oen then i have one for cheap

good luck

 

wouldnt I need one for a 2 piece rear seal, and 153 teeth. Or am I wrong on that . I am sure I need a 153 tooth flexplate for the stock starter, but can I get one for a 2 piece rear seal aswell. Fast68, what year engine did that flexplate come off of? I would buy it if I knew it was the one i needed.

 

You need a 168 tooth flexplate for a two-piece rear main seal motor. The 700R4 uses the big flexplate (168) and the motor is a two-piece rear main. They are easy to find. I probably have two laying around.

 

I'll have to disagree with that. The TH700-R4 in 3rd-gens uses a 12-3/4", 153 tooth flexplate. The application you need is '83-'85 F-body V8 automatic. That will allow you to retain the orginal 3rd-gen starter.

 

Does your year engine require a internally or externally balanced flex plate? This is critical. Either way it will be be a 168 tooth.

 

Well I beg to differ, because the flexplate that came off my '86 was a 168 tooth for a 2-piece rear main seal. I had to buy a starter for it at one point, and it was the staggered bolt pattern right from the parts counter, so it isn't like I had parts on the car that weren't factory.

If there's any doubt just measure the one that came off the car. If it's 12-3/4" its a 153, and if it's 14" then it's a 168.

 

The 168 tooth is also on the 1 pc oil pan gasket. Externally balanced

 

It wasn't factory, then, because '86 was 1-piece rear-main and 153-tooth.

Agreed.

 

Live and learn.

 

No, the engine isn't factory. Someone had installed a crate 350 before I bought the car. When I bought the new starter for the car I told the parts counter guy that I had a TPI 305 with an automatic, and he gave me a starter for a 168 tooth flywheel, which matched what was on the car, so to me this car must have come from the factory with the 168 tooth flexplate. Maybe GM used different flexplates on different motors. They've been known to do wierd stuff like that.

Anyway, measure it to be sure.

 

are we still debating the tooth count?

 

No, I think we finally reached "measure it to be sure".