Hello, I had a 383 built for my 1991 Z28. Last night, I went to put the starter on (from the old motor), and it would not fit, the gear shaft on the starter hits the flexplate before the bolt holes line up. Luckily I had my old motor/tranny, a 305 bolted to a 700R4, and took a look to compare. My old motor has a flexplate smaller in diameter. The new flexplate barely fits in the new 700R4 bell housing, in my old bell housing, I have more than a finger width of room between the flexplate and bell housing. Is this the difference between a 168 and 153 tooth flexplate? Are both flex plates intended on fitting in the 700R4 bell housing, should I put my old flexplate on the new motor? I was thinking about a starter similar to the one in the link below if the larger flexplate is OK: http://www.summitracing.com/parts/SUM-829100/ Also, because the starter will shift to the right of the car, how do I get a lower torque converter cover that will accommodate the new starter location? Thanks, any suggestions are appreciated.

Yes, that's the difference however a 1 pc seal crank has a larger diameter flange & bolt circle than a 2pc type crank. The flexplates don't interchange.

Thanks Twin Turbo!

I would assume the 168 tooth flexplate is the larger diameter. Summit has the below two flexplates, both 168 tooth, one is for 1-piece, the other is for 2-piece.

http://www.summitracing.com/parts/CMB-08-0002/

http://www.summitracing.com/parts/CMB-08-0001/

You had just gave me a big scare because I just went through all sorts of garbage w/ the builder as far as if he went with 1 or 2 piece RMS.

Both my old and new blocks are 1-piece seals.

None the less, the info you provided was very helpfull to at least point me in the right direction! At least I know things seem to be OK again.

You definately need a 153 tooth flywheel far as i know all thirdgens ran a 153 tooth flexplate, 168 tooth flexpates were usually used on trucks.

Thanks Iroc-Z28Man!

Other than the added weight of the larger flexplate, and the new starter, is there anything else about the larger flexplate that would cause things not to work, or work incorrectly?

Even though the 168 flexplate barely fits in the bell housing, it does, and I am pretty sure 700R4s that were on GM trucks had the same size bell housing, I should be OK w/ the larger flywheel, right??

I'm sure the smaller, flexplate would save me a few HP at the wheels w/ less rotating mass, but at this point, I don't think 5 HP at the wheels is worth me dropping the tranny AGAIN. Yes, getting lazy...

The typical problem with the 168-tooth flexplate is the starter is kicked out farther from the engine centerline and hits third gen headers.

You also need to know whether your 383 was internally or externally balanced. Did the engine builder tell you to use a weighted damper, or a standard neutrally-balanced piece?

Thanks five7kid!

I will have to look to see how much room I have with the headers tonight, thank you very much for the heads up. If it's close, I would hope one of those mini starters would be sufficient enough to accommodate.

It does seem that thinngs are pointing to changing it out for the smaller flexplate . It slips my mind whether or not the motor was internally balance, I'll have to double check with the builder.

Yes, it typically does. My bad, I didn't click on your starter link until after I posted, and was going to say, "Use a mini starter with a 168-tooth flexplate."

Well, not necessarily.

That is critical. Don't buy any parts until you know for sure.

Now that I think about it, where did the 168-tooth flexplate come from?

Thank you sooooo much for your time and input five7kid!

That is great to hear about the mini starter!!

I am unsure as to where the flexplate came from. It should be a new part that the builder got. The builder did not have capabilities to run the fuel injection on the motor, but he did throw a carb intake on it to run it before he handed it over. The motor had the current flexplate and damper on it when he ran it. I am hoping the info on whether the engine was internally balanced is on my reciept, otherwise, I will find out from him. I'll also check the reciept to see if there is a name brand or part number for the flexplate.

If he ran it with that damper and flexplate, they are the correct parts.

The flexplate will have a weight on it, as all 1-piece rear main seal flexplates do.

You might as well run the flexplate and damper that he put on it, and the ministarter. You could look at the damper to see if it has a weight on it, but there's a good chance it is internally balanced.