i just got my 383 stroker engine from the shipping company. the block casting number is 10243880 which tells me "350...95-00...2 or 4...Vortec truck, Gen.I crate motors and "ZZ4", roller cam, one piece rear seal"

the engine was supposed to be a 87+ roller block with one piece rear seal crank, but my flexplate is not fitting on the end of the crank (crank to big), which leads me to believe its a 2 piece. the engine was internally balanced. is this a 2 piece rear main? if im mistaken and it is the 1 piece rear main, which flexplate should i use on it.

 

It's a 1-piece RMS block, with an adapter to fit a 2-pc type crank; and of course a 2-pc crank.

A 1-pc crank has a completely round flywheel flange, such that the aluminum seal plate that's bolted on behind the crank, can slide over it. The 1-pc seal is just exactly that: one piece; a metal-clad lip seal, like a wheel bearing seal or something. It couldn't possibly go on over that other shape.

You should use a regular old-style flex plate for 2-pc RMS on it.

 

thanks for the quick reply. that was one of my assumptions that it was a 1 piece block with a 2 piece adapter. why would they do this? why couldnt they put the 1 piece crank in there. is there any pro/cons to this adapter? pros/cons for 1 or 2 piece crank shaft. should i complain and get them to install the right crank without the adapter. i know the 1 piece cranks are a tiny bit more expensive, not much, but i paid for the 1 piece, not an adapter to hold the 2 piece.

i really wanted the 1 piece so i could reuse my flexplate.

 

They do that because 2-pc cranks are often ALOT less expensive. Especially for the internally balanced variety; since part of the internal balance weight is that funky shape on the flange.

Which is probably (hopefully) reflected in the price you paid. Generally, when you shop for a motor and go for the lowest price one you can find, you should expect that the seller will also do everything possible to reduce their costs. After all, it's not possible to run a business for very long by buying dear and selling cheap.

Often, the difference in the cost of the crank and machine work, is greater than the price of a flex plate, which is basically a little bit of nothing.

No I don't think you should complain. I think you should enjoy the savings on the price of the motor that allowed you to get such a good deal (you did, didn't you? ...), and just get a flex plate. They're REAL cheap; like $35 or less, for the equivalent to what I'm guessing you have now (stock).

There are no particular "cons" to the adapter. The "pro" is obviously a lower-cost short block; or to look at it from the flip side of the cost/benefit equation, more short block for the same money.

 

so which flexplate should i use. 153-tooth? neutral balance? internally balanced, 2 piece RMS.

kind of like this one from summit? SUMMIT RACING - FLEXPLATE - TCI-399573

 

That one would do the trick. A good bit more $$$ than a stock replacement one; but a far better piece too.