Thread: 350/383 rear main seal

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I am getting ready to change the rear main seal what is better a one or two piece seal? I don't know if he has a crank that is custom for a 383 or if he has a 400 crank, how can I tell, and does this make a difference when selecting a rear main seal?

If you have a 383 stroker, you won't have a choice on which seal to use, it will have to be a 2 piece. All GM 400 cranks (which the majority of strokers are built from) are designed for the 2 piece seal. As far as I know there are no aftermarket cranks available for the 383 strokers that are designed for the 1 piece seal.

The good news is the the 2 piece seal does not involve the removal of the engine or transmission as the 1 piece seal does.

THe guy that I bought it from had said the one in it right now is a one piece, does that sound odd?

I'm not saying it's impossible, but the engine would have had to have build from an 86 or latter block (when they converted from the 2 to 1 piece seal) and would have to use a corresponding crank designed for the 1 piece seal. As I said, "as far as I know" no one is making a stroker crank designed for the 1 piece seal. Short of pulling the pan, list the casting number of the block, from there it shoul easy to determine which seal you will need, and what procedure you will have to do to change it.