SB Piston GM part #

[Chris_Pisane]

Hi, I have a set of used pistons I got many years ago that I always assmumed were 69 302 pistons since they came with a 69 302 crank and pink rods. The part # on the underside of piston appears to be a GM #3927172 TRW,they are domed. I checked the fact book and thats not the right one for 69.

I checked my chevrolet by the #s and they dont have part #s listed for pistons.

Any Help?

Thanks.

[Steve68]

Chris, can you double check that last number (2) to make sure you read it correctly?  Thanks.

Steve

[Chris_Pisane]

3927172. There is an L under that number

Thanks

[JohnZ]

3927172 is correct - that's the FORGING NUMBER, not the part number; the part number won't appear anywhere on the piston. That raw forging was finish-machined into several different PART numbers for the standard bore and oversizes.

[Chris_Pisane]

OK, lets see if I get this straight. It is a factory 302 piston,right?

The TRW forging  nuimber is  like many GM part #s of that era,even the same number of digits, thats is why I assumed it was a GM  part number.

I have some 70s vintage overbore pistons and they actually have 2210A stamped on them,these dont.The forging # appears to be 186-99.

I knew John Z would have the answer,correct me if I misunderstand. THANKS!!!

[JohnZ]

L2210 is the TRW 302 aftermarket finished piston number; the raw forgings TRW supplied to GM for OEM use had the 3927172 GM forging number on the underside of the crown; the final cam-ground machining of the pistons in production was done at the GM engine plants.

[69z28rsbilly]

I have some TRW pistons with casting # 3927172 on the bottom side and 3927173 stamped into the top. They look to be standard and never used.
 Is there good way to tell if the pistons have been used or not ?

[Jerry@CHP]

One small note, all of the over the counter TRW pistons use the thinner piston rings.  Keep that in mind too.

Jerry