GM Piston ID

**Caseys69** · #1 04-30-2019, 02:25 AM

A friend has a set of original pistons and we cannot seem to find anything on them. The number stamped on the top of the piston is 3875909

**dvss1** · #2 04-30-2019, 03:04 AM

Are you sure thats the number? Could it be 3875905? 3875905 is first design hi perf 396 oversized piston. I looked at a set at the Jefferson swap meet over the weekend.

**Caseys69** · #3 04-30-2019, 03:09 AM

I just posted a pic, its definitely a 9

**dvss1** · #4 04-30-2019, 03:17 AM

Yes definitely a 9. I would measure the piston and see what the OD is. Looks like a 396 piston.

**dvss1** · #5 04-30-2019, 03:20 AM

Are there any Numbers on the inside of the piston?

**Caseys69** · #6 04-30-2019, 10:43 AM

Its just stamped TRW on the inside