L:88 piston ID

[JHS]

Anyone know the TRW/GM part# that should be stamped on the top of a L88 Piston?

[Mr70]

It looks like the Std. bore TRW/GM 1969 L-88 piston was #3959105,to be used with the "New" #074 Al. head w/118.0 cc.
GM #3959106 was .001 oversized.
GM #3981891 was .005 oversized.
GM #3959107 was .030 oversized.

They list another one,which I think was specific to the 1968 Corvette L-88 which used the #842 Al. Head. w/106.8 cc.
They are:
GM #3909857 was Std. Bore.
GM #3909858 was .001 oversized.
GM #3909859 was .030 oversized.
GM #3909860 was .060 oversized.

Sometimes the last 4 digits are pressed in them.

[JHS]

Thanks for the info.. I am trying to determine if my car has the L-88 pistons in it without pulling the engine. I have scoped the pistons and they appear to be the big dome ones and have a number (hard to read)stamped into the top of each piston but those numbers you gave me do not match what I THINK I see. The car has open chamber 990 heads on it and a pretty radical cam so I think they are L-88 style.

[Born30YrsLate]

perhaps they are LS-7 pistons...those are dome pistons similar to the L-88s, except for the LS-7 454 engine which also used 990 heads, it got a healthy cam too...just a thought

[Mr70]

"and have a number (hard to read)stamped into the top of each piston "

What number do you see?

[JHS]

Left it at home so will post later. I do know that the pistons do not have an over bore size stamped on top so assume it is a std. bore.

[JHS]

Here is what I THINK is stamped on top of the pistons:
L2808A. I am unable to get a clear shot at the stampings due to my scope not having an optical extension with a "memory". I can not bend the optic cable in a stationary position in order to get a good view of the lower top side of the piston where the stamp is.

[my69396]

i have a set of pistons with 3947886 on the top and was wondering what they fit. thanks jerry

[Mr70]

That's the actual casting number for GM piston #3959105 mentioned earlier,which is the Std. bore 1969 L-88/ZL-1 piston.