L88 open chamber pistons

[Joe L.]

Re: L88 open chamber pistons

Ed-----

GM #3959110 is a forging or casting number. It was used for the 1969 open chamber L-88 and ZL-1 pistons. However, it may have been used for all of the various sizes of this piston. Forged pistons of standard and various over-sizes for a specific application are often manufactured from from the same "slug". I don't know, for sure, if this was done for the open chamber L-88/ZL-1 pistons, but I'd say it would be very likely. In any event, I don't think that anything other than the open chamber, L-88/ZL-1 pistons were manufactured from the 3959110 forging.

So, I'd say that if the pistons are standard bore size, then they are GM #3959105, irrespective of what part number is shown on the box. Measure them carefully, though, as there was also a +0.001 oversize once available. This was GM #3959106.

[Joe L.]

Re: L88 open chamber pistons

Ed-----

GM #3959110 is a forging or casting number. It was used for the 1969 open chamber L-88 and ZL-1 pistons. However, it may have been used for all of the various sizes of this piston. Forged pistons of standard and various over-sizes for a specific application are often manufactured from from the same "slug". I don't know, for sure, if this was done for the open chamber L-88/ZL-1 pistons, but I'd say it would be very likely. In any event, I don't think that anything other than the open chamber, L-88/ZL-1 pistons were manufactured from the 3959110 forging.

So, I'd say that if the pistons are standard bore size, then they are GM #3959105, irrespective of what part number is shown on the box. Measure them carefully, though, as there was also a +0.001 oversize once available. This was GM #3959106.

[Warren F.]

Re: L88 open chamber pistons

Ed,

3959107 is the number for .030 OS pistons.

[Warren F.]

Re: L88 open chamber pistons

Ed,

3959107 is the number for .030 OS pistons.

[Norris W.]

Re: L88 open chamber pistons

The 427 and 454 required a different pin height because of the stroke difference between the 2, so there is no overlap between L88/ZL1 and LS anything as far as pistons go.

Dick, correct me if I'm wrong, but I always thought the low compression of the '71 LS6 in the Corvette was obtained by simply putting the open chambered alum. heads on the 11:1 Chevelle block assembly from the previous year.

I bought a '71 LS5 car once, that as far as I know had the original pistons in it. When we had the heads off I noticed that the pistons were the same as the '70 LS5, so we stuck a set of closed chambered heads back on and woke it up. I don't know for sure that the engine was unmolested, but it was std. bore and had GM factory pistons from a '70 closed chamber motor and had THE original block, so that was the assumption, and perhaps what I based the conclusion on years ago that the LS6 was done the same way.

[Norris W.]

Re: L88 open chamber pistons

The 427 and 454 required a different pin height because of the stroke difference between the 2, so there is no overlap between L88/ZL1 and LS anything as far as pistons go.

Dick, correct me if I'm wrong, but I always thought the low compression of the '71 LS6 in the Corvette was obtained by simply putting the open chambered alum. heads on the 11:1 Chevelle block assembly from the previous year.

I bought a '71 LS5 car once, that as far as I know had the original pistons in it. When we had the heads off I noticed that the pistons were the same as the '70 LS5, so we stuck a set of closed chambered heads back on and woke it up. I don't know for sure that the engine was unmolested, but it was std. bore and had GM factory pistons from a '70 closed chamber motor and had THE original block, so that was the assumption, and perhaps what I based the conclusion on years ago that the LS6 was done the same way.