GM piston numbering

[CantRepeat]

Goodday,

I'm in the process of rebuilding my 67 350 and I'm trying to figure out how GM numbered oversized pistons.

The factory pistons in are GM 3892673. The block needs to go 30 over; would the part number just add a -30 to it?

IE GM 3892673 -30 for .030 oversized? Looking at some documentation GM made replacement pistons in both 4.0287 and 4.0307 sizes.

Thanks for any insight.

[bcmiller]

The number you are looking at is a casting number and that is usually not the same as the GM part number.

Honestly, if it was me, I would go with new pistons. The new aftermarket pistons these days are an improvement over the originals.

[bcmiller]

Here are the part numbers.

Oversize pistons are typically stamped as such on the top face of the piston. I will look to see if I have any examples. I do have some oversize 427 pistons.

Here is the chart from a parts book.

[CantRepeat]

Thanks, Bryon. I would like to keep the engine as factory as possible. So, I'll see if I can find some of the 3911023 pistons.