Question: Machining piston dome to reduce C.R.

I'm not finding the exact piston that I would like for my next 427 build. I've always had good luck with TRW pistons, so I'm trying to make do with what they offer. With a 110cc chamber, one set gives me a 9.07 cr (lower than I would like), and the other gives me a 10.83 cr. I'd like to shoot for a straight 10.0, due to octane issues and long term engine durability on track days. What's involved in trying to machine off a portion of the dome? It's a simple concept, and I could probably easily calculate the decrease in dome height required, but what equipment is usually required to do the machining?

Thanks,
Mike

Any adequate mill such as a Bridgeport can do just the tops. Making the fixture would be the most difficult/time conuming.

The amount of material left would be a determinimg factor.

Consider these guys, arguably the best pistons around.



Been using them since the early 70's. Surprisingly affordable.
They make their own forged blanks if you are that adventurous, or will produce finished to your specs.

A friend of mine used to machine pistons from blanks, I'll try and get some more info.

I did some math, and assuming I did it correctly, I come up with a DCR of 9.5 with the 10.83 pistons and an intake closing point of 43* ABDC. Anybody have any opinions on if this is too high of a c.r. for 93 octane. I'm hoping the aluminum aspects of the engine might cut me some additional slack and reduce the incidence of knock.
Thoughts?

69427 said:

I did some math, and assuming I did it correctly, I come up with a DCR of 9.5 with the 10.83 pistons and an intake closing point of 43* ABDC. Anybody have any opinions on if this is too high of a c.r. for 93 octane. I'm hoping the aluminum aspects of the engine might cut me some additional slack and reduce the incidence of knock.
Thoughts?

Click to expand...

The new ZZ4267 has a compression ratio of 10.1-1, and is supposed to be able to run 92 octane pump gas.
I would use a thicker head gasket before thinning out the piston top, but that is just my instincts.