Which is better - Small ccr with large dish or large cc with small dish

[jim_in_dorris]

Ok, I am trying to keep my compression ratio reasonable, so I have 2 choices. 15cc dish pistons with a 72 cc combustion chamber or 22cc dish pistons with a 64 cc combustion chamber. My thinking is that a bigger combustion chamber and small dish will keep the flame in the head rather than down in the piston. Am I over thinking this, does it make a difference? I am getting ready to order the rotating kit and need to choose the piston dish size to keep my compression between 9.2 and 9.5:1. Anybody have any educated reason to choose one over the other?

[1project2many]

This is a tough one, and the result will probably be a compromise. The volume of one chamber to another is not as important as the shape. A fast burn shape is more desirable than an older open design as it can make power with less ignition advance and laess fuel. Additionally, the quench distance should be considered. Piston quench distance under the head should be in the neighborhood of .045" - .050". This small distance creates a large amount of turbulence in the chamber while preventing the fuel/air reaction from progressing in the quench area. A larger distance reduces turbulence and can actually invite detonation or pre-ignition. Here's a nice, quick article about quench distance and also showing some piston shapes designed to help increase quench while providing proper piston volume: http://www.superchevy.com/how-to/engines-drivetrain/94138-piston-head-clearance-guide/

If this is for your 383 the choice might be tough. If the larger chambers are from an old design set of heads, I'd favor the smaller versions. But I'd look hard at the piston shape that I put underneath it. A "D" shaped inverse dome would certainly be better than a dish which occupies most of the piston top.
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FWIW.

[jim_in_dorris]

The quench would be in line with your numbers and the head is offered in both sizes of combustion chamber. They are Dart shp heads.

[1project2many]

Nice heads. I'd pick the smaller chambers and larger dish. If you ever decide to use the heads on a smaller displacement engine it will be easier to keep compression up.