I'd still like somebody to explain to me where quench is taking place with a heavily and fully dished piston. That 1/4" wide ring around the outside edge of the piston that only comes close to the head around about 1/3 of it's total circumference? That's enough area to have meaningful quench?

If so, I guess I was wasting my time putting d-dish pistons into my blower motor when I could have just slapped some open dish slugs into it and gotten the same results. For that matter, why have d-dish pistons at all? Marketing hype?

 

i would think that d-shaped would be better...

 

Damon,

Take a look at a chamber on a cylinder head with the head gasket ring etched into the surface. You'll see on the part of the head that's opposite of the spark plug that there is a flat pad there, that's where you don't want air/fuel, on the opposite side of the bore from the spark plug. The pistons just replicate that.

Ultimately what you want is a piston that is a mirror image to the chamber.....

Not easy unless you have the chambers profiled on a digitizer and then a dish designed into the pistons....

Here is a good look at this.....
http://popularhotrodding.com/enginem...r_emc_13_z.jpg

That's a common thing on motors that are compression ratio limited and the cylinder head has a small enough chamber to allow this.... NASCAR 9:1 motors, are a good example.

Is it marketing hype? Every shop that builds Busch motors doesn't think so, Jon Kaase doesn't and I'm willing to bet that Mindgames 650+hp 383 doesn't either.

Bret