Piston dish

[Brianj5600]

I was excited when I got my last box of stroker parts today. I'm building a 4.7 with around 9.5:1 and .035" quench. I was disappointed to see the "D shaped dish". I want to run 87 octane, but the dish is practically round. I don't think I want to use these. How much turbulence would I be giving up?

[Cheromaniac]

Probably not as much as you think because the turbulence is induced by the kidney shape of the combustion chamber.
In any case, you need a 26cc piston dish to achieve the combination of a 9.5 CR and 0.035" quench. That's difficult to achieve without enlarging the area of the dish as well as deepening it.

[Brianj5600]

Had I known the dish was so big I would have gone smaller and found a few cc's in the combustion chamber, which I might still do.

[Cheromaniac]

The sum of the combustion chamber volume and piston dish volume will need to be 83cc. If you can enlarge the combustion chamber to 62cc, you can reduce the piston dish to 21cc.

[Russ Pottenger]

Hi Brian,

Yeah that’s not a particularly well laid out reverse mirror dish.

I wouldn’t worry about it too much, but if there is ever a “Next Time” i’d be happy to send you pictures of my design which is much closer to the reverse mirror image of the combustion chamber.

~Russ~