I know the three design types of pistons are the dome, dish, or flat top. Which are the better performer? What quality do each of these have in an engine for performance? TIA

 

I tend to like flat tops for street cars but for a drag car I would go with wedged pistons to get that CR up there

 

Todays's engine designs benefit most with flat top pistons. It allows the best flame travel across the piston. Dished pistons are designed to lower the compression ratio to either use lower octane fuels or to allow higher boost pressures with NOS, turbos or superchargers. That's why those add-ons are so popular on factory engines. Domed pistons will increase compression ratios allowing higher octane fuels to burn better. Depending on the engine design, a flat top piston with a small combustion chamber will actually work better than a dome piston at increasing compression ratios. The drawback is that a combustion chamber can only get so small before it's design become ineffective.

Some engines work better with different types of pistons and heads. A 350 works very well with flat top pistons and 64cc heads to increase compression ratios while a 454 works better with large open chamber heads and dome pistons.

Top fuel engines only use 6:1 compression pistons but are ramming enormous amounts of air into the engine from the blowers to produce 6000 HP. It's all in how the engine is designed that decides what piston to use.

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87 IROC-Z SuperPro ET Bracket Race Car
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87 IROC bracket car, 91 454SS daily driver, 95 Homebuilt Harley

 

i prefer flat tops too and they promote better flame travel than domed pistons. i've read dished pistons increase the swirl effect and make it easier to light the air/fuel, but are lower compression.

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there is a theory that says a properly dished piston (actually a reverse dome), will make more hp than a flat top. But, this requires you move the combuston from the cylinder head area down to the piston area. This requires a really small combustion chamber and other issues to make it work. (it's actually how nascar 9.0 motors are assembled). But, since most don't not have access to the info or the parts (you need to be able to move the chamber volume anywhere from 45 to 60 ccs in many cases) accomplish this, a flat top is a better choice.

 

If you do decide on a dome, keep it under .125" and grind/sand a "U" right under where the spark plug sits. This helps flame travel although a small cr loss happens.

I decided on domes for my engine since I need new pistons because I botched my .030" job with the hone and ended up at about .038" so I might as well keep going....

I ordered those Speed Pro hyper pistons with the coated skirt... They claim 10.68 CR with a 69cc chamber which sounds pretty good to me with aluminum.