flat top or dished pistons for boost
 

For a Dart Little M based 400 small block build which would you use with forced induction? I found a set of Ross flat tops I like but they are only rated for 8 psi. There doesn't seem to be a lot of turbo flat top pistons available. My thought on the flat top would be the top of the piston would be more of a uniform shape and thickness IE be stronger than a dish. I can go either way as I'm getting after market heads with either 64cc or 76cc chambers depending on what pistons I use. The turbo will be a BW S480 and I'm not looking at running anymore than 20 psi with a 2 bar map sensor. I was told using the Chevy Cobalt 2 bar map is actually more like a 2.5 bar as it can read past 14.7 psi. Anyway which would be better and why?

I would agree that a flat top piston would be stronger but if you get a good name part you should never have a problem with a dish piston. 16040747 part number 3 bar map is what I used, works real well and its cheap.

Flat top is a better imo but you will need to run larg chamber heads. The custom 4032 Autotec's I have been using have a really nice small dish.

Is there a problem with running larger chamber heads? Seems to me like it would unshroud the valves more.

A 400ci sbc with flat top piston and 76cc head will be 10:1+ cr ratio. If you want that much compression it should work out.

I want to keep the power up when its not in boost. Its going to have aluminum heads running either a 170 or 180 thermostat and its intercooled. Should still be pump gas friendly up to 12 psi or so. Even 10 psi will add a lot of power on an engine thats going to make well over 500 hp NA.


Can someone point me in the right direction of a flat top specifically for forced induction? This is the ross piston I was talking about earlier. How is an extra heavy duty forged 2618 piston only good for 8 psi?

Ross Racing Pistons Products

Bump.

Good quality pistons will have extra material in the dish portion on the bottom side to make up for the lack of material on top.

I think both will be fine. Your decision needs to be based on how much boost your going to run.. I think 10 psi will be doable with flat tops. But if your serious about running 20psi, you have to go with dish.

I have extreme duty JE pistons in my 400. They will be at 21 PSI. Only run a 6.0 rod max unless you are going to get a raised deck so you can get as much material up top as you can fit. I will grab the part # when I am done with work.