What is difference and advantages ???

 

flat = "the norm"

dome = more/higher compression

dish = less/lower compression

 

Flat top



Domed



Dished

 

AS the above poster said.

Dished is better for nitrous or forced induction applications because it lowers your compression.

Dome is what you want when you want a all motor engine, you want a high compression with a big cam to get more power.

Flat top is just the norm.

 

Actually, there are some schools of thought that espouse themselves to the theory of using slightly dished pistons with tighter head chambers to raise compression.. The reasoning is that the slight dish allows better flame propagation for more efficient burning, and more resultant power. The dish still has to be kept smaller than what the factory usually did to provide enough quench area to cool the charge and control the flame spread, allowing a lower octane fuel while at the same time making this additional power. But it's technically a dish nonetheless.

At least, that's one theory that has become more popular lately.

 

Vader is right... flat tops/dished pistons and small chamber heads are a much better way to create high compression and the power that comes from it, than using domed pistons to create compression. Domed pistons are known for totally killing the flame travel accross the piston.

 

Don't forget the reverse dome and step-dome type pistons, from what I read it's the best if you wan't a good medium compression like 9 to 1 and a tight quench too. Mostly used on stroker engines like 383's

 

The pistons you choose, in many cases hinges upon what the compression will be with a given set of heads.
A piston that gives you the incorrect compression ratio is of no advantage at all.
With large displacement engines (strokers) the inavailability of a head with the nessecary volume to work in some applications with a flat top piston can make it nessecary to use a dished piston in order to lower the CR to a level that works in that application.

Hope that made sense...

 

Did any one notice the size and complexity of the words that Vader used: wow I feel ignorant. it took me a minute to just pronouce them

Who says us motor heads are not edumacated.

 

Didn't know that vader, i'll have to look into that more when I build up my stroker this year.

 

Work with me here...Back when I raced MG's (yes MGs, I can hear the laughing now) they did a big test on compression ratios since they only had 1275cc to work with. They discoverred that a dished piston with a smaller combustion chamber made more power than a pop up style piston. The piston they used was a "reverse hemi" similar to one of those shown above. Which, if you think about it, probably did allow for better flame travel and less ridges and crap that might create problems with pre-ignition.

 

blacksheep,

Who's laughing? I remember the old Midgets, Austins, original Coopers, and Truimph TRs running in a class at the local road race course (some still do), and they needed every advantage. There's little doubt that they would try to use the most efficient combinations possible, since they are so displacement-challenged. Some of us with less of a size challenge could still learn a thing or two from some of the "little guys". 75Hp/liter in the little 1.3 would translate rather nicely to a 305 or 350, wouldn't it? In some cases, it does.

Ever visit Blackhawk in your old racing days?

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pasky,

It almost always pays to do a little homework and research. I wouldn't even have a clue about this kind of theory if I thought I already knew the best way. Of course, we all know better than that. I'm here to learn like everyone else.

 

No, Savanah (Roebling), West Palm (Moroso), Daytona and Sebring in both sports cars and karts. As I recall Blackhawk was hell on brakes.

 

So to do this reversede piston thing you have to get the smallest chamber you can get that will correspond to the dish and desired compression ratio?

Would love to see some examples that are 383 and 400 applicable...

Jason

 

I would say yes, the heads we had just had enough "indentation" for lack of a better word, or combustion chamber to house the valves and that was it.