HataErasa

iTrader: (1)

What differences are there?


Does the flame front travel better on the flat top?

I am looking at getting a set of AFR 225's, right now I want a pretty salty NA motor that will occassionally see the juice. But at some point I may go forced induction. I am just curious as to how much is left on the table when you go with a large chamber design and build compression by putting in a dome piston.

Many Thanks

SStrokerAce

iTrader: (2)

Depends on the shape of the dome. Normally a flat top application can do better but a well done dome doesn't hurt.

Bret

Ryan02SS

iTrader: (3)

You want all the sharp edges if any on the dome taken down to help prevent detonation.

SStrokerAce

iTrader: (2)

Not just the dome EVERYTHING in a combustion space shouldn't have a hard edge.

Bret

CNC BLOCKS N/E

We have seen using a dished pistons there is horse power gain.

MUSTANGEATER

iTrader: (10)

Are you reffering to

Big Chambers + Dome

vs

Small Chambers + Dish

or am I missing your point?

Old Geezer

iTrader: (3)

Less/no dome, small chambers, and good quench numbers, beats the alternative.
We saw that in use, some 15-20 yrs ago, with the BUICK Stage 2 heads, and the NASCAR Busch engines. Worked VERY well.
Currently running a 274" Stage, on the street, 11:1, carbed, right at 500FWHP.... No led premium.

Back to

SStrokerAce

iTrader: (2)

Yes at a set compression ratio the right small chamber/dish setup usually makes more power.

Bret

HataErasa

iTrader: (1)

I am looking at about 10.5 to 11:1 compression ratio.


trying to decide between the big and small chamber heads.

The big chamber will be more versatile for me

Is the difference in how the flame front travels across the piston, that yields better results with a flat top piston?

gun5l1ng3r

So the size of the chamber does no change flow characteristics?
I would think, like with a bigger bore, a bigger chamber would un-shroud the valve more...

I guess with the same size valves, how big the chamber is (within reason like~59cc-67cc) doesn't matter.

SStrokerAce

iTrader: (2)

Yes the chamber is a balance between flow and burn... to me I'd rather have the burn than the flow, there is more power in the burn.

If we are talking about 10.5-11:1 compression what's the point here? YOU DON'T NEED A DOME TO GET THERE. Just do whatever, your not pushing the limits NA and my guess is that your not going to spend the coin on the pistons to do a small chamber/reverse dome setup that would make for the quickest burn so what's the point here?

If you are building a NA motor to put a blower or turbo on later on you need to change a bunch of parts anyways. Either the chambers, or the pistons and the cam at minimum so WHAT are you trying to do here? Seems pointless to point you in some direction when you are the only guy who knows what you are attempting to do.

Bret

HataErasa

iTrader: (1)

My question is how much efficiency would I be losing if I went with a dome piston in a large chamber head, Specificaly the AFR 225 with a 72cc chamber.

and lets say this is at 11.5:1 running pump gas

I am also asking if there is a loss , is it related to flame front travel across the piston?

SStrokerAce

iTrader: (2)

Are you stuck with the 72cc head or something???? This doesn't make sense to me.

HataErasa

iTrader: (1)

no it would just be more versatile as if I eventually switched to forced induction that would be what I need. Plus If I ever sell them I think it would be easier to move them for someone with a supercharger.

The reason I might switch would be to go up to a LS7 head eventually.

I like the idea of being able to switch between several different setups.

I am not however understanding how much is left on the table when going with a dome and a large chamber with compression being equal?

the.erinyes

iTrader: (3)

More than likely there will be no benefits although several downsides such as higher piston weight, more stress on rods and crank, higher emissions, less fuel mileage, and lower performance. Quite frankly if there were benefits to be found GM would have used them instead of a flat top piston with a smaller chamber size. In addition, the chamber should be designed to use the dome piston, which would not be the case since the 72cc head also uses flat top pistones.

SStrokerAce

iTrader: (2)

The Ls7 head will need a different piston anyways.... My rule is build the setup right, and put the right pistons to match the chambers and your goal, pistons have to be changed after a while anyways.

Bret

LSPerformance

iTrader: (23)

I prefer a flat top to any dome, if you must use a dome use as little as possible. In some cases I've seen specially shaped shallow dishes produce slightly more power, I think it may have had something to do with the intake charge being more centered in the piston during the ignition/burn process.

avitet

if it were me id use flat tops and suffer the lose of power to start with and make up the difference with the bottel until you switch

HataErasa

iTrader: (1)

well in that case, are there pistons out there with enough dish to go to 8:1 when you are using a 62cc chamber?

SStrokerAce

iTrader: (2)

WTF would you want that little compression for?