Say you have 2 identical engines, except one has 76cc chambers and domed pistons, the other has 64cc and dished, resulting in the exact same CR. Flow in the heads is the same...will there be any power difference? I've heard that the domed piston can cause ineffiecient burn in the chamber, and cost power...

 

i've heard same thing, but givin my limited resources never had the chance to built 2 engines and do dyno pulls. i've heard as far as flame travel across the chamber flat tops are the best, or make the least interferance.

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-=ICON MOTORSPORTS=-

 

i've herd that as well, it has somting to do with the way the flam travels, the domed biston acts as a barier, slowing travel down, making it less efeciant

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when the green flag drops the bull$hit stops

350,performer RPM intake ,650dp, 700r4, headers, 3inch exhast

 

Well some domed pistons have a little groove cut in the middle to aid in flame kernel propagation. I think that's quite an effective idea.

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92 Z28 L98 350
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Ported and polished heads, ported stock TPI base, ported plenum, Comp Cams XR270HR-10 cam (lift .495/.502 duration 218/224 lobe separation 110), Edelbrock TES headers, LT4 valve springs, Crane AFPR, Flowmaster catback with LT1 style tips, MSD coil & wires...

"Take that auto, drop it in first, hold the brakes, stomp the gas and grin from ear to ear! :-)

 

the smaller chamber head is much better. many reasons, but a few are :valve closer to cylinder, more room for swirl in the cylinder, less hot spots in the cylinder meaning more available timing, and more room for spark plug. this is proven in many ways including diesels with flattops and almost no chamber. even nascar uses like a 48cc combustion chamber. pretty much all ho heads on even factory cars are small chamber.

 

It's an age-old quandry. We all would like to have it tighter, and the trade-off may be in selecting one with less room in the head. On the other hand, getting one that is not as tight but perhaps a little more tolerable on a day-to-day basis with domes. The down side of that is finding a place to set your beer...

Oh, we're talking CYLINDER heads - never mind. There is something to be said for a tighter chamber, though.

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Later,
Vader
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"Make Me Bad"
Adobe Acrobat Reader 4.0

 

And I thought I was dropping 'em here and there! At least we think alike!

 

Alot of people I knew in the 70s and early 80s thought they would take a crap 8.5:1 165 HP 350, stick a set of "pop-ups" in it, port the heads until they hit water and stop and epoxy that back up, slide a "Stage II" cam in it, and they would be the king of the drive-in. It never seemed to work.

The heat cycle seems to work the best when the hot gas is in as nearly spherical a shape as possible. I've heard all sorts of things about flame travel and lack of turbulence in the chamber and a variety of other possible reasons; it probably has more to do with the actual production of power (expansion and cooling of hot gas) rather than merely how the gas gets hot.

I prefer the approach of a smaller, rounder chamber (less bathtub-like), with areas around the perimiter of the chamber where as the pistons approach the top they cause gas to "squirted" at high speed out of the edges of the chamber and into the center. The engine I have right now, for instance, is a 400 with 64cc 186 heads and 12.5cc dish pistons.

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"So many Mustangs, so little time..."

 

To be honest, I don't think there has been too much research done into flame front travel. My brother and a friend of his are experimenting w/ a new piston engine design. I can't say much about the project but I'll say they went looking for equations to describe the movement of flame fronts and found nothing. The only shaped flame front engine design I know of was the old mopar hemi's. They had power, but was it due to the head design? Maybe some old timers who actually got to work on 'em can tell that
Corry