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Does an open chamber head create more power than a closed chamber head, given the same compression ratio? How is flame travel affected between the two, doesn't the flame have to travel over more of a piston dome in an open chamber head? Does the flame not spread out as much in a closed chamber head?
I'm debating between a 119cc head and a 113cc head. Or maybe this is not a debate on closed chamber and open chamber, but rather bigger or smaller chamber.
Brian
Open chamber makes more power due to the breathing ability and flame travel. Closed chambers were about 109 cc. Not interchangeable without changing pistons (unless you are flat topped.)
I just went through this with this 540 I am building. I decided to go 119 cc head and do the compression with the piston. Had this been a Pro Stock deal I would have gone the small chamber (113 cc open) deal for max compression. But if the customer wants a blower (and most do down the road....or should I say river :D ) then the 119 chamber would make it easier to get a piston for blown gas or even blown alcohol. Compression wise. If any of that helps you.
The open chamber doesn't shroud the valves as much and promotes better breathing.
But to get the full benefit is to get the quench area as tight as possible!..
With open chamber (top drawing) the path around the valve is more unobstructed than a closed chamber head leading to better flow (flow still obstructed by the cylinder due to the orientation of the valve to the cylinder and the valve angle)
Accept for the new heads being made today (lower drawing)....The valve angle is much more upright in relation to the cylinder and the short turn is much greater leading to MORE airflow. Leading to the combustion chamber being made as SMALL as possible (along with added quench area.....alot more) so gasses are moved to the center of the combustion chamber in the smallest area and burned more effieciently and produce much more POWER to the piston.
http://www2.***boat.com/image_center...en_chamber.jpg
This is why the Hemi ProStock cars are NOT dominating the series. :D
The open chamber doesn't shroud the valves as much and promotes better breathing.
Hey, Stick to the non GM stuff, will ya?..But You are Correct as usual.There are some semi open chamber heads, fully closed and fully open chambers.I had a 454 with flat top pistons and closed chamber heads,107/109cc. They worked well for low H.P.and rpm.I ran this set up at 5200rpm.That was until I understood how important a large oil pan was. Also Hyperu- pistons do not work.
i have a 496 thats hardblocked with a callies crank and carillo rods and cast iron 105cc closed chamber heads, was wanting to change pistons to 15:1 with a birdcatcher inj with alcohol and 2 stage 400hp Nos,heads have been completly reworked with ss valves, trple srings, tita retainers, all this was done before i got the boat. my question is with these heads work (right) or do i need to go to an open chamber head. Thanks for your time Dan
with the block empty you can set the heads on and scribe a line by the chamber and extend the sides of the chamber out to the edge of the bore to unshroud the valves and still retain the double quench area of the closed chamber head. I have used quite a few of the 96 cc oval port heads with good success at fairly high comp on pump gas due to the small chamber being more efficient burn wise than the open chamber. to get the high comp with the OC heads requires a large dome which slows the flame front.dart big chief 14deg heads come with a 75 cc chamber and the 18 deg heads with an 85 cc chamber, big power with minimal timing. the new sbc I'm doing has dart 49cc chambers for highercomp with minimal dome for a 15-1 gas motor. things are better than when we scrounged junk yards and swap meets looking for hipo chevy stuff and hoped for the best. Now just whip out a catalog and credit card and get tricker shiot than we even dreamed of back then :jawdrop: