Difference between open/closed chamber?
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Post Fiend
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From: Missouri
Difference between open/closed chamber?
Since this seems only to be talked about wne referring to the cleveland I thought this would be the place to ask. Not sure what this is referring to.
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From: PacNW
Difference between open/closed chamber?
When referring to Cleveland heads open chamber means that the combustion chamber is large relative to the overall displacement of the engine i.e. +/- 76-78 ccs. The shape of the chamber itself is a multi-angle dome with the valves set at different angles.
A closed chamber head has a much smaller combustion chamber, +/- 58-62 ccs and the valves sit in a "pocket" for lack of a better term while the rest of the chamber area is flat and even with the surface of the head.
There is a good side by side picture of open and closed chamber heads on this site:
[link:members.tripod.com/lyc_42/fordv8/cleve/cleve.htm|335 Series Page]
A closed chamber head has a much smaller combustion chamber, +/- 58-62 ccs and the valves sit in a "pocket" for lack of a better term while the rest of the chamber area is flat and even with the surface of the head.
There is a good side by side picture of open and closed chamber heads on this site:
[link:members.tripod.com/lyc_42/fordv8/cleve/cleve.htm|335 Series Page]
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From: Virginia
Difference between open/closed chamber?
Most engines, most brands(not just cleveland), had a "closed chamber" style head in the 1960's and very early 70's. The "open" chamber heads came along in the 70's to lower compression. In the early 70's you could have either/or depending on performance ordered, but by the late 70's, everything was open or large chamber. One way to tell the difference is the metal of the head seems to hug the valves, with a irregular shape to the chamber. The open heads have a large round shape to them.
What seems to be the big deal as far as power, is called "quench". If you look at a closed chamber head, picture putting a 4 inch round piston up against it. Right around the valves and the sparkplug, there will a hollow area, but the rest of the piston will have little area between it and the head surface. They claim, besides raising compression, this area actually forces the air/fuel mixture over to the sparkplug and helps combustion and resistance to spark knock. I don't fully understand it, but the newer fuel injected cars are going back to the high compression closed chamber heads.
What seems to be the big deal as far as power, is called "quench". If you look at a closed chamber head, picture putting a 4 inch round piston up against it. Right around the valves and the sparkplug, there will a hollow area, but the rest of the piston will have little area between it and the head surface. They claim, besides raising compression, this area actually forces the air/fuel mixture over to the sparkplug and helps combustion and resistance to spark knock. I don't fully understand it, but the newer fuel injected cars are going back to the high compression closed chamber heads.
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