I have always been under the impression that a Closed Chamber head has a Performance advantage over an Open Chamber head.

An example for the mopar guys a 1967 440 head is closed chamber and can be replaced by a 1968-1970 head that is open chamber because the head gives no performance advantage.

Would the same apply to a 188 casting GM head being open chamber to replace a 088 head that is closed chamber.

Lets hear your thoughts.

Has to do with quench. Closed chamber has more quench which helps keep fuel in suspension. reduces octane requirements.

http://www.crankshaftcoalition.com/wiki/Quench

So your link is saying no advantage?

I don't think there's an advantage going to open chamber, harder to obtain squish/quench

Unless you can get a piston that would give you more square area of squish due to it being a raised dome piston?

Hey remember your one pushrod that over heats. Dry film lubricant, if it works for valve stems.
your pushrod cup should be fine.

http://www.competitiveedgecoatings.com/ ... ricant.php

IMHO... you want a tighter quench area. Not sure how others feel about pistons, but I always try to use a flat top whenever possible... better flame travel.

Now where there could be an advantage of an open chamber head is - better combustion chamber design. Despite having a larger chamber, some of the newer open chamber heads may have a better design that promotes better swirl in the combustion chamber. I know in the BBC oval port heads, the 71'+ head castings (820, 241, 292, 049, 781) have a better designed chamber than the 70' and older closed chamber heads. (290, 280, 215, 390, 702) My factory "241" castings started off at 113cc, I had them cut down to 100cc to get my SCR up. I could have used a 70' style LS5 piston to achieve more static compression, but at the cost of flame travel. I never flow-benched my heads before and after to see what milling did to the swirl in the chamber.

Open chamber is prefered and are more readily available, but the closed chambers can be opened with a little work, and squish and quench can be altered by design of pistons.

With open chamber, the oem just did the work for you

With that said, i see no reason they cannot be interchanged as long as outward appearance is correct and theres no other otherwise unobtainable advantage, aka, an advantage that cannot be reached thru porting etc.

Btw, i have experienced and heard of many heads ruined by porting, so going bigger is not always an advantage!

No "size matters" jokes please! Lol

I guess you could argue the question either way but in the end the engine build with an open chamber head or a closed chamber head wil in my opinion not be much of an advantage either way. Gm did replace some of the old closed chamber heads with bolt on open chamber heads .