[351C]

Whats the difference between quenched closed and open chamber heads?

Lets say on a 351 cleveland

and what would be the best?

[artistang]

If your combustion chamber is perfectly round, you have an open chamber head. If it is 'D' shaped or heart shaped or any other shape that creates a 'quench' area, then it is a closed-chamber head. When the piston is at TDC, the clearance created by the head gasket thickness in a quench chamber between the top of the piston and the cylinder head cools the piston and creates a high velocity flow. The open chamber does not do this therefore a dome or pop-up piston is necessary to create sufficient compression ratios.

I think 351 clevelands had two different style heads for the same engine. The 4barrel heads had smaller combustion chambers for more compression and better "quench". The 2 barrel heads had much larger combustion chambers for low compression.

What is best for your application is dependent upon the purpose of the engine.

[dadofbadmofo]

Open chamber 351C heads have a large combustion chamber - the closed or quench heads have a small combustion chamber. The quench heads are the desired heads - but, the open heads work OK with the right piston (small dome) to get some compression out of it. The 4V heads have larger ports than the 2V heads. The 2V heads work OK for the street - give more low end torque.

[silver69]

Currently running 4v High compression heads on my 72 Mach 1 with a 4R70W 4spd auto w/ lockup, comp roller cam(mildest one) and 3:50 limited slip.
I know everybody claims these heads lack low end but I say bull. this engine makes incredible power ALL over the band. If I power brake and bring it up slowly the rear tires begin to turn over at 1200 rpm and I can keep it sideways to 6200 rpm. I can go 25 - 30 mph and stand on it - lights them up too, the best part is she is such a sleeper and will smoke so may cars, havent run down a vette yet but I drove an 08 and all I can say is "damn" what a rush! My mach idles nice and smooth, nice quietish duals, spent a year building it and everything is new and body and paint turned out better than I tought I could do on such a "big" car. I do not want to sound pompus believe me but I am merely proud of the final product. I just saved up enough to buy a MassFlo EFI system so that is my next upgrade.
I had 351-C 2V in a '71 1/2 sports coupe years ago and it was weak on top with almost as good on the lower band.
Sorry all I should have probably put all this babble in talk insted of tech...

[mycoses]

I ran closed chamber (quench) heads in my 72 mach with flat top pistons and got a lot of ping and knock pushing on the pedal. (too high C.R. )Switched to open chamber heads and the ping disappeared. Now I can push the pedal with impunity. Could not notice any seat of the pants difference in power but now I can push harder on the pedal so maybe that made up for the difference.