open chamber or closed chamber heads?

[68chargerboy]

what is the diffrence? i planning on a 528 stroker kit topped with a blower and the open chamber heads from indy are 82cc's instead of the closed at 75cc's.  the open would be better to help lower the comp but is there hp loss by using open chambers?

Thanks
Zach

[Cooter]

EVERYTHING Changes when dealing with compression ratio's when you are talking Stroker engines...ESPECIALLY, Blown ones! You don't want, nor need alot of compression. It's only a "Loss" with open chamber heads if you are normally aspirated, with a blower, you aren't concerned with it, as you are stuffing the engine with air/fuel..But to answer your question using normally aspirated engines as an example, I've seen "Open" chamber style heads on a 512 and DISHED piston's still come up to around 10.75:1 Compression....Remember, you are cramming ALOT more air and fuel into the cylinders by pulling the piston further down in the bore with stroker motors...The main reason for the "Closed" style combustion chamber on cyl. heads is for the  "Quench" area. Really, The only time Closed chamber heads come into play is iron headed street engines looking to bump the factory compression a little and not have to buy Domed pistons to do it...You will need to talk to your engine builder on recomendations as far as what type of Cyl. head will work best on YOUR engine..Back in the day, when your '69 Charger or whatever, had an "HP" 440 with open chamber "906" heads on it, and you wanted to bump it up a notch, you went out and got yourself a set of closed chamber heads..Today, with all the different, modern piston choices this isn't nessesarily the best way to go...The "Quench" area is the flat area of the head that extends over into the cylinder on closed chamber heads. open chamber heads (at least with iron heads) don't have this as the chamber edge goes all the way out to the edge of the bores...
To compare an iron closed chamber head and an iron open chamber head side by side, you'd see a small "pocket" where the valves are on the bottom of the head, usually shaped like a "D", or a "Heart" shape around the valves..With an open chamber head, you'll see that the combustion chamber "Pocket" goes all the way out to the edge of the bore and is completely round. More CC's (85 VS 75) in the open chamber than in the closed chamber..The smaller the CC number, the higher the compression with the same piston..Hope this helps..

[68chargerboy]

more then enough info!!!!    THANKS!!  and you talking to my engine builder now lol.  i read alot and ask alot of questions.  i dont trust other people to do any work on anything i own lol so i do it all myself and safe a bunch of coin that way too!