closed or open chamber heads

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09-28-2006, 10:31 PM
steelsixpack101

closed or open chamber heads

what are your guys opinions on oval port big block heads. closed chamber or open chamber. i know just a bout every hotrodder has heard somewhere that open chambers are better because of better breathing, but i know this guy who is highly religious with closed chamber heads and had very good success with them. of course he modified them. he was a very smart guy and ran the fastest times at the local track. He used late model (68-69) closed chamber where they are open up a bit by the factory, but not the very early ones that looked like bathtubs. then took the heads on a milling machine and cut back a bit on the exhaust(opposite side of spark plug) to unshroud the exhaust valve. then he milled .020-.025 off the deck of the head, put a nice three angle valve job and ported the ports and bowls. and lastly polished the combustion chambers. he liked closed chamber heads for a number of reasons
1. valve shrouding is really not that bad on the later(68-69) heads
2. you take have a smaller dome piston or flat top and it doesn't screw up the flame travel
3. the tighter and smaller combustion chamber gives a better and quicker fuel burn off which means you can usually run more spark advance.
4.port thses heads out and you'll have great flow.
09-29-2006, 10:29 AM
techinspector1

It sounds good to me although I've only built one BBC in my life. I've done SBC until I'm ready to gag on them. Maybe Pat McCarthy will come along and give you the scoop on 'em. He's the resident BBC guru on this board.
09-29-2006, 02:10 PM
1JohnnyO

There are pros and cons to both...I have run both, and had great results either way. I run the closed chambers now on my 505, because I already had them. I pretty much did what you said above...milled, mild porting, etc. I was able to get a 10/1 c/r with flat top pistons. Like you said, the flame travel is better without the dome in the way. But I dont think it's a huge factor either. I like the closed chamber heads. I know a lot of guys who are running them in a drag car and do very very well. John
09-30-2006, 06:51 PM
erik erikson

Quote:

Originally Posted by steelsixpack101

what are your guys opinions on oval port big block heads. closed chamber or open chamber. i know just a bout every hotrodder has heard somewhere that open chambers are better because of better breathing, but i know this guy who is highly religious with closed chamber heads and had very good success with them. of course he modified them. he was a very smart guy and ran the fastest times at the local track. He used late model (68-69) closed chamber where they are open up a bit by the factory, but not the very early ones that looked like bathtubs. then took the heads on a milling machine and cut back a bit on the exhaust(opposite side of spark plug) to unshroud the exhaust valve. then he milled .020-.025 off the deck of the head, put a nice three angle valve job and ported the ports and bowls. and lastly polished the combustion chambers. he liked closed chamber heads for a number of reasons
1. valve shrouding is really not that bad on the later(68-69) heads
2. you take have a smaller dome piston or flat top and it doesn't screw up the flame travel
3. the tighter and smaller combustion chamber gives a better and quicker fuel burn off which means you can usually run more spark advance.
4.port thses heads out and you'll have great flow.

Here is another idea.
Use an open chamber head and then have them angle milled to raise your comp. ratio and improve head flow.