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What are the pro's and cons of them... I have a chance to pick up a set of Large Oval port closed chamber heads # 3931063. they have been seriosly worked over and are cut for the big valves . Are they worth getting? or are the open chamber heads superior in the performance quest?
A little help here....Infomaniac?
Bryan
anyone....anyone.... Bueler........
I had read that the close chamber shrouds the valves too much and kills some of the flow.
Watch out for piston to chamber interference, valve to piston clearence, good way to raise compression without changing pistons. B472's statement is valid also. If their cheap and you don't mind turnin wrenches, what the hell may be a good combo for you.
My .02
KC
Open chambers make more HP, a fact. Most people making any serious HP with BBC's run open chambers, as the valves are unshrouded and are able to flow just a little better.
ARE THERE ANY DRAWBACKS TO RUNNING OPEN CHAMBER HEADS?
DO THEY COME IN BOTH OVAL AND RECTANGULAR CONFIGURATIONS? GENERALLY DO CAST IRON OR ALUMINUM OPEN CHAMBER BREATHE EASIER? WOULD ONE BE BETTER THAN ANOTHER USING A BLOWER ON MY JET BOAT?
I'M WONDERING WHAT WOULD MAKE MY 502 GEN VI BLOCK REALLY PUT-OUT!. LOTS OF QUESTIONS, JUST SO MANY DOLLARS TO SPEND. THANKS MUCH...BILL.
Open chamber heads breath better due to valve unshrouding as mentioned above. Cast iron heads retain heat and heat is HP, but aluminum heads offer lightweight and repairability. I've heard the round port heads are actually better for lower rpm and throttle response. I think I would go the rectangle port heads for any blower use if given a choice.
Originally posted by THE BOSTON SIDEWINDER
ARE THERE ANY DRAWBACKS TO RUNNING OPEN CHAMBER HEADS?
DO THEY COME IN BOTH OVAL AND RECTANGULAR CONFIGURATIONS? GENERALLY DO CAST IRON OR ALUMINUM OPEN CHAMBER BREATHE EASIER? WOULD ONE BE BETTER THAN ANOTHER USING A BLOWER ON MY JET BOAT?
I'M WONDERING WHAT WOULD MAKE MY 502 GEN VI BLOCK REALLY PUT-OUT!. LOTS OF QUESTIONS, JUST SO MANY DOLLARS TO SPEND. THANKS MUCH...BILL.
BSW You asked a lot but didn't say how you'd be using your setup, intended use is as important to part selection as type of boat. Determining how you intend to use it will help you decide on how to spend wisely instead of just throwing cubic dollars at and then being unhappy with the outcome, as the engine doesnt quite match your needs. Are you going to put a full race blown deal in a multi use boat that you want to live for more than a weekend before you freshen it up? How do you use your boat? Do you run it at 5000 RPM's for extended periods of time like 30 minutes to an hour? OR would you want to be able to run it up to 7500 RPM for short bursts? How about drivability & maintenance & fuel consumption?
I prefer open Chamber heads, as they make more power than a closed chamber as long as compression is the real close & iron builds more heat, which is HP. However I feel aluminum is superior since it will let you also run more timing, which is also HP, they are lighter & more easily repairable than iron so they get an advantage in my book. They do come in both oval & rectangle & type of material makes no difference how they breathe. Depending on intended use you need to choose your valves carefully or you'll be building it again.
There's lots to think about
SORRY FOR THE LASK OF INFO. I USE IT RECREATIONALLY ON WEEKENDS, ALMOST NEVER OVER 5.5K RPMS, AND ONLY UP TO 6K OR SO IF I ACCIDENTY LOOSE SUCTION FROM A WAVE, NEVER TO 7.5K RPMS. DRIVEABILITY IS JUST HORSING AROUND BOSTON HARBOR, AND REBUILDING IT EVERY TIME OUT WOULD BE TOO KILLER AN ENGINE FOR ME...BILL.
There is only a benefit to open chamber heads when you really start lifting the valves high. If you have a camshaft with less than .540 inches of valve lift there is no difference in performance.
I have done some research on the Edelbrock BB heads. The Edelbrock Marine head and Performer 454-O head have semi-open chambers that hold 110 cc's (these head castings are used on the 502/502 crate engine). The Edelbrock Performer High Compression 454-O head has a closed chamber that holds only 100 cc's. These Edelbrock heads look very similar to the closed chamber heads of a 1960's and semi-open chamber heads of the early 1970's built by Chevrolet.
If you believe that Edelbrock sells a well engineered product, you would have to conclude that a close chamber head must work pretty well.
Dennis Moore