What is the differnce between open and closed chamber heads and which are better ??

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69 Camaro RS, 355ci, 72 gm casting heads,mild cam, Preformer rpm intake, edelbrock 600 carb, 350 turbo w/ shift kit 2500 stall, 12 bolt 4.56 posi..

Open chamber heads have a numerically higher 'cc' volume than closed chamber heads do.
Open chamber heads, the chamber looks sort of heart shaped and the intake ports are usually oval shaped.

Closed chamber heads, the chamber looks sort of peanut shaped and the intake ports are usually rectangular shaped.

Which are better?
My opinion, I'd say open chambers for the street. They will have better fuel economy and good low to mid range power.
Closed chambers for the strip. They will perform better at the higher rpm range.



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Ricky
68/RS on Blocks...

Open and closed chamber is determined by the shape and design of the chamber in the head as described above. However, the rectangular or oval port (as looking at the intake port itself) is the major factor as to determining which head to use. Every open chamber head I've owned has been a rectangular port, but they come with oval ports also. Most of the closed chamber heads I've seen were oval ports but they made rectangular versions also.

MOST street cars will e.t. better with a good set of oval ports (especially heavy cars) as they make more low and mid-range torque when properly set up. They generally don't make as much peak hp upstairs although there are exceptions here also. It's been a long lived debate on oval versus rectangular, but the fact is there are several 10 second oval port headed Chevelles on the sister Chevelle board. You need to determine what the usable rpm range is and what you're trying to accomplish. The open versus closed chamber isn't as critical to me (just make sure you get the matching pistons for whichever way you go) as the oval or rectangular port.

Jody

A couple more points.
1- Open chamber heads can use either closed or open chamber pistons.Closed chamber heads can only use closed chamber pistons.
2- Open chamber heads also have more room around the valves because of the larger cc combustion chamber.Like stated by the others you need to decide what you want the engine to do.I had a 427 bored .060 over with rectangle port haeds in my 73 z28 years ago and it had all kinds of bottom end on pump gas.Both are good heads,hope this helps.

Brian.

71 camaro 540 ci,turbo 400,cal tracs,tublar a-arms.

An advantage of the closed chamber heads is that you can get a good compression ratio with flat top pistons, eliminating the need for a dome. But frankly, if they were all that good, they'd still make them. To run big valves in them you have to unshroud the valve. Many a good head has been wasted by someone cutting too deep and hitting the water jacket.

I run 049 oval-port open chamber heads on my 502, they work good.

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67RS STREET CAR, 502 PUMPGAS, HYD. ROLLER, TH350 w/ATI 10" 12-BOLT w/373 - 10.92@125.2 ON MOTOR, ET-STREETs w/MUFFLERS

And to make things more confusing GM/Edelbrock make "roval" intake port heads w/ semi open chambers out of aluminum. They are about 290 cc intake port volume and are sized like ovals but shaped like short "rectangular" ports at the manifold face.
There are also two types of oval port heads. First is standard "large" ovals that came on everything and second small oval port heads that have the nickname" peanut port" because they are sized not much bigger then a healthy h.p. small block head. They generally came on trucks!!! Something like 200+cc vs 250+cc for the large oval port heads vs 290cc up to 325cc for rectangular port H.P.heads.

Only the rectangular heads were made stock in aluminum up to th new "roval" heads. Hope this isn't too confusing. pdq67

PS., And to make matters worse, open chambered heads are made in two configurations. Standard and smog or laid back square at the exhaust valve for even more open chamber. The closed chambered heads were more "bathtub" shaped then bean shaped IMHO.

And its been proved by many people that a good set of oval port big valved heads are dandy for the street!! You can also buy Merlin cast-iron oval port heads that are very good for street applications in the up to 500 cubic inch engine sizes. Again IMHO and not trying to pick a fight!!

In a heavy car oval port heads work fine. But with a 427or bigger in a light nose heavy car like a camaro you have a real problem with traction. The Chevelle guys make them work fine but a Chevelle is a bunch heavier and not nearly as nose heavy. On most of my race cars I spent more time trying to kill the low speed torque than trying to make HP. If you are running a 396 don't even consider big ports unless it is a real race car they run much better with ovals. I hope I am not starting a fight but I have run them both on just about every BB car I have owned and my expereinces have led me to believe my statements to be correct.

Well thanks for all the info guys ... the reason i was asking is i was looking at a set of 461 gm heads for a 355 and i have the option of open or closed chamber heads and was wondering which was better. The car is a street/strip car.

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69 Camaro RS, 355ci, 72 gm casting heads,mild cam, Preformer rpm intake, edelbrock 600 carb, 350 turbo w/ shift kit 2500 stall, 12 bolt 4.56 posi..

Open and closed chambers refers to big block heads. There are different cc chamber sizes for small blocks but they are not referred to as open chamber/closed chamber. Who is trying to sell you some small block heads with that option?

Jody

Jody's right. The guys who responded were assuming you were talking big block heads. Closed/open chamber and oval/rectangular port are big block issues. All SBC's are basically a closed chamber design of SLIGHTLY varying size. Someone's feeding you a line, or has their terminology slightly wadded up. If you're looking for low-buck options, I'd look at Vortecs ($450 or so - requires about $225 worth of intake and rockers, though), or I'd find someone who knows better what they're talking about to get some ported early heads from. Or spend the big bucks and get a set of AFR 190's. But I wouldn't waste my money on someone who's trying to sell you open vs. closed chamber small block heads.

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Huck
355 SBC powered '87 Chrysler Conquest TSi - 10.3:1, Vortec heads, XE 268H cam, HEI, eq. length shorties, Performer RPM intake, 750 Edelbrock (1407), T-5 and 3.54:1 posi indep. rear

The dude is technically right because the -461 head IS the only closed chambered SB head!! All the others are opened up below the sparkplug.

BUT, me thinks somebody might be trying to dazzle you w/ B.S. to bring this up as a selling point.

If you can get them worth the money AND they are FRESH and crack-free, then get them because they are good stock heads but as said earlier, the new aftermarket heads are better value, plus stronger and NEW. IMHO. pdq67