Open Chamber Heads vs Closed Chamber Heads....

Prefer Open Chamber or Closed Chamber for Racing

  • Open Chamber

    Votes: 5 17.2%

  • Closed Chamber

    Votes: 24 82.8%
  • Total voters
    29
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yellow rose said:
None of those are actually closed chambered heads. And, the trend is getting the chambers even softer.
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I agree if we're talking power adder motors, but high output NA will have closed chambers. Here is a Chevy RO7 cup car head probably one of the best NA motor head made in the last 20 years. Looks like a tight compact chamber to me.

cTmxF56.jpg
 
The problem with trying to acheive quench with a dome piston and an open chamber is that none of the chambers are cast the same height. The 596 heads off my 360 are about .020 different in height from one chamber to another, and can be dipped over .015 from one side of the chamber to the other.
 
skrews said:
I agree if we're talking power adder motors, but high output NA will have closed chambers. Here is a Chevy RO7 cup car head probably one of the best NA motor head made in the last 20 years. Looks like a tight compact chamber to me.

View attachment 1715588333
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The real issue is the definition of what a “closed” and “open” chamber really is. Most chambers are a cross breed of both.

I tried to find a picture of what I consider a true closed chamber BBC head, but I couldn’t.

When you look at the chamber of the RO7 head, you see the spark plug side is laid back and relatively short.

The intake side is very shallow and almost no chamber wall.

On what I consider a true closed chamber, you’d have both sides of the chamber vertical and very close to the valves.

I can tell you the number one flow and power killer is a “hard” “closed” chamber.

It seems we are quibbling over various versions of “soft” “closed” chambers. I haven’t seen what I consider a real closed chamber in 30 years, unless it’s some old thing.

The worst Chrysler chamber I’ve dealt with is the W5 chamber. That is considered a closed chamber and it takes a ton of work to be respectable. Removing the outside quench pad pissed it off. I suggest Chrysler knew this, but the sniveling for a “closed” chamber to get quench (which I have said many times is overrated) and they gave up power for quench.
 
All i know is that i prefer closed chamber mopar heads, and open chamber bbc heads. The original closed chamber big chevy heads were awful.
 
skrews said:
The problem with trying to acheive quench with a dome piston and an open chamber is that none of the chambers are cast the same height. The 596 heads off my 360 are about .020 different in height from one chamber to another, and can be dipped over .015 from one side of the chamber to the other.
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True. I have my chambers within .005 on all 8 holes and .5 cc’s. I’ll be at 11.77:1 with about .048 quench.

Just did a pump gas 12.0:1 open chamber deal. I’ll finish the tune up a week from tomorrow. Pretty low dome. I forget the quench but it wasn’t much.
 
Plus the twisted wedge design, like the Chevy head above and the aftermarket Ford head, puts the valve close to the port. Quick mixture in and spent gasses out.
 
Yeah the old 396 bath tub chamber is the true definition of a closed chamber. I tend to consider anything with a decent size dual quench pad to be a closed chamber such as the magnum. Heads like the SB 302 or BB 915 not really as they only have one closed pad, I put the W5 in that group too.
 
yellow rose said:
The real issue is the definition of what a “closed” and “open” chamber really is. Most chambers are a cross breed of both.

I tried to find a picture of what I consider a true closed chamber BBC head, but I couldn’t.

When you look at the chamber of the RO7 head, you see the spark plug side is laid back and relatively short.

The intake side is very shallow and almost no chamber wall.

On what I consider a true closed chamber, you’d have both sides of the chamber vertical and very close to the valves.

I can tell you the number one flow and power killer is a “hard” “closed” chamber.

It seems we are quibbling over various versions of “soft” “closed” chambers. I haven’t seen what I consider a real closed chamber in 30 years, unless it’s some old thing.

The worst Chrysler chamber I’ve dealt with is the W5 chamber. That is considered a closed chamber and it takes a ton of work to be respectable. Removing the outside quench pad pissed it off. I suggest Chrysler knew this, but the sniveling for a “closed” chamber to get quench (which I have said many times is overrated) and they gave up power for quench.
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You ain't lookin real hard.

BBC CLOSED CHAMBER.jpg
 
Those old closed chamber big Chevy heads flow better than you think they do. Were the chambers not turned, they would suck. They don't suck.
 
RustyRatRod said:
Those old closed chamber big Chevy heads flow better than you think they do. Were the chambers not turned, they would suck. They don't suck.
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Yep, my Chevy friend showed me them years ago at our porting party. lol
We had money for beer, but not gas. We ported heads. lol and built motors.
 
skrews said:
Yeah the old 396 bath tub chamber is the true definition of a closed chamber. I tend to consider anything with a decent size dual quench pad to be a closed chamber such as the magnum. Heads like the SB 302 or BB 915 not really as they only have one closed pad, I put the W5 in that group too.
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LOL...that was the EXACT head I was trying to get a picture of. Couldn’t find one.
 
RustyRatRod said:
So all of yall who come out in droves thinkin quench is the greatest thing in the world now think open chambers are the cat's.

Damn
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41 minutes in between your dump post and this post that must have been one hell of a wrestling match...
 
RustyRatRod said:
Those old closed chamber big Chevy heads flow better than you think they do. Were the chambers not turned, they would suck. They don't suck.
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Yes actually they do suck in comparison to 781's. Back in 2002 I built 2 454's at the same time. Both engines had similar camshafts (SFT) and same compression (10.5). One 454 had the closed chamber heads and the other had '781's . Game plan was to dyno both engines on the same day and he would pick the best one of the two, install it in his Chevelle and sell the other. This was before I had a dyno so we travelled a little ways to a shop that only tested engines and built headers.

The closed chamber head 454 made 560 hp 540 tq and was VERY sensitive to timing changes and coolant temp. It would drop serious HP/TQ above 160F water and it was very prone to detonation. The open chamber '781 headed 454 made 540HP 560TQ and didn't care if the timing was 34, or 40 or 160F or 200F it always made the same power. It also had a much smoother power curve. My customer kept the 540HP 454 and went high 11's @ 118MPH consistently-the other he sold. I can't really describe it but the closed chamber 454 was really finicky with a jagged spiky power curve. This was before averages were displayed at the bottom of the dyno sheets but IIRC the averages were about 20 points in favour of the '781 headed 454. Those closed chamber heads suck if you leave them as is. J.Rob
 
RAMM said:
Yes actually they do suck in comparison to 781's. Back in 2002 I built 2 454's at the same time. Both engines had similar camshafts (SFT) and same compression (10.5). One 454 had the closed chamber heads and the other had '781's . Game plan was to dyno both engines on the same day and he would pick the best one of the two, install it in his Chevelle and sell the other. This was before I had a dyno so we travelled a little ways to a shop that only tested engines and built headers.

The closed chamber head 454 made 560 hp 540 tq and was VERY sensitive to timing changes and coolant temp. It would drop serious HP/TQ above 160F water and it was very prone to detonation. The open chamber '781 headed 454 made 540HP 560TQ and didn't care if the timing was 34, or 40 or 160F or 200F it always made the same power. It also had a much smoother power curve. My customer kept the 540HP 454 and went high 11's @ 118MPH consistently-the other he sold. I can't really describe it but the closed chamber 454 was really finicky with a jagged spiky power curve. This was before averages were displayed at the bottom of the dyno sheets but IIRC the averages were about 20 points in favour of the '781 headed 454. Those closed chamber heads suck if you leave them as is. J.Rob
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I'm sure you're right. I've seen plenty of fast cars run them. Like everything, they could have been faster.
 
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