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"Air Gap" Intake Manifold

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Old 10-05-2012, 09:52 PM   #1
65tripleblack
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Default "Air Gap" Intake Manifold

What is its purpose? Why would an Edelbrock RPM Air Gap be better/worse than an Edelbrock RPM?
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Old 10-05-2012, 10:09 PM   #2
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What is its purpose? Why would an Edelbrock RPM Air Gap be better/worse than an Edelbrock RPM?
Edelbrock claims the Air Gap provides a cooler inlet charge. Hot Rod magazine did a test on this and found that the Air Gap only saw a 2-3 hp difference above 5600 rpm on the dyno. They did note that there wasnt a lot of heat built up while running on the dyno. I guess it could make a difference in the real world.
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Old 10-06-2012, 09:16 AM   #3
Matt Gruber
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Purpose is to make $$$.
IMO it is much worse than the RPM. Hard to drive/warmup below 60F. And it connects the high and low plane so it will draw in lots of exhaust at low rpm during overlap, with a performance cam. it might run awful at low rpm. Might not, it depends on the whole combo.
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Old 10-06-2012, 04:45 PM   #4
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My motor is an Edelbrock Performer 350 which includes the Performer Air Gap intake (among many other things.)

I believe another of the benefits of the air gap design is a cooler carb, reducing vapor lock issues. If so, it seems to work as we've run well in some very hot temps.
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Old 10-06-2012, 07:29 PM   #5
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I heard it's difficult to keep the area underneath (air gap) clean. I've never owned one, so it's just what I've read.
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Old 10-06-2012, 09:10 PM   #6
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I heard it's difficult to keep the area underneath (air gap) clean. I've never owned one, so it's just what I've read.
Not bad from my experience, but might be if you have any leaks from anything. I get bugs in mine sometimes but the air hose takes care of them.
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Old 10-07-2012, 06:45 AM   #7
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My motor is an Edelbrock Performer 350 which includes the Performer Air Gap intake (among many other things.)

I believe another of the benefits of the air gap design is a cooler carb, reducing vapor lock issues. If so, it seems to work as we've run well in some very hot temps.
That one does NOT have a cut down divider. So it will not narrow the power band like the RPM can when used with a higher overlap cam. To keep any carb below the boiling point of gas, i've found that a $3.50 fan and duct works best. The carb can boil about 1 hr after shut down, hood closed. So unless you re-start it then, you might not notice it. It could be the air gap helps, in that case
Fall is here. How does the airgap work out on a cold start, say 45F? Can you still drive off normally with a cold carb? How is the MPG? I find my mpg drops a lot on cold starts. And i sure don't sit there waiting for it to warm up. That would be ZERO mpg. If i still lived in NJ i'd want the heat riser connected. Winter is right around the corner. So it depends on where you live, and how you drive. What intake will work best depends on many factors.

Last edited by Matt Gruber; 10-07-2012 at 09:35 AM.
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Old 10-07-2012, 05:19 PM   #8
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That one does NOT have a cut down divider. So it will not narrow the power band like the RPM can when used with a higher overlap cam. To keep any carb below the boiling point of gas, i've found that a $3.50 fan and duct works best. The carb can boil about 1 hr after shut down, hood closed. So unless you re-start it then, you might not notice it. It could be the air gap helps, in that case
Fall is here. How does the airgap work out on a cold start, say 45F? Can you still drive off normally with a cold carb? How is the MPG? I find my mpg drops a lot on cold starts. And i sure don't sit there waiting for it to warm up. That would be ZERO mpg. If i still lived in NJ i'd want the heat riser connected. Winter is right around the corner. So it depends on where you live, and how you drive. What intake will work best depends on many factors.
Yes, I guess the Air Gap Performer design differs from the RPM. My Edelbrock 350 had the polished option, so cleaning it really isn't too much of an issue. I too use air to blow out and maintain the shine with a little Mother's Billet polish/cleaner.

As for cold temp issues, I don't really have any. It won't see winter but it does see some cold weather driving (for example today the high was just 46F.) Fortunately it sees a lot more warm temps than cold, so overall the design suits my requirements just fine.
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Old 10-08-2012, 12:21 PM   #9
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What is its purpose? Why would an Edelbrock RPM Air Gap be better/worse than an Edelbrock RPM?
Not sure......the manifold...Air gap or not is huge heat sink and the water passes through the front....eventually it will heat up....

The runners on both manifolds are near identical....
One benefit of the air gap is it is easy to hide a pcv in the valley....and things like wires and sensor lines for mechanical gauges can be routed through it for a clean look.....but is that worth $75?

A much greater benefit is had by insulating the carb from the manifold...
and keeping engine temps around 175 degrees....

Another thing to keep in mind is that an open spacer absolutely destroys these intakes.....run four hole spacers only on these....

Jebby
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Old 10-08-2012, 12:37 PM   #10
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Not sure......the manifold...Air gap or not is huge heat sink and the water passes through the front....eventually it will heat up....

The runners on both manifolds are near identical....
One benefit of the air gap is it is easy to hide a pcv in the valley....and things like wires and sensor lines for mechanical gauges can be routed through it for a clean look.....but is that worth $75?

A much greater benefit is had by insulating the carb from the manifold...
and keeping engine temps around 175 degrees....

Another thing to keep in mind is that an open spacer absolutely destroys these intakes.....run four hole spacers only on these....

Jebby
Jebby
Thermal characteristics are what I had in mind when I made the OP. Especially how it relates to coolant temp and thermostat selection.

Think of situations where an engine designer has the option of keeping oil temp fully independent of coolant temp.
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Old 10-08-2012, 01:15 PM   #11
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Thermal characteristics are what I had in mind when I made the OP. Especially how it relates to coolant temp and thermostat selection.

Imagine a situation where an engine designer has the option of keeping oil temp fully independent of coolant temp.
I understand....but it makes no differance because both manifolds will heat sink equally.....especially with the aluminum factor.....they bolted
to the hot heads...and both get splashed from underneith....

The only way to separated the two is to have the manifold be two piece.....have a "pan" made of low thermal phenolic...then a aluminum
"manifold" bolted to that....

Jebby
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