Edelbrock Vortec RPM or Air RPM intake - Hot Rod Forum : Hotrodders Bulletin Board
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Old 07-18-2010, 08:39 PM
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Edelbrock Vortec RPM or Air RPM intake

Which would be the better intake: 1. Edelbrock RPM or 2. Edelbrock RPM Air Gap? or best recommended vortec intake for the following motor:

350ci
9.5 C/R flat top pistons
stock vortec heads 64cc, 1.94/1.5 valves
cam 224/224 @ .050 duration, adv dur 290, .465/.465 lift, idle to 5,500 RPM
600 cfm holley
3.73 gears
4-speed

THanks.

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Old 07-18-2010, 09:10 PM
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I haven't used an Air Gap yet and maybe never will if I don't build any more motors, but it makes sense to me that if you can separate the hot oil splashed onto the bottom of the manifold from the intake mixture, you would get a denser charge into the heads. Anyway, my vote is RPM Air Gap. You're already penalized for driving in cold weather with the L31 heads which have no heat crossover, so I don't see where it will matter much if you have cold air running under the intake. Just let the motor warm up to operating temp in colder weather and the thermostat will handle it from there.
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Old 07-18-2010, 09:24 PM
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Thanks for the info and recommendation!
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Old 07-18-2010, 10:02 PM
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Whats it going in?
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Old 07-18-2010, 10:15 PM
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Manifold?

Step up and pay the extra for the air gap dual plane. Well worth it. With a any cam and head upgrade this manifold works. Edelbrock rocks! Great torque in 400 or larger SBC's
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Old 07-18-2010, 10:30 PM
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Icing is a myth. On the road a properly set choke with high idle , the charge will not be effected. 440's have been air gaps since there were 440's. Factory 440 don't have icing problems.

Down side, you won't see much power improvement because you separated the hot oil from the runners...Hot oil still hits the base of the intake unit, and aluminum transfers heat nicely. 440's don't even have the one peice botttom, 440 have a separate pan. No oil hits there intakes.

The Performer/ and RPM air gap runners have been changed, well as plenum volume, and texture. These alterations give the fuel more volume with a straighter shot to the chamber, while maitaining mix velocity. The EPS performer , and air gap performer make about 10 more hp on a dyno . Attached or not becuase they improved the runners.
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Old 07-18-2010, 10:57 PM
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So what your saying is the air gap under the intake is BS? I find it hard to believe the Edelbrock would design it that way for no reason, Improved runners or not. That's why pontiac and mopar designed the separate valley pan's, to keep hot oil off the bottom of the intake.
And as far as the aluminum heat transfer, thats why they make heat separator gasket's for carburetors.
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Old 07-18-2010, 11:25 PM
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The manifolds are one peice covering the valley. The temp of the outer air gap bottom is the same temp, as the runner going into the head.

If you can lazer temp gun the intake at the different places. Climb out on the fender with the hood off/open, have a buddy drive and take some readings. Idle won't have the cooling fuel mix flowing. Its action time. Might want to take a timming light out on the limb while you are riding the fender. At 35mph under the hood see if that vacuum advance can is hanging the curve high. Do this fender ride at night so you can see the timing mark.

Mopar made more power because they had long 6.123 rods, better bore x stroke ratio , and rod x stroke ratio, and strong shaft rocker geometry. Held down by the worst head selection for flow.

Last edited by spinn; 07-18-2010 at 11:32 PM.
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Old 07-19-2010, 10:25 AM
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I didn't like the air gap on my 454. It was slow to warm up and things always seem to fall into the "air gap" area under the carb.

Had slow warms up issues if temps dropped below 55 or 60F. The carb would stumble right off idle for 15 to 20 minutes, until the carb got warm enough to run right. I could richen up the carb to over come the stumble issue when cold but then would run very rich once the carb and intake warmed up.

I ended up selling the air gap to a guy on this site and fully disclosed my issue with the intake. I now use a regular style intake with restrictors in the exhaust cross over ports. much happier now. Carbs need heat to vaporize the fuel properly.

I say, get a regular RPM intake and forget the air gap.
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