> Ok - I feel like an idiot at this point. The intake that is sitting in the > shop is an Edelbrock Performer - Not an Edelbrock Performer RPM Air Gap. > My question is this - should I send it back and get the RPM Air Gap or stick > with just the standard Performer?
The RPM Air Gap is a much better intake on a modified engine but is considerably taller.
> The cost difference is only about $120. Any clue as to the HP difference > between these two?
See attached dyno results below. If you plot the data, you'll notice the RPM Air Gap is better across the tested rev range which is more important than just peak numbers. Also, notice the standard Performer was only tested with a 1" spacer as the dyno carb fuel log wouldn't clear otherwise. Note that it really responded to the 1" HVH spacer.
> I know one of the comments from previous posts was asking about the air > screen. If I decide to leave the screen in place, will the RPM Air Gap > version fit with a dropped air cleaner?
No.
> I believe Dan mentioned that if I went with the standard Performer that it > would need some work in the plenum area. How much would this help if I > decide to go with the standard Performer
On a Ford aluminum dual plane, it helped a bunch on the nearly 500 HP 408C it was tested on. In those tests, the ported Ford aluminum dual plane made 31 HP and 23 ft-lbs more than an unported Blue Thunder. The ported Blue Thunder pulled better numbers on the flow bench (attached to a cylinder head) and would have likely made better power but was not tested. We did test the ported Blue Thunder this weekend on Mike McDougal's 393C and it made 411 HP at the rear wheels through the mufflers and small air cleaner so the porting worked.
> and what exactly needs to be done?
The problem with older dual planes is that half of the runners often flow much worse than the other half when bolted to a cylinder head. If you bring up the poor runners to match the good runners, it really pays off. Note that we really aren't porting the runners. What we do is cut down the plenum divider and radius the port entry in the plenum to aid flow into the poorer flowing ports. This needs to be done on a flow bench with a cylinder head attached and a carb in place. IIRC, Dave McLain charged Mike McDougal $150 to port his Blue Thunder intake (correct me if I'm wrong Mike). If you are interested in keeping a stock engine screen, you may want to consider sending me your intake and we can port it on the flow bench and dyno it in ported and unported form. I believe I have a spare Performer here so if you want to hang on to the intake and drive the car, we can port my spare intake and exchange them after the testing is completed. If you want to ditch the engine screen, go with the Air Gap intake. If you look at the plenum of the RPM Air Gap, you'll see the divider is already cut down and the runners are reasonably well equalized.
Dan Jones
Performer with 4 Hole 1 Inch Spacer 950 HP dyno carb, Pantera GTS headers and Magnaflow mufflers. Note: Intake is actually the earlier F-351 4V version but appears identical to the current Performer. The Perfomrer required a spacer for throttle clearance so was tested only with 1" spacers. Baseline for Edelbrock Performer intake was with a 4 hole 1 inch spacer which was needed to allow clearance for fuel log. Good solid pull and for whatever reason the engine didn't seem to mind the 1 inch 4 hole on this dual plane. Going to try the HVH spacer next.
Performer with HVH Spacer 950 HP dyno carb, Pantera GTS headers and Magnaflow mufflers. HVH was also better on the Edelbrock Performer but not as drastic as with the factory iron piece. Performer is better than factory cast iron intake or so it seems on this engine.
Performer RPM Air Gap 2V 950 HP dyno carb, Pantera GTS headers and Magnaflow mufflers. Baseline for Performer RPM airgap intake. Like many of the intakes designed for 2V heads, the RPM Air Gap will fit either 2V or 4V heads. Running with no spacer. Going to try the 4 hole 1 inch and HVH spacers next. Good solid pull with good numbers.
Performer RPM Air Gap with HVH 950 HP dyno carb, Pantera GTS headers and Magnaflow mufflers. HVH spacer seems to run about in the middle of the bare intake or 4 hole 1 inch. Good all around performance making over 380HP and torque.
Performer RPM Air Gap with 4 hole 1 Inch 950 HP dyno carb, Pantera GTS headers and Magnaflow mufflers. Good pull and engine picked up about 5 horsepower and about 10lbs/ft with 4 hole. A good swap and about the best all around combo for these heads etc.
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