Edelbrock Performer 289 vs. RPM Air-Gap - Vintage Mustang Forums
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post #1 of 27 (permalink) Old 01-12-2018, 12:58 PM Thread Starter
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Edelbrock Performer 289 vs. RPM Air-Gap

My son did back to back dyno pulls on a 347 they just built for a customer with two different intakes. The RPM Air-Gap gave the engine a 28 HP gain up top over the 289 Performer. He said he got another 5 or 6 HP out of it later with additional tuning.

The customer is concerned with hood clearance which is why they were looking at the 289 intake. After they shared the results the customer decided to go with the Air-Gap. Said he would figure out the clearance issue.
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1966 Fastback C code, T5z transmission, 8.8 4.10 Trac-Lock, AFR 165 heads, PRC Tuned Holley XP carb, RPM Air Gap intake, Comp Cams XE268H. First car...restored it with my dad in 1988.
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post #2 of 27 (permalink) Old 01-12-2018, 01:26 PM
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Interesting results and thanks for sharing your real world info. I just finished surfing the web about intakes on 347's and read that the power diff between those 2 intakes was in the 5-10 hp range. One possible reason for the large difference in your case was maybe the Performer didn't fit the gasket or head ports as well as the air-gap? The air-gap does have 10% larger port volume and a more direct shot to the head than the performer. From my fuzzy memory the air gap is 5/8 or 3/4 taller than the performer. So all that will help with the upper RPM power.
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post #3 of 27 (permalink) Old 01-12-2018, 01:46 PM Thread Starter
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Interesting results and thanks for sharing your real world info. I just finished surfing the web about intakes on 347's and read that the power diff between those 2 intakes was in the 5-10 hp range. One possible reason for the large difference in your case was maybe the Performer didn't fit the gasket or head ports as well as the air-gap? The air-gap does have 10% larger port volume and a more direct shot to the head than the performer. From my fuzzy memory the air gap is 5/8 or 3/4 taller than the performer. So all that will help with the upper RPM power.
I agree that there is probably a little more in play because 28hp is huge difference. The engine (cam) was designed for the Air-Gap. Not sure if with a different cam would the difference not be as great.

With that said, when I replaced my Stealth with the Air-Gap, my butt dyno reported a significant difference.


1966 Fastback C code, T5z transmission, 8.8 4.10 Trac-Lock, AFR 165 heads, PRC Tuned Holley XP carb, RPM Air Gap intake, Comp Cams XE268H. First car...restored it with my dad in 1988.
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post #4 of 27 (permalink) Old 01-12-2018, 01:49 PM
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We're running an RPM Air Gap on our 68. We had to switch to a low profile air cleaner to be able to close the hood.
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post #5 of 27 (permalink) Old 01-12-2018, 01:57 PM
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testing i have done between the air gap and rpm biggest difference was the price
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post #6 of 27 (permalink) Old 01-12-2018, 02:04 PM
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Have tested the stealth against rpm, torker original warmed over a bit and torker II on my 460 in my dualy with ported heads and mild cam. The stealth did the worst conclusion it would do best on a big stroker build based on port cross section sizes.
the orig torker and rpm close to the same the torker II kicked butt on all of them
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post #7 of 27 (permalink) Old 01-12-2018, 02:19 PM
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Quote:
Originally Posted by Fair Oaks Mustang View Post

The customer is concerned with hood clearance which is why they were looking at the 289 intake. After they shared the results the customer decided to go with the Air-Gap. Said he would figure out the clearance issue.
I have an Air Gap RMP on a 302 in my '66 Mustang using a dropped base 13X3 inch air cleaner. Its close but does not interfere with the hood.

'66 Coupe: GT40 5.0: 670 Holley & Edelbrock RPM AirGap: JBA shorties: AOD w/TCI shiftkit: Granada Disks: R&P steering: 3.55 Currie
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post #8 of 27 (permalink) Old 01-12-2018, 02:23 PM
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It's my understanding that the performance difference between a Performer RPM and Performer RPM Air Gap is nominal, while the non-Air Gap RPM version is shorter and can therefore buy you some hood clearance. That's what I have and clearance is not an issue.

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post #9 of 27 (permalink) Old 01-12-2018, 03:10 PM
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What year mustang is it going into? I've seen guys use an air gap intake on 351w's in 67/68 mustangs with the stock hood. I can't foresee why there would be an issue in a 65/66 with a 302 based motor, which is about 1.5 shorter than a 351w, unless he used a carburetor spacer. If you're set on using the air gap intake I'd recommend some adjustable motor mounts like the Ron Morris ones. They will allow you to adjust the height of the engine so if you did have a clearance (height) issue, it should fix that. If that solely didn't fix it you could also use a drop base or low profile air cleaner. Either or should fix the issue if it arose, using both I would think would have no issues whatsoever.
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post #10 of 27 (permalink) Old 01-12-2018, 03:44 PM Thread Starter
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Originally Posted by MUSTANG65FBK View Post
What year mustang is it going into? I've seen guys use an air gap intake on 351w's in 67/68 mustangs with the stock hood. I can't foresee why there would be an issue in a 65/66 with a 302 based motor, which is about 1.5 shorter than a 351w, unless he used a carburetor spacer. If you're set on using the air gap intake I'd recommend some adjustable motor mounts like the Ron Morris ones. They will allow you to adjust the height of the engine so if you did have a clearance (height) issue, it should fix that. If that solely didn't fix it you could also use a drop base or low profile air cleaner. Either or should fix the issue if it arose, using both I would think would have no issues whatsoever.
Not sure what it is going into. My son works in a machine shop building crate motors...being built for one of their customers. Personally I have the air gap on my 66 with a stock hood. It is close, but it fits.


1966 Fastback C code, T5z transmission, 8.8 4.10 Trac-Lock, AFR 165 heads, PRC Tuned Holley XP carb, RPM Air Gap intake, Comp Cams XE268H. First car...restored it with my dad in 1988.
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post #11 of 27 (permalink) Old 01-12-2018, 04:10 PM
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If they compared the regular Performer (and not the RPM) version against the Performer RPM Air Gap I could see that kind of difference happening. The OP wrote 289 Performer, not Performer RPM.

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post #12 of 27 (permalink) Old 01-12-2018, 04:12 PM
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Originally Posted by gregb View Post
If they compared the regular Performer (and not the RPM) version against the Performer RPM Air Gap I could see that kind of difference happening. The OP wrote 289 Performer, not Performer RPM.
Right. Conventional wisdom says that the regular RPM is very similar to the RPM Air Gap as far as performance goes. The only reason the regular RPM is in the conversation is for hood clearance.

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post #13 of 27 (permalink) Old 01-12-2018, 05:05 PM Thread Starter
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Originally Posted by gregb View Post
If they compared the regular Performer (and not the RPM) version against the Performer RPM Air Gap I could see that kind of difference happening. The OP wrote 289 Performer, not Performer RPM.


Correct, it was a 289 performer. From what I understand, it is basically an aluminum version of a stock manifold. (I could be wrong)


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1966 Fastback C code, T5z transmission, 8.8 4.10 Trac-Lock, AFR 165 heads, PRC Tuned Holley XP carb, RPM Air Gap intake, Comp Cams XE268H. First car...restored it with my dad in 1988.
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post #14 of 27 (permalink) Old 01-12-2018, 05:09 PM
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I agree with Greg, sounds like they tested the regular Edelbrock Performer which is only good for completely stock engines. Going to the Edelbrock Performer RPM or Air Gap on a 347ci would should have shown a huge performance increase so sounds about right. The RPM and Air Gap seem to flow about the same from most stuff I have read. Man look at that Torque, can't see the range but looks like a fun car to drive.

1967 Mustang Convertible, 289-4v, C4, Edelbrock Performer Intake, Mild Cam.
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post #15 of 27 (permalink) Old 01-12-2018, 05:29 PM
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any more specs. on that engine build ?

'65 A-code coupe, T-10 4-speed, 8" 3.25 limited slip
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