Performer RPM
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Sep 18, 2022, 08:08 PM
Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
You can get it under the hood by using a drop base air cleaner, but the drop base will cause the top of the air cleaner to be so close to the carb's airhorn that you will actually end up with a loss in performance due to airflow restriction to the carb compared to just using the stock intake manifold. The minimum distance from the carb's aircleaner gasket on the airhorn to the bottom of the aircleaner lid, to avoid serious upper-rpm performance problems, is 3 inches. Most aircleaners have a 1" "dome", which means that the minimum distance from the aircleaner gasket on the carb to the top surface of the air filter is 2 inches. So, for example, you cannot run a 2" tall aircleaner on a drop base to make it fit under the hood - it puts you way below the 2" minimum height required above the carb. I've tested it, and it sucks... I see people doing it all the time, and I get e-mails asking the question, "why does my car fall on its face at high rpm with my new RPM intake manifold?"
Lars
Lars
Tech Contributor
Joined: Aug 1999
Posts: 14,379
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
You can get it under the hood by using a drop base air cleaner, but the drop base will cause the top of the air cleaner to be so close to the carb's airhorn that you will actually end up with a loss in performance due to airflow restriction to the carb compared to just using the stock intake manifold. The minimum distance from the carb's aircleaner gasket on the airhorn to the bottom of the aircleaner lid, to avoid serious upper-rpm performance problems, is 3 inches. Most aircleaners have a 1" "dome", which means that the minimum distance from the aircleaner gasket on the carb to the top surface of the air filter is 2 inches. So, for example, you cannot run a 2" tall aircleaner on a drop base to make it fit under the hood - it puts you way below the 2" minimum height required above the carb. I've tested it, and it sucks... I see people doing it all the time, and I get e-mails asking the question, "why does my car fall on its face at high rpm with my new RPM intake manifold?"
Lars
Lars
Thread Starter
Heel & Toe
Joined: Sep 2022
Posts: 20
Likes: 2
From: Rhode Island
Thanks for the responses. I have a 2101 edelbrock now but will be rebuilding the engine this winter/spring and was curious if it would fit.
Nothing wrong with the 2101, just curious.
Is the Performed EPS any better than the standard performer? They look almost the same.
Nothing wrong with the 2101, just curious.
Is the Performed EPS any better than the standard performer? They look almost the same.
Tech Contributor
Joined: Aug 1999
Posts: 14,379
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From: At my Bar drinking and wrenching in Lafayette Colorado
If I were you, I'd use the stock 1978 L82 aluminum manifold. Your'e not going to gain any advantage by using any other aftermnarket manifold that fits under the hood. Whether you use the Performer or the Performer EPS wont' make any difference, and it will run about as well as the stock intake. Edelbrock modelled the Performer intake after the L82 intake. Ever wonder why they look almost identical..?
Lars
Lars
Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
Your limitation is that horrible little outdated Carter AFB carb (aka, "Edelbrock Performer" 1406) - not your intake. Put a well-built 750 cfm Q-Jet on your L48 intake, combined with a good timing curve, and the car will snap your head off. You can modify that intake to really make it run by cutting down the secondary wall divider about 3/8". That, combined with the cfm of the stock Q-Jet, will really wake it up. Stop catering to the marketing gimmics at Edelbrock and your car will run really well...
Lars
Lars
Le Mans Master
Joined: Jun 2019
Posts: 7,653
Likes: 2,468
From: Indiana
Your limitation is that horrible little outdated Carter AFB carb (aka, "Edelbrock Performer" 1406) - not your intake. Put a well-built 750 cfm Q-Jet on your L48 intake, combined with a good timing curve, and the car will snap your head off. You can modify that intake to really make it run by cutting down the secondary wall divider about 3/8". That, combined with the cfm of the stock Q-Jet, will really wake it up. Stop catering to the marketing gimmics at Edelbrock and your car will run really well...
Lars
Lars
I can testify to that fact..
Lars, is the l82 aluminum manifold any different at all from the cast ones other than weight ?
thanks
Fyi my carb you rebuilt over 5000 miles on it..runs perfect!
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Melting Slicks
Joined: Jul 2006
Posts: 2,291
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From: Salmon Arm, BC
I'd start down the weight loss road and put an aluminum manifold on there instead of the cast iron piece.....you'll do it eventually, so why not start now.
I have a Performer RPM with a 3" filter on a drop base and it fits on my stock 77 hood with about 1/2" to spare.
I have a Performer RPM with a 3" filter on a drop base and it fits on my stock 77 hood with about 1/2" to spare.
Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
That's what I'm trying to advise you on.
As noted, the 2101 is a copy of the L82 GM intake. It works just great, and there is no reason or gain in changing over to a Performer RPM or Airgap manifold - it will gain you nothing other than problems. The 2101 is a dual pattern manifold, so if you want to improve the performance of your car, skip the manifold swap, ditch the obsolete AFB carb (aka 1406), and get a rebuildable '78 Q-Jet mounted to the 2101 to make your car run right.
As noted, the 2101 is a copy of the L82 GM intake. It works just great, and there is no reason or gain in changing over to a Performer RPM or Airgap manifold - it will gain you nothing other than problems. The 2101 is a dual pattern manifold, so if you want to improve the performance of your car, skip the manifold swap, ditch the obsolete AFB carb (aka 1406), and get a rebuildable '78 Q-Jet mounted to the 2101 to make your car run right.
Team Owner
Joined: Jan 2006
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From: Into the Mystic And yet, despite the look on my face, you're still talking TN
St. Jude Donor '09 thru '25
Your limitation is that horrible little outdated Carter AFB carb (aka, "Edelbrock Performer" 1406) - not your intake. Put a well-built 750 cfm Q-Jet on your L48 intake, combined with a good timing curve, and the car will snap your head off. You can modify that intake to really make it run by cutting down the secondary wall divider about 3/8". That, combined with the cfm of the stock Q-Jet, will really wake it up. Stop catering to the marketing gimmics at Edelbrock and your car will run really well...
Lars
Lars
gotta pay for all that advertising
Race Director
Joined: Jun 2000
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From: FL
Tech Contributor
Joined: Aug 1999
Posts: 14,379
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
No, it's not. Ditching the 1950's carb and getting a 1970's 750 cfm Q-Jet is. If you find a '78 L82 carb, it's 800 cfm. Your manifold is not your limiting issue.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
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From: Cool Northern Michigan
Barry,
I assume my '77 hood is the same as your '78. I am in the process of installing Edelbrocks 7501 Air Gap this month with a Holley 4150 model.
According to my high tech measure device, AKA Silly Putty placed on a 14" chrome air cleaner, I have 3/8" of hood clearance with the drop base.
I also have solid motor mounts so the air cleaner will never tag the hood.
I was more concerned about Holley fuel bowl vents to air cleaner lid clearance than hood clearance. Holley wants 3/4" for that. So, I had custom fuel bowl vents made.
I also found a 14" dia filter but only 2 &.7/8" tall at Advance Auto.
For what it's worth, there are 2.5" and 2.750" filters out there. Really have to do some research to find any under 3" but more than two inches.
The Air Gap design keeps the hot oils away from the carb base. This concept in itself is a win-win in the small, over heated confines of a C3 engine bay.
The Air Gap is supposedly worth another 22+ horse.
I assume my '77 hood is the same as your '78. I am in the process of installing Edelbrocks 7501 Air Gap this month with a Holley 4150 model.
According to my high tech measure device, AKA Silly Putty placed on a 14" chrome air cleaner, I have 3/8" of hood clearance with the drop base.
I also have solid motor mounts so the air cleaner will never tag the hood.
I was more concerned about Holley fuel bowl vents to air cleaner lid clearance than hood clearance. Holley wants 3/4" for that. So, I had custom fuel bowl vents made.
I also found a 14" dia filter but only 2 &.7/8" tall at Advance Auto.
For what it's worth, there are 2.5" and 2.750" filters out there. Really have to do some research to find any under 3" but more than two inches.
The Air Gap design keeps the hot oils away from the carb base. This concept in itself is a win-win in the small, over heated confines of a C3 engine bay.
The Air Gap is supposedly worth another 22+ horse.
Last edited by HeadsU.P.; Sep 20, 2022 at 05:59 PM.
Tech Contributor
Joined: Aug 1999
Posts: 14,379
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From: At my Bar drinking and wrenching in Lafayette Colorado
Robert -
You really need to watch that 3" and 2" air cleaner and lid spec I outlined above. I've tested it both on the dyno and at the track, and that number is real. If you get that clearance below 3", horsepower starts dropping dramatically. Distance to the bowl vents is not the issue, but if you're that close to the vents, you're way too close to the airhorn with the air cleaner lid, and you are seriously and adversely impacting airflow into and through the carb. Give it a shot next time you have an engine on the dyno (or try it at the track) - you'll be shocked at the results.
Lars
You really need to watch that 3" and 2" air cleaner and lid spec I outlined above. I've tested it both on the dyno and at the track, and that number is real. If you get that clearance below 3", horsepower starts dropping dramatically. Distance to the bowl vents is not the issue, but if you're that close to the vents, you're way too close to the airhorn with the air cleaner lid, and you are seriously and adversely impacting airflow into and through the carb. Give it a shot next time you have an engine on the dyno (or try it at the track) - you'll be shocked at the results.
Lars
Burning Brakes
Joined: Sep 2019
Posts: 923
Likes: 155
From: North Port, FL
I can attest to the truth on this. I'm going thru the same problem now and because I have Vortech heads. I'm limited in manifold choices. I've discussed this at length with Lars and have tried every combo I can to get it to breath. My only solution now is a taller hood. LT-1 or taller to even come close, or a scoop. For your reference my car is a 72 L48 with a GM 383 with Vortech heads. No workie with any carb/air cleaner combo. I've started a thread on this. With your later hood it may fit, but it might not breath too good.
Robert -
You really need to watch that 3" and 2" air cleaner and lid spec I outlined above. I've tested it both on the dyno and at the track, and that number is real. If you get that clearance below 3", horsepower starts dropping dramatically. Distance to the bowl vents is not the issue, but if you're that close to the vents, you're way too close to the airhorn with the air cleaner lid, and you are seriously and adversely impacting airflow into and through the carb. Give it a shot next time you have an engine on the dyno (or try it at the track) - you'll be shocked at the results.
Lars
You really need to watch that 3" and 2" air cleaner and lid spec I outlined above. I've tested it both on the dyno and at the track, and that number is real. If you get that clearance below 3", horsepower starts dropping dramatically. Distance to the bowl vents is not the issue, but if you're that close to the vents, you're way too close to the airhorn with the air cleaner lid, and you are seriously and adversely impacting airflow into and through the carb. Give it a shot next time you have an engine on the dyno (or try it at the track) - you'll be shocked at the results.
Lars
Le Mans Master
Joined: May 2007
Posts: 5,025
Likes: 1,120
From: North tonawanda NY
If I were you, I'd use the stock 1978 L82 aluminum manifold. Your'e not going to gain any advantage by using any other aftermnarket manifold that fits under the hood. Whether you use the Performer or the Performer EPS wont' make any difference, and it will run about as well as the stock intake. Edelbrock modelled the Performer intake after the L82 intake. Ever wonder why they look almost identical..?
Lars
Lars
On a serious note engine masters did a good episode on air cleaner assemblies and it showed pretty well how badly the drop base air cleaner hurt performance.
Ive also seen many many dyno comparisons between the rpm and the air gap and once again (engine masters) proved the gains in the air gap are all from the center divider notch in the air gap manifold by quickly cutting the same notch in the rpm and matching the results of the air gap. (if you can fit it an open spacer does this also.) Then again most of the tests ive seen only show about 7-12hp difference from the eps and the air gap, and thats on an engine with better heads and exhaust that can actually draw in more air flow and make use of it.
Last edited by augiedoggy; Sep 20, 2022 at 01:00 PM.