Stock 1978 454, Air Gap Intake, Quadrajet? - Chevelle Tech
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post #1 of 20 (permalink) Old Feb 14th, 19, 8:53 AM Thread Starter
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Stock 1978 454, Air Gap Intake, Quadrajet?

Would it be worth it to swap to the Air Gap intake manifold on a stock 1978 454 motor.. I like the look of them and was wondering If it would add any performance over the stock Quadrajet intake. I would be using the Quadrajet carb, it runs perfectly.

I'm trying to make my 454 look like a 427 in my 69 el Camino SS396. Maybe Tri Power would be a better way?

Thank you..
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post #2 of 20 (permalink) Old Feb 14th, 19, 9:18 AM
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Re: Stock 1978 454, Air Gap Intake, Quadrajet?

Swapping to the Air Gap will certainly help out in adding a little bit of HP and torque,even with it being stock.
IMHO,if you want the "427 look" add a reproduction GM "163" casting high rise square port intake and you can use a square bore to spreadbore adapter with your qjet.
Of course, a vintage Holley 3310 would really hit it out of the park..but qjets do work well.
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post #3 of 20 (permalink) Old Feb 14th, 19, 9:36 AM
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Re: Stock 1978 454, Air Gap Intake, Quadrajet?

Edelbrock or no other I know of make air gap intake that has spread bore bolt pattern for the BBC of course you can use an adapter.
Edelbrock rpm 7164 is the regular rpm q-jet version.
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post #4 of 20 (permalink) Old Feb 14th, 19, 9:53 AM
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Re: Stock 1978 454, Air Gap Intake, Quadrajet?

If the 1978 454 is truly stock, it has "peanut port" heads - and a very tiny cam! This was done to make lots of low end torque at the cost of higher RPM power. If you want an aftermarket manifold for that the Edelbrock Performer 2-O would be a better choice as it is a "peanut port" intake. The Air Gap is made for Large Oval Ports.
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post #5 of 20 (permalink) Old Feb 14th, 19, 9:57 AM
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Re: Stock 1978 454, Air Gap Intake, Quadrajet?

It will help, but I would swap the carb with an Edelbrock as well.
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post #6 of 20 (permalink) Old Feb 14th, 19, 9:58 AM
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Re: Stock 1978 454, Air Gap Intake, Quadrajet?

I would look at the weiand 8122 if it has peanut port heads, and you want a spreadbore manifold.

https://www.summitracing.com/parts/wnd-8122/overview/
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post #7 of 20 (permalink) Old Feb 14th, 19, 10:02 AM
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Re: Stock 1978 454, Air Gap Intake, Quadrajet?

Last bone stock,untouched 1978 454 I worked on was a 361959 casting with 781 heads.
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post #8 of 20 (permalink) Old Feb 14th, 19, 10:17 AM
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Re: Stock 1978 454, Air Gap Intake, Quadrajet?

Quote:
Originally Posted by mr 4 speed View Post
Last bone stock,untouched 1978 454 I worked on was a 361959 casting with 781 heads.
I was under the impression that they went to peanut port heads in 77.

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post #9 of 20 (permalink) Old Feb 14th, 19, 10:20 AM
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Re: Stock 1978 454, Air Gap Intake, Quadrajet?

I agree with Mr. 4 speed, I also had an untouched 78 vintage 454 with 781 heads.
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post #10 of 20 (permalink) Old Feb 14th, 19, 10:24 AM
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Re: Stock 1978 454, Air Gap Intake, Quadrajet?

Quote:
Originally Posted by 71454Chevelle View Post
I was under the impression that they went to peanut port heads in 77.
I have seen them with 236 peanuts and 781 ovals.
last one I touched had 781 heads

either way, the RPM or RPM Air gap will wake up a stock 454

and IMHO and experience,the carb you chose is a personal choice.
I personally love the 3310 on my big block...runs in the 11's and I can drive it anywhere. Lights the tires up at highway speeds. And I haven't touched the carb in many years (I bought it 18 years ago)
That's reliability and performance in my mind.

..and a Qjet works well on a 454. A fellow member here got his numbers matching all 100% stock (except for Hooker headers) 1974 454 4 speed Corvette into the mid/low 13's


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post #11 of 20 (permalink) Old Feb 14th, 19, 10:41 AM
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Re: Stock 1978 454, Air Gap Intake, Quadrajet?

Quote:
Originally Posted by mr 4 speed View Post
I have seen them with 236 peanuts and 781 ovals.
last one I touched had 781 heads

either way, the RPM or RPM Air gap will wake up a stock 454

and IMHO and experience,the carb you chose is a personal choice.
I personally love the 3310 on my big block...runs in the 11's and I can drive it anywhere. Lights the tires up at highway speeds. And I haven't touched the carb in many years (I bought it 18 years ago)
That's reliability and performance in my mind.

..and a Qjet works well on a 454. A fellow member here got his numbers matching all 100% stock (except for Hooker headers) 1974 454 4 speed Corvette into the mid/low 13's
X2 on the 3310 but a well build qjet will also work very good.

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post #12 of 20 (permalink) Old Feb 14th, 19, 9:08 PM Thread Starter
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Re: Stock 1978 454, Air Gap Intake, Quadrajet?

The passenger side head under the valve cover has these numbers.

336781

GM12T

E8078

Can you tell what heads these are?
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post #13 of 20 (permalink) Old Feb 14th, 19, 9:18 PM
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Re: Stock 1978 454, Air Gap Intake, Quadrajet?

they are 781s. last 3 digits of the casting number. good heads
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post #14 of 20 (permalink) Old Feb 14th, 19, 10:55 PM
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Re: Stock 1978 454, Air Gap Intake, Quadrajet?

It would be easier and more authentic-looking to dress the 454 up look like a 350 horse 396 -- you could keep your Q-Jet.
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post #15 of 20 (permalink) Old Feb 15th, 19, 5:19 AM
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Re: Stock 1978 454, Air Gap Intake, Quadrajet?

FWIW a regular Performer RPM looks a lot more like the GM 163 intake than the Air Gap IMO.
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