levic482

I have a 1977 corvette 350 auto with ram manifolds and cat delete. I plan on putting a holley 670 street avenger on it with a edlebrock intake but I don't know if I should get performance rpm, air gap, vic jr ? I only drive it on the street. I do plan on modifying it more but not for a couple years after this.

Vetteman Jack

Moved to C3 Tech.

derekderek

the diff in performance between the 750 q-jet and any other carb including another q-jet is the diff in condition of the individual carbs. it won't run better because it is a holley. or be any more powerful. the intake will also make very little difference. not really enough to justify the expense and time.

Rescue Rogers

Don't forget to check hood clearance. When buying performance bolt on parts, try and consider the end RPM range you want the power to come in at and what RPM you want torque at, that will give you an end goal for all the future parts you want. For the street the dual plane RPM is the best. For the strip the torquer is a better choice

I have a Edelbrock RPM with a quadrajet, but I run a bigger cam and current aluminum heads. If you're looking for a little performance, heads cam and intake should all work together and are the best combo to change for a performance gain. A drop base air cleaner helps alot with the hood clearance issues or a hood scoop

jb78L-82

Correct and Agree!

jb78L-82

Do a search on intake performance on moderate HP SBC builds in magazines and in most cases, you find the intakes that fit under the hood of a C3 will make little to no difference in HP/TQ versus a factory aluminum L-82 intake. When I had the bottom end of my OEM L-82 rebuilt by a known expert builder in my area who has built 100's of GM engines and dynos them as well including 1,000 HP modern LS engines told me that sub 6,000 RPM the L-82 aluminum intake was pretty good for power. He mildly ported my OEM L-82 intake for me (I did the rest of the build myself on the L-82) and the L-82 intake is really good on my rebuilt L-82 355 with roller cam, AFR heads and 10.2 compression. The edelbrock performer is no better than the factory L-82 intake, the performer RPM will give you maybe 5-7 HP over the factory intake on a stock to mild build at higher RPM, MAYBE, and most of the others will not fit under the hood. One of the best replacement intakes is the GM chevrolet performance intake...good for 10-12 hp on a 500 Gross build, at best......5-7 HP average increases on a moderate build will NOT be noticeable..its too small an increase.....for the trouble

HeadsU.P.

If you want to up grade your intake & carb, then by all means do it! Its your car, your money, your time. Even if its only for a few horses, you can do it for the bling.
A nice Eddy with a nice Holley looks fantastic when you pop the hood. Much better than the stock crapola, boring, 160-180ish horse that's on there now.

With the Air Gap, you will need a drop-base air cleaner. Another chance to add more bling. And for what its worth, a dyno mule test engine showed 18 more horse with the Air-Gap over the 2101.

Do it for the car. Do it for the next owner. Do it for yourself.

jb78L-82

Nope!

Read Here:

https://www.hotrod.com/articles/dual...d-comparisons/

The edelbrock air Gap over the Performer (same as the L-82 intake BTW) is 10 peak TQ and 2 peak HP...^^^^^^^^^^^^on a 500 Gross HP SBC!!!!!

The Air gap over the Chevrolet ZZ4 intake (which in my opinion is the BEST intake to fit under the C3 hood) advantage is 4 peak TQ and 13 peak HP deficit.....that would be LESS HP.

As stated previously, if you are chasing every last HP/TQ AND you have a significant HP build, by all means, use a non stock intake. There is very little advantage on a stock engine or mild build over the stock intake. There are much better places to spend dollars for increased power.....The bargain power intake for a stock motor or mild build is an aluminum L-82 intake that you can hand port yourself...............even a mild porting shows significant gains on The L-82 intake.....If I ever change out my ported L-82 factory aluminum intake, I would hands down use the GM Performance ZZ4 intake on a C3...by far....

Crimson Thunder

I would do it just for the weight savings. I recently gave away an iron intake off a 79 Corvette and forgot how heavy those things were.

jackson

OP
? Cat delete right? But you still have merged exhaust pipes ... effectively single exhaust right? ... I don't mean dual tips.
Can you install true dual exhaust where you live? (separate exhaust pipe & muffler for each bank of cylinders)...
... If you can, you'll get lots more gain from that than a new intake manifold and carb.
FWIW, the OE QJet cab flows 750 (versus holley670) and properly set QJet works better than any other carb.

jb78L-82

Holy crap!

Of course folks should do anything that they want to their cars!!!!

My comments in no way are trying to dissuade someone, anyone, all, from spending their money on their C3's....NOT THE INTENTION, EVER, just to be very clear!

What I am saying, in this case, about intakes (the "argumentative crap", as you said) and, in all cases, when I am being

"difficult" is that, IN MY OPINION, AND based on a substantive documentation (Hotrod Magazine,in this instance), my personal experience with my C3, expert testimony from an extremely knowledgeable source like my owner/friend at Maximum Performance, etc, that changing intakes alone on a mild build/stock engine, most likely, will not yield 18 HP with a low rise intake...sorry....

Again, a low rise intake change on a stock to moderate engine will net about 5-7 HP, maybe, and 10-12 HP with a medium/high rise intake, optimistically, on a 500 Gross SBC, at best.

The constant drone that providing reasonable factual information as being misleading is rather boring, frankly, and disingenuous to posters asking for legitimate opinions...............BTW-provide any opinion you want BUT best to leave it alone if others who provide a counterpoint with facts and personal experience.....that is a major NO NO......that is where all of these discussions go very wrong......

HeadsU.P.

That's the thing about forums: 60% gospel truth & 40% non fact opinions. And its up to the reader to decide which is which.
But anyway, one dyno can show no gain to 5 horse gain. Another dyno can show four or five times that amount.

Exact horsepower numbers are not what's important here. What is important is up grading from stock for the learning experience, resale value and adding some bragging rights or bling as some call it.

Up grading the fuel system is always worth it, in my opinion. Some owners will sink a $1,200 into wheels / tires. Some spend $800 on interiors. Some spend two grand on heads.

Spending $700 on carb & intake seems like well invested money to me. To each their own.

Jebbysan

The 2701 EPS or the 2101 Performer flow way better and is a solid upgrade over the stock intake although if your Q-jet works well just put it on a 2101.
Block the heat riser with a 1204 Fel Pro....then add long tube headers of your choice.......
These two changes will net huge gains in the low to mid range......when combined with a proper ignition curve. There is not doubt or conjecture to this.....the gain is huge over the pathetic Q-jet intake and rams horn manifolds....and has been documented ad nauseum over the years......
Plus it cleans up the engine compartment and the headers delete the silly heat riser.

Jebby

jb78L-82

Long Tube Headers, as a single modification, on any motor, will provide hugh gains over the stock ram horns, X2 for a moderate built engine, and X3 for a higher HP motor......

REELAV8R

I can tell you from my own experience with a 77 and a q-jet carb, that you have a great carb already. It may
need tuning and maybe an overhaul by Lars. You’ll be money ahead and have a more responsive and fuel efficient carb in the end.

I’m using a 2101 performer intake on my 440 hp 350 in my 77 and it performs well. Granted I did port it out to accommodate the higher hp, but before that it still worked well with no under hood clearance issues, even with stock air cleaner arrangement.

OldCarBum

If you plan to add additional performance equipment in the near future, make a plan for the entire project, then start purchasing your parts.
Once you have everything sitting on the shelf, tear it apart and do the work just once.
Exhaust, intake and carb are great improvements, but if you are considering heads, cam or an entire rebuild, do your research so everything is working together and you will be happier with the end result.

BLUE1972

jb78L-82

This ^^^^^is the documentation I referenced earlier in #8!!!!!

Pretty much no low rise manifold on C3 with a stock hood is going to do much over an aluminum L-82 or LT-1 intake (X2, if you even mildly port, the stock aluminum intake for sub 6,000 RPM operation)......as stated previously, AND on a 500 TQ/HP Gross engine in this example, no less....the gains on a mild build or stock engine will be negligible to none. The Chevrolet ZZ4 intake, IMO, is the best of the low rise intakes over the edelbrocks, all of them,.....including the Performer RPM......

Either way, on the test mule above, 5-8 TQ/HP on a 500 TQ/HP engine will not be felt, not a chance.............bragging rights only......

Street Rat

I'm running the Performer EPS and the Holley 670cfm Ultra Avenger. It fits under the hood of my '81 with about 1/4" of clearance. The carb has four corner idle and is infinitely adjustable as are most of the Holley carbs. This combination works great for me.

Jebbysan

Now go bolt a Q-jet intake on that 460 hp engine.....
That these low rise intake do so well on an engine that moves this much air speaks volumes.....
I know for a fact that a better intake is worth about 20 all over.....
You have been defending the Q-jet intake for a long time and that is fine.....but the EPS is so much better designed....you can literally look at it and see that it is a much more thought out design.....
The manifold will make power.....and clean things up....plus delete EGR and heat riser.....putting an intake on these engines is a solid upgrade....doing it with long tube headers and a curve is how they should have came from the factory.....it is a night and day difference.....but from there you have the **** heads....and that is the ultimate cork....
I find it funny that GM spent the money developing the DZ/LT-1 intake to bolt on those crap heads....no way to make even the advertised rating....that manifold will support about 475 horsepower.....but putting it on an L-82 will pickup about 20 like an aftermarket.....
The Q-jet 4 hole manifold is a woefully bad flowing and bad distributing intake.....if you have one on a car and it runs awesome....great, but I am here to tell you that anything is better.
And just so we are clear.....there were no aluminum intakes bolted on L-82 small blocks....they all got that low rise turd.....the LT-1 is a high rise unit....and was put out to pasture in 1972.....

Jebby