Duke94

I bought a Edelbrock 1400 (600 CFM) carb a year ago and finially got around to doing something with it. When comparing it to the stock Quadrajet on my 78, the secondaries on the Quadrajet look a whole lot bigger than the Edelbrock. Anyone know the CFM of the 78 Quadrajet, and is it even worth installing the Edelbrock?

JCL

Gary. Don't know the CFM of the Quadrajet, but the 750 Edelbrock/Stealth manifold combo on my "383" WORKS super. JCL :yesnod: :yesnod: " Have Baffles.Will Travel"

Oldguard 7

The Edelbrock carb was a design used extentively in the 50's. The Edelbrock carb is a rebuilt Carter AFB (Aluminum Four Barrel) carb.
The Quadrajet carb came out in the 60's. When you punch it the secondaries (which are much larger than the Edelbrock) open to allow more fuel and air into the engine. It works as well as a 750cfm carb. I too have a 600cfm Edelbrock carb on my vette and regrettibly I gave the quadrajet to one of my instructors while attenting Lincoln Technical Institute (Mechanics School). Should have known I was making a mistake when his face lit up. Both are good carbs but I wish I had the quadrajet sitting atop my manifold. Hopes this helps some.

Cali,68,L-79

Agree with JCL, my motor literally changed to a new beast with the Eldebrock. The Eldebrock 1400 is a mechanical secondary 600cfm while your QJ is a 850 cfm vacuum secondary so port side is not important due to source vacuum is completely different than mechanical secondary action. I literally took it out of the box and adjusted the fuel ratios and the rest is history.

Tom73

The Q-jets used on Vettes were all 750 CFM. There were some q-jets used on Olds/Buicks that were in the 800-850 range.

tom...

Duke94

Thanks for the responses. I think I'll give it a shot.

page62

One question: Why do you want to install the Edelbrock? It's a great carb for the strip/competition, but the QJet is the better all-around street & daily driver carb.

joe73vette

Yes, most Q-jets are 750 CFM. The Olds/Buick/Caddy ones are over 800. You can easily tell by looking down the primary throats - there is hardly any neck-down in the bigger ones. Also, the gas comes in from the front center on non-Chevy carbs. Joe

Duke94

I hoped for more power. I also have their aluminum heads and manifold and a XE268 cam. It's suppose to be a street machine.

page62

What engine do you have? What is your current exhaust setup? Do you have emissions testing in your area?

BeaterShark

The Edelbrock Performer carb is a square bore, where the Q-Jet is a spread bore carb.

The square bore carb has equal sized primary and secondary bores. The spread bore has small primary bores and large secondary bores. This gives it the capability of geting beter economy without giving up much if any performance.

The Q-Jets were made in either 750 or 795 cfm depending on application.

BeaterShark

This is completely wrong. Both are mechanical secondary with the vacuum operated air valve. Also, the only 850cfm Q-Jet is the new Edelbrock ones labeled "Performer RPM Q-Jet Carburetor".

timbo79

The Edelbrock #1903 is a direct replacement for the original Q Jet... I think they run in model #'s 1901- 1904, depending on year and choke (hot air or elec). They work great, are adjustable and are 795 cfm, unlike the 1400 model series.

Good Luck

joeveto

CFM really doesn't dictate ultimate horsepower. You need a pretty nasty engine, to outgrow 600CFM. You really need to look at what your needs are from a driving point of view. I think both carbs can fit the bill, whether you're racing or cruising. Although I think the Quad is definitely a better, all around carb. The Edelbrock, on the other hand, is a simpler design, and it's much easier to tune and understand. I may still go back to the Quad, as I do a lot of low intensity cruising. But for now, the Edelbrock is my choice.

page62

I have an Edelbrock 1903. The installation was plug-n-play. And I imagine I could get even better performance if I actually tuned it...

Duke94

The engine started out as a GM Goodwrench create motor that I added Edelbrock heads, manifold, cam and carb too. I kinda followed the build up that Chevy HP mag did a while back with the GM Goodwrench motor. Exhaust is hooker headers and side pipes. No emissions testing in my area. Any suggestions on carb tuning?