Hey all, I got a question...

I've got a 77 Vette with the L48. I'm swapping out the stock intake with a Weiand 8004. The qjet has seen much better days, so a new carb is in order. This car is a driver, so which carb should I go with? The 4175 is the easiest replacement, but would I get better performance out of the Street Avenger? Or would one of the BG Road Demons be a good fit? I'll be adding a Comp Cams XE256 cam soon, so factor that in, too. I'm wanting low to mid-range torque, HP will fall where it falls, no races in this Vette's future. Any and all opinions welcomed!

The Weiand Action Plus manifold is designed for a spread bore type carb. I don't have any experience with a Holley spread bore carb. I might would stay with the Q-Jet if this manifold is used. If you want to use a Holley or Barry Grant square bore carb, I would use a different manifold designed with a square flange, Weiand Stealth or Edelbrock Performer. I like the Holley 750 cfm vacuum secondary for the street or the 4150 series (double pumper) for more performance. I don't have any personal history with Barry Grant, but they took Holley's standard design and made it better. The trick to performance with these carbs is "Tuning" for your application.

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sstanford '76 L48

You might consider having your Q-Jet properly rebuilt. It's an excellent carburetor and by re-using it, you won't have to worry about modifying your fuel line, filter, linkages, and the kick-up solenoid if you have a/c. Not that this can't be done pretty easily, but doing so does kick up the costs pretty quickly.

Regardless of what you do, you may still have to have the carburetor "tuned" to the new cam. My '78 has a bigger cam installed by a prior owner, and it wouldn't idle at all. I had my Q-Jet rebuilt, which made a big difference, but the idle was not what it should have been. It turns out with the non-stock cam it was creating a too lean condition at idle. Having my Q-Jet re-jetted with a larger set of jets made all the difference. When you decide on a carburetor, consider contacting Comp Cams and ask them if their camshaft will require modifications to the carb. When you change a component to one of different specs, it requires other changes to get maximum benefits.

I have no personal experience with Demon Carbs, but they do have an excellent reputation. The guys at a local speed shop call them "Holley's that work".

i'll agree with you guys, barry grant took a holley and made it work. Last summer I replaced my carb with a 759 barry grant. I must say, when jetted properly, it performs flawlessly. None of the problems that i have had on other various holleys. If you want performance while playing a little with settings, then i might look into a bg.

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sorry, that was a 750 bg, who in the wolrd would make a 759??

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I've had the Holley 4175 for a couple of years and haven't had any problems. I did change the discharge nozzle to a 21 and played with the plastic cams. Out of the box they are setup pretty rich. I would look at getting your Q-jet fixed if you can. They are very good carbs when setup correctly.

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Brian - NCM Lifetime Member

73 coupe L48, Flat-top pistons, Performer RPM Heads, Crane Cam and roller rockers, Holley 650 vac sec. Performer intake,
3.55 gear BTO 200-4R trans,
Leather seats, Seatbelt Plus 3point seatbelts, Pioneer CD player
Magnaflow Exhuast System

I was gonna try to work with the Q-jet if I could, but it is probably beyond repair. Everything is pretty loose and the threads have stripped out of the air cleaner stud hole. I'm gonna replace it. I've got it narrowed down to the 4175, the Street Avenger and a BG Road Demon. Decisions decisions!

Thanks for all the replies! Keep 'em coming, this is a big deal for me.

Actually the 8004 has both bolt patterns and will work with square and spread bore carbs. If your Vette is a Automatic you will want a vacuum secondary. Stick a double pump. You would be real happy with a 670 Street Avenger with the weiand Intake. They work well together. I have nothing against a demon, but have heard more negative then positive. Mostly from people I have spoke with on the Hot Rod Power Tour and Super Chevy events. I've owned Q-jets and they work fine, sometimes, but not all the time. If you change to a Holley or Demon, you will need to change your linkage mounting brackets to work with these carbs. Something to think about.

Based on the cam you have selected and depending on what your goal is this cam is smaller then most most people go too when swapping in a cam. I guess what I'm saying is you may want to check into what is the maximum cam you can get away with considering everything, ie. final gear, headers, exhaust, trans, intake, carb, CID, weight, Carb. etc. Only reason I bring this up is because its a pain to swap the cam out once the engine is back in or while its still in the car.

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Just a note:
I bought the Holley 4175 because it was suppose to be a direct replacement for the Q-jet. It works real well with my setup.
Two things that are different then the Q-jet:
1. My aircleaner did not sit flat without a spacer because it hit on the vac sec modual(Aircleaner for the cowl induction hood has a 12"dia. filter).
2. The brake booster vac hook up at the back, base of the carb is smaller thread so I had to use an adapter.

Throttle linkage and the fuel line hooked right up.

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Brian - NCM Lifetime Member

73 coupe L48, Flat-top pistons, Performer RPM Heads, Crane Cam and roller rockers, Holley 650 vac sec. Performer intake,
3.55 gear BTO 200-4R trans,
Leather seats, Seatbelt Plus 3point seatbelts, Pioneer CD player
Magnaflow Exhuast System

I picked the cam I did because it is a dual pattern that gives strong low end torque but still has an aggressive exhaust profile . I haven't bought it yet, and I'll most likely talk with the guys at Comp Cams before I do. Thanks for the heads up. As far as the carb, I ended up going with none of the above (figure that!). All the motor heads I talked to around here said the Edelbrock 600 had the most bang for the buck. If I'm not happy with it, I'll most likely go with the Holley Street Avenger 570 or 670. Since this car is a driver (45 miles one way to work) mileage is a consideration. After I get the engine compartment squared away, then we gonna do a tranny swap to a 200R4 or (more likely) a 700R4 from BTO, then bring the rear up to a 3:36 or 3:55. But that's a few house plans away...

I appreciate all the input. I would have saved the Q-jet (I'm not trashing it by the way) but it had gotten to the point of throwing good money after bad, and I don't have a lot to throw.

Carb problem (hopefully) solved. Cam's next.

if you're looking for mileage, the edelbrock is your best bet. Just curious, what kind of mileage does an L48 auto get?? I wouldn't be surprised if it's double that of mine. Good luck with the decisions.

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If I keep my foot out of it I get about 15 mpg average. Which really isn't bad considering the age of the car. The problem is that I love the power (the torque is decent, even if the HP isn't) so I'm having a hard time keeping my foot out of the carb!


Y'all know what I mean, don'tcha?

Had the Edelbrock 600 cfm (#1406) -- worked great. Put in the same cam as you're thinking about, XE 256. Talked to Comp and they said it would be great on the street, especially with a Performer manifold and carb. Upped the carb to the Edelbrock #1813 (Thunder series AVS 800 cfm). Dyno torque is at 408 lb-ft. With a peral orange '73 the cops can see me coming from a mile away, figured they didn't need to hear me as well.

Cool, at least I know I'm on the right track!

Just to update, I got the carb and manifold and new Mickey Thompson valve covers installed today. That q-jet was worse off than I thought! She's never run this smoothly. 5 minutes to dial in the idle. Simple. No flat spots, great acceleration. So far I'm pleased with the results. Thanks for all the help!