# Carb Swap?



## Petey D (Feb 14, 2009)

Hi guys,

I'm thinking of swaping the stock Q-Jet on my Lemans for a 600 Holley.

Does anybody have any experience with the swap & what if any will be the difference in performance?

Thanks.


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## Rukee (Feb 8, 2007)

I have a personal distaste for holley carbs. I would do an electric choke Durashine Edlerbrock unit. It'll perform well out of the box and looks tons better with no maintenance to keep the shine up.


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## Mcantw (Sep 7, 2008)

I've recently got rid of my carter q-jet for a 750 Edelbrock and I have had no issues. My car is a clone so I'm not interested in numbers matching. I did have to get an adapter plate for the change over.


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## Petey D (Feb 14, 2009)

Edelbrock eh? The thought has crossed my mind, I'm not gonna lie. They're affordable and readily available.

750cfm wouldn't be too much for my motor? I've got a 383 Small block.

Sorry, I'm carb ignorant, used to dealing with efi.


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## Rukee (Feb 8, 2007)

750cfm would be great.


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## jeffbgto (Feb 15, 2009)

I would use a Eldebrock as well if you do not want the stock Q-Jet. I personally have had great luck with the old Q-Jets, it just usually takes 3 to build one good one. Once its good it tends to stay that way. I have not had good luck with holleys on Pontiacs.
my $.02


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## GTO'n'TRANSAM (Nov 13, 2008)

Well my Holley Street Avenger 670cfm should be put on tomorrow...I now have a sense of foreboding! :willy: Its being put on a '67 LeMans with a '67 400 with an original 2bbl.


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## 68greengoat (Sep 15, 2005)

jeffbgto said:


> I would use a Eldebrock as well if you do not want the stock Q-Jet. I personally have had great luck with the old Q-Jets, it just usually takes 3 to build one good one. Once its good it tends to stay that way. I have not had good luck with holleys on Pontiacs.
> my $.02



:agree as far as the Q-jet.


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## Petey D (Feb 14, 2009)

3 Q-jets to make 1 good one? Well, I have 2 already....

I think I'll look into an Edelbrock, thanks guys.


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## 68greengoat (Sep 15, 2005)

I don't agree about the 3 to make 1 theory. All it takes is 1 good mechanic to build a properly functioning Q-jet. Just a matter of finding a mechanic who is a Q-jet expert....


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## 5spdgoat (Jan 28, 2008)

I had a Holley on my mildly modified 400 and HATED it. It was a 4150 (or 4160?) 750cfm vacuum secondary carb. I have a pretty healthy cam (236/242 duration @ 0,050") and the holley didn't like anything below 2000 rpm. I put the Qjet back on after doing some research on them, went up one size on the mains from stock, and she runs like a champ now. The Qjet is a very complicated carb, but it's really amazing. Great low rpm throttle response, great gas mileage and equivalent power to Holleys, Edelbrocks, etc. I saw nearly identical 1/4 mile ETs between the 2 carbs.

There's a reason GM used the Qjet for so many years. I think people are scared of it because it's a bit tougher to work on than Holleys, but it's so much better for street use.

Here's a great link to a bunch of websites that really helped me out.
All the QuadraJet Information I have found on the Internet
The "Quadrajet tuning" link brings you to this PDF file and it's awesome.
http://www.florida4x4.com/tech/quadrajet/qtune.pdf

-Jeff


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## jetstang (Nov 5, 2008)

A Holley 600 is not a dual line, and to a motorhead looks weak. Gotta go with at least a 650 to get the cool dual line carb.
I have Holley 750s on my Lemans and 90 454SS. It is a gas hog on the Lemans, 10 MPG. If you buy a brand new Holley, and your fuel tank is clean and good filters, the Holley carb will run perfect for a long time and look damn good. I had an Edelbrock on the 454, and putting the Holley on gained 20 HP, I dont' know if there was something wrong with the Edelbrock. Quadrajets are unbeatable if they are right, and run great even when they are nasty dirty, very forgiving carb. Best carb is a Motorcraft, Fords don't like maintenance, just ask my uncle.
In any carb swap, you must know how to work on carbs, because the 1st time something goes wrong you must be able to fix it. If not, you are going to be stuck on the side of the road.
Holleys have been a pain in the ass for years to me, now I have the money to buy new ones, Holleys are ultra reliable without incident right out of the box without tuning.


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## Rukee (Feb 8, 2007)

pfft! Holleys are the worse. I wouldn't want one on my enemies car.
I swear, buy a Elderbrock Durashine unit, it looks incredibly awesome and works perfectly right out of the box. The shine will last forever without polishing.


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## Petey D (Feb 14, 2009)

Thanks for the info guys, and for the links 5spd. Much apreciated.


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## jimmymike (Feb 26, 2009)

I just put a 750 cfm Eldebrock performer on my 69 GTO. It was no problem with the exception of throttle cable and mounting bracket info. I finally had to cut off the end of my stock cable and put a adjustable bracket on the end to mount it to the carb. I don't like the set up and I am concerned about my pedal travel..does not bottom on the floorboard and the cable coming out of the bracket is held in with a set screw. Any good advise based on your set up. I am new to the forum and it seems to be a great sight.

Thanks,

Jimmymike


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## VettenGoat (Jun 19, 2007)

You realize you'll need to either swap intakes or find (if they even still make them) an adaptor plate to allow for the difference in butterfly plates. (As I remember, a pre-66 Carter 4bbl intake would work in a pinch, but best to go aftermarket if you can.)
I ran a Holley 780 double pumper of my RA III back in the day and it performed very well throughout the rpm range and made monsterous torque. The heads were machined and cleaned up, and the distributor weights and ignition were dialed in. Also ran headers at the time. For a stock motor I don't think you'd want to go beyond a 650-700 cfm carb though. Never ran an Edelbrock carb, but they have a good reputation. Good luck.
Mike


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