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Old 08-03-2012, 10:02 PM
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Quadrajet to Holley

I have a mild Chevy 350 in a 28 Nash street rod. The carb on it is an OEM Carter built quadrajet. Performance is lacking. It runs ok, but I know it should run better. A trusted friend reccomended I scrap the quadrajet and put on a Holley 650 with mechanical secondaries. The car has sat for a while so I had planned to rebuild the carb anyhow, but if I'm better off with the Holley, then I'll go that direction. My question is, is it a straight swap? Will the Holley fit on the same manifold (it's and Edlebrock manifold)? Is it as simple as going to the auto parts store buying a carb and bring it home and slapping it on? (Then fine tuning I'm sure) if so, which Holley to I want they seem to offer a million.

It may seem like a silly question to a lot of you more knowledgeable folks. I've been a motorcycle mechanic my whole life and have some boat engine experience, I have the mechanical abilities and the tools, I just have very little experience with carbureted small block Chevy engines.
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Old 08-03-2012, 10:12 PM
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I like Holleys but if I were you I would send that Q-jet to a performance Q-jet rebuilder with your specs and let him do it. Just switching to a Holley won't cure you problem plus it won't fit on your spreadbore intake w/o an adapter.....and the adapter is a no-no. Do a search on this forum for "Q-jet rebuilders" or "Q-jet help"
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Old 08-03-2012, 10:22 PM
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You think getting the Q-jet rebuilt would be a better solution than swapping for a Holley? I'm not trying to save money here, I'm not wealthy, but I want it right. If a new manifold and and carb are the right solution, I'll go that way. But if paying a proto rebuild the Q-jet is the way to go, I can do that as well, however, I do prefer to do everything myself.
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Old 08-03-2012, 10:27 PM
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Yea I would stick with the qjet and get familiar with it.
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Old 08-03-2012, 11:36 PM
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The Q-jet, when properly rebuilt and tuned for the application, is one of the best carbs ever designed and built. Problem is, most have no idea how to properly rebuild them or adjust them. Just replacing gaskets, float, seals, etc. , wont return your q-jet to its proper form.(I also suggest sending it out to a Q-Jet Pro) The q-jet will offer better idle quality, off idle response, full throttle power, and the best possible economy of any factory carb.

There are cars out there knockin down 25mpg, others running 9 sec ET's, others pulling huge loads with big block trucks, all with a Q-Jet. There are only 2 sizes of Q-jet, 750 or 800cfm, yet they can be tuned to work on anything from Chevy and Olds 307's to big torque Buicks and Pontiac. From grocery getters to Super stockers.

My first suggestion would be to pick up Cliff Ruggles Q-Jet book, its current considered the best Q-jet book available. Check Amazon or here:
Cliffs High Performance Quadrajets :: Qjet Carburetor Rebuild Kits, Parts, Quadrajet Rebuilding, Quadrajet Parts, Bushing Kits, Carb Tuning

Read it a couple of times, then decide if you want to tackle the rebuild/mods yourself, or send it to a Q-jet pro.

Good luck with your decision
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Old 08-04-2012, 12:42 AM
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are you sure your issues are all carb related and why? holley makes soread bore carbs BTW
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Old 08-04-2012, 07:12 AM
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Q jet is one of the best fuel mixers commonly on GM, another would be the carter AVS found on many mopars. Cliffs book is the good way, and will identify what you have. my library can get these type books, and there are tons of women there. After camming up, my q jets had drilled idle ports, and quicker vacuum break pod timing to open the secondaries, the G hanger , rods. They call them quadrabogs when the secondaries just flop open from too much secondary pod.
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Old 08-04-2012, 08:54 AM
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Quote:
Originally Posted by vinniekq2 View Post
are you sure your issues are all carb related and why? holley makes soread bore carbs BTW
I realize I could have other issues, but I'm playing a hunch. The car has sat for a while. That usually means the fuel varnished to some extent, and I'm sure we've all seen what that can do a million times. I had planned to rebuild the carb just for piece of mind when my friend reccomended I toss the Q-jet and put on a Holey 650 spread bore. So I just figured I'd run it by you gurus.

I did find one problem. I had guessed my secondaries might not be opening. So after some research here and other places, I found that there is a little latch on the Q-jet that prevents the secondaries from opening while the choke is on. On my carb, that little latch appears to have been installed improperly. It just hangs there and never moves out of the way when the choke turns off, so it was preventing my secondaries from opening. I wired it out of the way, and the car runs better. But I still feel like the upper flaps aren't opening. When I first started poking around, they were stuck slightly, like they hadn't moved in a while. So now I'm going to check for vacuum issues.

I'm learning as I go here.
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Old 08-04-2012, 09:20 AM
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Get the book, it will set you right. Help you return to proper function so you can tune it with out having to deal with a previous hack repair.
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Old 08-04-2012, 09:40 AM
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Thanks guys. I ordered the book.

Although, I have to say, I'm a little surprised by the responses. I figured most folks were going to tell me the Holley is the better carb and to go that route.
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Old 08-04-2012, 09:53 AM
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The secondary top stuck when you tipped it in? That will do it.

Yes, the throttle shaft is gunked up. You can clean that. This so common, yo show remove the carb top and soak it. The screws holding the butterfly flaps on the shaft can be so tight thats it bends the shaft slightly causing this. Possible, not likely. Once the choke switch position or bend is fixed that will not be a problem.
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Old 08-04-2012, 10:04 AM
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The secondary top stuck when you tipped it in? That will do it.

Yes, the throttle shaft is gunked up. You can clean that. This so common, yo show remove the carb top and soak it. The screws holding the butterfly flaps on the shaft can be so tight thats it bends the shaft slightly causing this. Possible, not likely. Once the choke switch position or bend is fixed that will not be a problem.
Yes. Not bad, I didn't need a crow bar to free it or anything. But when I moved it by hand, it had a little stick to it. Like it hadn't moved for a while. Once I moved it, it freed right up for the entire range of its travel. I assume if it moves freely, then the upper flaps are functioning correctly, right? There isn't a vacuum line to open the upper flaps that I can see, they appear to open once the secondary butterflies open and air begins to move past them. They are hooked to a little vacuum puller, but that looks like its made to close them, not open them, another choke bypass maybe?
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Old 08-04-2012, 11:38 AM
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The q-jet has a gazillion pieces in it. It really is a good carb if you have the time to learn it,,,,or,find a local super stock racer that uses a q jet,make a minor sponsorship to his car and I guarantee he will make your q-jet into a fabulous street carb with little tweeks you wont know about until you rebuild a few or he shows you.
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Old 08-04-2012, 12:16 PM
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It's funny that you guys like the Q-jet so much. Every time I take it anywhere the first thing other car guys notice is the carb. I took the car to lunch today and a guy looked the car over for maybe 15 seconds and said "Nice car, but you got to get rid of that Quadrajunk and put a Holley on there." that must be the 5th or 6th time I've heard that in less than a week!
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Old 08-04-2012, 12:55 PM
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Quote:
Originally Posted by nitsuj View Post
It's funny that you guys like the Q-jet so much. Every time I take it anywhere the first thing other car guys notice is the carb. I took the car to lunch today and a guy looked the car over for maybe 15 seconds and said "Nice car, but you got to get rid of that Quadrajunk and put a Holley on there." that must be the 5th or 6th time I've heard that in less than a week!
those are all people who had one get out of tune and had no idea how to fix it. When I was young I was the same way, just bolt on a holley. I can tune a Holley with one eye tied behind my aching back.
For the Q-jet, I needed some help. On a car that see's a lot of cruising, the Q-jet is fantastic, great part throttle response, the best mpg this side of an EFI unit.

I used them on wagons, 4x4's, stockish muscle cars, anything thats built mainly for street use.

Even the Holley spreadbore carbs. need tuning, and wont get anywhere near the mpg that the Q-jet can pull down. They will make the car seem faster, but for the cost you can get your Q-jet professionally restored and calibrated for your motor.
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