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Discussion Starter #1
I have just replaced my Rochester QJet with a Holley 700 cfm, but I am considering rebuilding the QJet and putting it back on my 70 Chevelle SS454. I am an amateur just starting out with my first project and would like to know which of the two carbs would be the better performer. Also, who supplies the best manual for rebuilding the QJet. [email protected]

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I would suggest leaving the rebuilding of a quadrajet to an xpert my friend,,, I have tried many times to rebuild these carbs using an xpert an they only come out right about 1/2 the time,,, I use brand new ones on my restorations thats the only way to b sure that u get a good one,,,as far as performance I would rate the new 700 Holley and the QJ abiut the same,,, Good Luck L89SEDAN
 

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Djm, maybe it was just luck, but I rebuilt a bunch of Q-jets in my early years and never had a problem. I read a bunch of articles and books on them, although that was so long ago I couldn't reference them for you. It isn't that hard. I always epoxied the machining plugs found in the main body and usually ran #72-74 primary jets and "QQ" rods. I never really played much with the secondary setup. It really isn't that hard. Maybe one of our bros here at TC whose done a bunch in the last 20 years can update you. I always found the Q-jet to give me more mid range and part throttle response. ( read that torque) than a Holley. If you dial in the jetting and metering rods, you'll find they work as well, if not better, than a Holley. Read a book or two, spend the $20 on a rebuild kit and have at it.

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Discussion Starter #4
Gene Chas, I have found what you say about the difference in torque to be true. The QJ that was on the car when I purchased it in Sept was bogging when I layed on the revs in second and third gears. But the higher torque was there. I have noticed a pretty drastic torque reduction since installing the Holley. Since I have nothing to loose in trying my hand at a rebuild of the QJ, I am going to give it a shot. Thanks for the input. DJM

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For all around driveability, dependability and gas mileage, you just cannot beat a good QJ. If you are going to be using the car in a race mode all the time, then a Holley is better.

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DJM,

Yeah that's the same differnece I noticed 20 years ago when I was really into it. I like the Q-jet and you got my point, what's the risk to you, $20 bucks and a few hours. The one thing I never learned was the proper adjustments of the secondary "flappers". They're spring loaded and you can adjust the spring tension. You may want to toy around with these a bit to help solve your bog. I recall that if they're too loose its a bog situation and if they're too tight it a lack of power. But don't hold me to that. It was a long time ago I played around with these.
 

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Just dynoed a 406 small block a month or so
ago. Guess what the q-jet made more horsepower and torque than a 600 double pumper holley and an 800 double pumper. The
guys at the speed shop did not want to try the Q-JET because they said it was a waste of thime I proved them wrong. 375 horsepower
at 5000rpm and 480ftlbs of torque at 3500rpm
 

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Ah those GM engineers knew what they were doing! As a novice, I always thought the Q-Jet was a bit more elegant in design, but hey, Rochester is my home town.

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Discussion Starter #10
Hey guys, you have convenced me to rebuild that Qjet. I can hardly wait to get started. But I still need to find a good rebuild manual. Anyone got any suggestions?
 
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Doug Roe's book on Qjets is an excellent book for anybody serious about Qjets. There is more data in there than you will use, but lots of good info about parts and how to trick up the carb. If you get stuck just post and you will get lots of help.
 

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Discussion Starter #12
Thanks Wally. I will try and locate the book you suggested. I want to get started on this right away. I am anxious to get the Qjet back on and store the Holley as a backup. Thanks to the rest of you guys for your advise and input. I will let you know when I have my 70 SS454 Chevelle running with the Qjet again and also the trials and tribulations I may run into. Don't be surprised if you don't see cries for help on getting it right. Thanks again, DJ

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Come on Mike no sour grapes here. The Qjet won that one fair and square. I would buy your argument on the 600 but not the 800. 800 have jets that would envy the flow of Niagra Falls!
 

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Al right fellas, now it's getting interesting. I'm gonna put a Q-jet on my '67 while the 396 is still in it. My rebuilt 750 double leaks fuel around the front shaft ( thought it felt tight, guess I lost my touch)and I think the Performer RPM lets me mount a Q. I found a Caddy core for $60, I'll scrounge around a bit more( $25 sounds good!)I wish I knew how to definitely tell it's an 800, particularly if your only looking at one. That's why I'm looking at a Caddy.

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[This message has been edited by Gene Chas (edited 06-05-99).]
 

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Gene, I don't think a Caddy carb is more likely to be an 800 than others and Caddys typically have a real PITA throttle lever setup. I posted a piece last week with a short tip on how to see the difference, did you see that? I don't remember where or to who it was posted.

Tom
 

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Tom, yes I did, but it seemed looking down the venturi would be OK if I had two to compare. I guess that's the only way, huh?

[This message has been edited by Gene Chas (edited 06-06-99).]
 
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Hot damn, a test! That caddy carb can be made to bark at the moon. I like them because the fuel inlet is the same as the chevy. Use the big buick needle and seat as well.
 

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Hard to say... I love a well tuned Q-Jet and have used them on several of my cars. When they are tweeked and 100% you just can't go wrong. But I found that unless you are really prepared for the adventure, it's best to get a pro to build it. I had one built and basically the primaries are setup to be "polite" by sticking pretty close to stock, the secondaries though are improved somewhat. The bores have been milled out and the flapper's changed along with the jet's. Basically, the primaries are that of a stock 350 QJ and the secondries are from a 454... I am running that on my daily driver which is a 355cu/325hp with Stage-2 TH350 & 308 diff. I get roughly 20-25 mpg in polite but Hooaaa when I'm not polite. The daily driver is a 1980 Camaro.


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Assuming those GM engineers knew what they were doing, that's why the very high performance engines had Holleys. I don't believe LS-6's (and others) were equipped them because they performed worse than a Quadrajet.
 
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