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. djssaab@msn.com

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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

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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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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I have a new Edelbrock Q-Jet on my 69 396 EC. I took about two weeks to settle in, it's a weekin car, now it work perfect.

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.

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

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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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?

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.

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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the quadrajet was probably jetted a little better for that particular engine...


Mike

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!

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).]

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

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).]

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.

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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The proud owner of a Hot Canadian 64-SS.
ZZ4 Powered with real attitude ! :)
Chevelle Tech Gold Member

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.

How do you change the "jets" on the secondary of a Qjet??

I think that guy is a snake oil salesman. There are no jets to change. The holes in the floor of the secondary are .135 and all you need do is change the rods and the hanger to increase fuel flow, the rods, and the timing of the flow, the hanger. I have done lots of Qjets, and Doug Roe has done some trick ones for me, no jets in the secondary.

Wally, I had no idea you are Dr. Q. Do you have any cores laying around the shop? I'm planning on putting the car on the road this weekend. I'd like to have a replacement carb by next week. I can't really honk on it too hard, the motor's new and I want it to stay in one piece because it's for sale.

Wally, some of the big carb shops knock out the sec jets, thread the holes and install screw in jets. Big waste, IMO.

What I thought was odd was the reference to 350 primarys and 454 secs, there's no difference between the two, I wonder what they really did?

Gene, if you get really hard up for a core, I've got some, could even build one but not next week, I've actually gotten started on my own 406 and it's going first. Everything else is going on hold til that thing is together. Finally.

Tom

Gene, I have the 67 core that came on my 67 327 car. I think I can round up a Mercrusier Qjet as well, let me know.

Tom and Wally, I just rang the wrecking yard down the road from me ( Monday AM) and they're gonna scrounge around and see what he can dig up. Funny, the guys asks, " What is it you want to do?", like I had something up my sleeve. I told him I wanted to put in on a 396 but I wanted the BIG 800cfm job.. He said he may have one off a Pontiac 455. I may end up running this Q on the 427 'cause I'm running out of "fun money" and the three annular discharge 2bbls for the TRI are $235 a pop. OUCH! And I have a stock Chevy alum rect port manifold. DJM are you still paying attention to all this gobble-de-gook? I'll rebuild my QJet THIS WEEK, if I can find the core and a kit. Stay in touch. Oh, buy some plumbers epoxy or similar stuff because we are going to patch up the machining plugs with epoxy to make sure they don't leak. And Wally, how in heck am I going to dig up a Buick needle and seat? It may be hard enough to find someone who stocks the rebuild kit for whatever core I get.

[This message has been edited by Gene Chas (edited 06-07-99).]

Gene here in southern calif, you have to wade through a sea of quadrajets just to get to the parts cars.. if you really cant find one let me know..

Mike

Well put on you hip boots and find some of the early ones, 68 to 73 chevy types. They are easier to work on, fully adjustable without hacking the base plate. It would be nice to have a backup for the 71.

Hey Gene Chas. Yeah, I'm still listening. I am ordering my rebuild kit from a small time race shop here in Maryland. I was ordering today, but didn't have the number and after verifying the number with the numbers book, I discovered that it is a Carter-built Rochester, manufactured in 1971. The motor in the SS is a '71 454 engine, which was put in the car before I bought it. According to the book, the Carter-built Rochester 4BBL was not used on the 70 454 motor and I believe that some horsepower was lost in the transition from 70 to 71. Correct me if I'm wrong.

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Wooooaah! Quadrajet overdose! Quadrajets work real well... when they work properly. Between the two carbs in question, it's a toss up in my opinion. I prefer Holley's for the big horsepower stuff, but the Quads work well in relatively mild stuff. I know the Quads can be massaged to make good power, but I like the simplicity and power potential of the Holley. A 3310 Holley would probably be better than both of carbs you mention DJM, but I know that's not the question. The Holley is cheaper and easier to rebuild than the Quad... for me.

Aw Glenn, we're just trying to give that much maligned carb some positive spin! Both DJM and I have Holleys on now. He a 700 and I a 750 dbl. We'll see what thenperformance differential is. DJM I know nothing of Q-jet history adn power levels. Heck I thought they were all made in my home town - Rochester I am saddened to hear that's not true. Naw, it doesn't really matter. If you really want one that was original on the '70 54 I know a fella the next town over that's up to his armpits in 'em - for a price. I may be paying that price soon because the local yards aren't kickin' up the Q I'm looking for.

Hey Fellas, I got that rebuild kit today. The distributor messed up and sent a Holley manual, instead of the kit. Wally, I found that Doug Roe book. I can hardly wait to start tearing that thing down, but first some book learnin'.

Gene Chas, after I posted my last reply about the history of the Rochester/Carters, I discovered that the 71 Qjet actually produces 5 more HP than the 70 Rochester. I think I will stick with the 71!!

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DJM- Good luck on your endeavor! I never had much luck rebuilding q-jets, glad I have a bud in the auto biz that can.
There were more differences between the 70 and 71 LS5 engines than just carbs. 71 saw lower compression VIA open chamber heads, cam timing changes, and the way the engines were rated also changed.
I did like the way my q-jet ran on my '70 LS5 car when I got it dialed in.

If Gene gets the Qjet hitting on the 27, he will throw stones at the Tri setup and double the range of the car, from 4 to about 8 mpg, a vast improvement!

Wally
Gold #67

Yeah, Yeah, Yeah... Quadrajets are the greatest! they're the best! nothing works like a Q! Spanks ALL carbs.! Geeeez, you guys are KILLIN me! DJM! The shop didn't make a mistake! Read the book they sent! If I read any more of this Q stuff, I might start believing it myself! http://www.chevelles.com/forum/wink.gif

By the way the 1970 and 1971 Chevelles had their horsepower measured the same way on an
engine dyno. They did not have net figures until 1972 Long live the Q-jet. No power valves to blow. The metering rods are easy to change in the secondaries no mess. The only reason those 780 Holley's were on those engines were for Grumpy Jenkins to spin the motor to 7800rpms or better.

Glenn, don't let this get around, but I have a secret plan to achieve World Peace and Botherhood of All Mankind by using Q-Jets in a low polar orbit. Email me for all the details.

Tom (remember, keep this quiet. If it gets out too early it may cause rioting in some of those backward countries that don't have any Q-Jets)

Tom, already been done! A Qjet was on the Lunar Lander, little known fact. Yep, used it to land the thing, much better low end response, clean idle, sat that baby right down, no problem. If that had been a Holley, they would have been a big grease spot on the moon, we could have had a new crater to name, The sea of Stumble!

Other than the considerations for world peace and order, my tri will have three HOLLEY carbs on top. Sorry Wally, the '27 deserves 'em.

Gene Chas
Gold #62
'67 SS427

Mr. Kent, doesn't this make you want to puke.

[This message has been edited by Gene Chas (edited 06-15-99).]

Geez, this thread is getting so long I'll have to check at work through the cable modem.
Wally, I found you're lunar carb today. Rummaged through shelves and shelves of carbs today after work. Picked out one 72 cady that had the bigger primary bores but decided on one from a '70 Cady which looked real fresh and had a "rebuilt by Holley" sticker on it. How ironic. I couldn't resist.
It has a "lunar antenna". Directly opposite from the accel pump there's a T protruding from a hole, sprung. It's the lunar model! that must be a vent, but it's the most unusual I've seen. Looks like an antenna.
Unfortunately it has the smaller primaries. The smaller ones look as if they're bushed, compared to the others.It's a #7040230 and the rebuild kit is only $11. Total cost = 65. This one probably won't flow the 750cfm the Holley in my comparo does. I'm breaking in the 396, and for that, the Q-jet will give me much smoother low to mid range rpm and that's were that motor's going to be for the first 800-1000 miles or so.

When I'm done with it. I'll post it here for $65 + shipping n pass the good deal along to a member.



[This message has been edited by Gene Chas (edited 06-16-99).]

Sorry I couldn't respond sooner. I couldn't get on the Web. The server said it was cosmic interferance caused by "SPACE JUNK" in the polar orbit, blocking the sattelite downlink. I hate to burst your bubbles guys, but I was the first to launch a Q-Jet in to orbit. That's right, I threw a Q-Jet so hard one time, it went straight in to orbit. I like your idea Tom. What better place for a Q-Jet? We could round up the millions of angry Q-Jet owners and have them fire their carbs right in to space. It would save millions in launching fees and just think how happy they'd be once they're rid of their frustration. Talk about world peace! Tom, you're a geeeenyiss! How can I keep this a secret? EVERYBODY! Throw your Q-Jet in to orbit! Free at last! free at last!

If you are going to all that trouble, throw them in a low polar orbit, so when it decays it may have a chance of whacking the Colt Industries plant in Bowling Green Kentucky, where the make the "H" word carbs!

I've heard enough on the Holley vs Qjet. The best Qjet if you can still find them were from the 68 Chevelles. If your car came with a Holley then I'd run with it. Can we please move on now.

Mark

Hey Mark, this is kind of like TV and Radio, nobody is twisting your arm to read the posts under this thread, and for your infomation the best Qjets came on 1970 Cobrajet 429 FORD Torinos, how you like them apples?

Wally
Gold #67

Wally, no S*$*, I just saw that under applications in my rebuild instructions,
396 chevy, 427 chevy, 429 ford. What the...

Ironically, the carbs I may end up using on my tri power are a Holley HiPo version of an Autolite 2 bbl. Autolite, Motorcraft,FFFFFFFF

I love 'em all!

COPO, dont bust our balz when we hit 50.

In Doug Roe's book, he has some stuff on thet ford carb, it is bad! They did all the tricks, drilled the pickup tubes, big needle and seat, machined the fuel well, kool stuff.

I switched back to a Q-jet on my 350. The Q-jet is a good running carb except if the car sits for a week its hard to start. The holly carb always started even after the car sat for a long time. The Q-jet is a rebuilt. I get more MPG with the Q-jet.

This is like one of those MAC vs PC or CHEVY vs FORD debates. it will never end because some of you still think quadrajets are good carbs! http://www.chevelles.com/forum/biggrin.gif

LONG LIVE HOLLEYS AND TEAM CHEVELLE


Mike Reeh
Gold #34

DJM, check "Tips and Fixes", I just posted some comments about my junkyard Q-jet rebuild.

I think I get a duel carb manifold. Put a holley on front and Qjet on back.I'll have it all..good gas mileage,stumbling,simplicty,complexity......etc,et c....

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JoeS
"67 Malibu"

Well gentlemen, we needed to hit 50 posts just to PO COPO so I had to post #50.Take that Mark!~
I'm gald to hear some folks still use the old Q. There's nothing wrong with Holleys, and heck, I'll be using Autolite knock-offs on my 427 TRI. Blondes, brunettes, redheads, black,white, it's outta site, I LOVE 'EM ALL!
Have I mentioned my idea to use 3 2bbls TBI's on my tri......

First day of summer, happy crusin'.

Just drove our 67 chevelle ss down to Pigeon Forge with 373's in the rear and 396 4-speed.
That Q-JET got us about 14 mpg at 3400 rpms at 70mph from Dayton, Ohio. The 750 vacuum holley got about 10mpg. Had a lot of fun driving down I-75 had to put a couple mustangs down. I had to let off of it at about a 110mph but they kept going. The show
was pretty good down there. Will be going to the Grand Run on Sept. 17&18 next. That Q-jet really pulls when those secondaries go.

Guess what! The one who started this long thread is back and is working on the rebuild. Gene Chas I read the tips you posted and printed them to hang over the old work bench for reference. Once I tore into the thing, I found it is not as complicated as I thought. The worst is yet to come; getting it back together and getting it to work. Anybody out there living in Maryland going to the Chevelle/El Camono show in Northeast this weekend?

Hey Wally, you and Mr. Bill are MD boys?