Thread: Holley or Q-Jet

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This is a question that may get asked frequently but I'd like to get it answered by someone who knows both carbs quite well and has used and tuned both. I know there is that group of people who absolutely HATE Quad-Jet carbs and do not even have a clue how to tune them and some that just know them inside and out and can get great performance and response out of them.
I almost went and bought a plain 4160 Holley 600cfm non-adj. float carb but then for some reason decided to hold off and do some more research.
This carb is going into the 63 Chevy II wagon that will be used as my daily driver. Right now the car has a 327 that will be used in it for a few months until the 350 is done but will eventually be used on the 350 with a 200-4r tranny.
What would you guys recommend here? I hear the Q-jet will get great fuel milage (some said 2-4 mpg more than the Holley or Edelbrock) and still have good performance. I still want decent performance when I want to get on it but again, it's going to be a street car (that can still smoke some ricers of course).

I'm not a fan of either, but a Q works better on a SBC than a Holley, probably because it was designed for the application. And yes, properly jetted, the Q will get better mileage as long as you stay out of the secondaries.

The thing about Qjets is they made about a million different models. Each one has specific differences egnineered into is many little passages.

However, I have always had pretty good luck with them, so i like 'em.

Right off the top, I ain't a "guru". I have rebuilt amd used my share of Q-Jets and Holleys, though, and in my opinion, for a responsive and economical carb in everyday use, the "right" Q-Jet is hard to beat. In original form, they were decent performers, but with blueprinting and tweaking by someone who really knows them insid out, they are outstanding. The small primaries give excellent throttle response and decent mileage when you keep your foot out of the secondaries, and those huge secondaries will kick you in the seat when you get into them hard. I have not had any experience with Holleys in many years, and their technology has definitely improved by many leaps since I used them in the late sixties and early seventies; then, they worked much better on the track in "romp and stomp" performance than on the street. They were just too coarse in their tunability; today, with the new metering blocks, adjustable floats, and the really great aftermarket blocks and bowls available, they are very likely equal to, and perhaps even better than an older Q. I think, though, that a well set up Quad would serve you very well; the thing you need to find is someone who truly knows his Q-Jets. I took my last one, after I had basically set it up - and it ran quite well that way - to a guy in my region, and the things he did to it were amazing. After he got it set up (re-set up, after my rough attempts) the performance of the truck was so much better it was amazing. They do work well when done right, and you don't have to keep tinkering with them. In fact, if tinkering is your thing, a Holley would be a better choice, I think - easer access to the "tinkerable" parts.

I'm going to 2nd what Rrumbler say's. I have used many Q-jets, and tuned them, and I have used the Holleys 65 & 75 spreadbores and I'll stick to the Rochester, if you get one from the bigger motors (Caddy) it should be a 850, if you need one that large. A Q-jet will support around 450-500 hp. If you get a used one with a soild float change it, it's most likelt gas logged and will sink.

Pat

for marine use the Q jet are very good abit better then the holley for mild use . a Q jet will take some dirt were the holley will not take any . less gaskets for the Q jets. but it was EZ to get tune up parts for holley jets power valves etc over the Q jets. that is why alot of guy went to the holleys .i like the themo quads the Q jets will get good milage .like other have said. if you keep your foot out of the back door GOOWAAAhhhh they sound some thing like that when they hit

Originally Posted by FMXhellraiser

This is a question that may get asked frequently but I'd like to get it answered by someone who knows both carbs quite well and has used and tuned both. I know there is that group of people who absolutely HATE Quad-Jet carbs and do not even have a clue how to tune them and some that just know them inside and out and can get great performance and response out of them.
I almost went and bought a plain 4160 Holley 600cfm non-adj. float carb but then for some reason decided to hold off and do some more research.
This carb is going into the 63 Chevy II wagon that will be used as my daily driver. Right now the car has a 327 that will be used in it for a few months until the 350 is done but will eventually be used on the 350 with a 200-4r tranny.
What would you guys recommend here? I hear the Q-jet will get great fuel milage (some said 2-4 mpg more than the Holley or Edelbrock) and still have good performance. I still want decent performance when I want to get on it but again, it's going to be a street car (that can still smoke some ricers of course).

Shawn -

Here is part of a discussion I took off of another forum probably a couple of years ago. I can't comment on whether these guys know their stuff but it sounds like they might.

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"About the Q-jet, yes it's wise to be wary until you know the reasons why people don't like something. When the Q-jet first came out, the initial reason was because it was way, way more complicated than a Holley or Carter (kind of like people who hated EFI when it first came out, it's different and seemingly complex). Over the years as these Q-jet equipped cars continue to run untouched for 15, 20, 25, 35 years, the carb, after time, gets way past the point where it needs an overhaul. This is where the names "Quadra-junk" and "Quadra-bog" came from, because a carb is obviously junk if it doesn’t continue to work perfect after 20 years of service. These same people don't call Holleys junk when they find an old worn out one, they just overhaul it, like it needs.

In addition, the Q-jet (like anything else) has a few minor issues that get worse over time, but are easily corrected. The main two that come to mind are the fuel plugs on the bottom of the main body, which tend to leak fuel into the intake manifold and cause a variety of problems; and the throttle shafts, which tend to wear out causing vacuum leaks, but can be fixed better-than-new with brass bushings. Also, ignorant mechanics tend to torque the carb bolts down to the same torque as their head bolts, which warps the carb and causes fuel leaks, etc.

The guys that really know and understand the Q-jet are the ones that love them."

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"On the subject of “Quadra-Junks”- one of the other reasons has to do with the fact that GM spent a lot of time getting just the right tuning for each type of engine. One tune for Chevy 350, same carb-different-tune for Buick 350, 455, etc. So Jo Backyard needs a carb for his sbc and grabs a "good" one off his brother's Olds. Since it was not factory tuned the same as one for his Chevy, it won't run quite right."

Maybe this can explain why some people love the Quadrajet while others seem to absolutely hate them.


Jim