QuadraJUNK
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
CARBS Tests HP/TQ
A square bore carb should be sized properly to the engine, so many sizes are offered.
The GM solution: Q-J. The spreadbore has small primarys which allow velocity, response & fuel economy while the huge sec. provide capacity. The cfm rating of what it is capable of is not relevant on smaller engines- it works well because of the small primarys.
The Q-J is basically GM’s one size fits all V8 carb & notice how many different 350s from GM came out after the Q-J ...
CARBS Tests TQ/HP
http://www.corvettefaq.com/c3/carbcomparo.htm
While we could do w/o the Quadrajunk comments, some of the Q-J fans comments are as bad...
The Holley was designed to be a perf. carb.
The GM solution: Q-J. The spreadbore has small primarys which allow velocity, response & fuel economy while the huge sec. provide capacity. The cfm rating of what it is capable of is not relevant on smaller engines- it works well because of the small primarys.
The Q-J is basically GM’s one size fits all V8 carb & notice how many different 350s from GM came out after the Q-J ...
CARBS Tests TQ/HP
http://www.corvettefaq.com/c3/carbcomparo.htm
While we could do w/o the Quadrajunk comments, some of the Q-J fans comments are as bad...
The Holley was designed to be a perf. carb.
Le Mans Master
Joined: Oct 2007
Posts: 7,440
Likes: 962
From: Tennessee/Rhode Island
Check out my dyno sheet under my recent post about my L-82 first time on the dyno with the Holley 4175 carb which has the A/F ratio graph half way down the first page of the post. The holley 4175 was pretty much dead on below 3,500 RPM and then leaned out slightly up to 5,500 RPM, but just slightly.
Race Director
Joined: Apr 2000
Posts: 17,672
Likes: 199
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Q-Jets have been called many names over the years, and beeing out of production for years now, tuning parts are getting harder to find. While Holley and Carter parts are easier to find, bettin' you'll be looking at distant fading tail lights of well set up Q-Jet car on the street.
Advanced
Joined: May 2008
Posts: 81
Likes: 0
From: Annandale Virginia
Some Quadrajet links for part I found while tuning mine should you decide to go that route. I went with Cliffs.
http://www.carburetion.com/quadrajet.asp
http://www.cliffshighperformance.com/parts.html
http://quadrajetparts.com/
http://www.carburetion.com/quadrajet.asp
http://www.cliffshighperformance.com/parts.html
http://quadrajetparts.com/
Mike
Melting Slicks
Joined: Apr 2002
Posts: 2,337
Likes: 14
From: Norfolk VA
My guess is that theyre so many parts to it that it would take much more time to get it set up properly between races. But you see not everyone drag races. Properly tuned it performs just as well as a Holley. People should take the time to learn to properly set them up and tune them and I bet the name calling will be to a minimum.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
The implications here are all over the place.
GM did calibrate a few Qjets for high performance in the early years, mostly on Pontiacs and Buicks, while the Chevy line used mostly Holley.
Later Qjets were calibrated primarily for emissions while AFTERMARKET Holleys were designed for performance.
That is why most Holleys and variants are also labelled "For off road use Only"
I don't know why this is so hard to understand. Apples and Oranges.
It's no different than turning an oem L48 160hp into a 350hp sbc.
That's not to say that a Qjet cannot be rather heavily modified (not just tuned) to perform comparable to an AFTERMARKET performance carb.
Cliff Ruggles has been backlogged for many years for these modifications at any given time of anywhere from 4 months to well over a year.
Not the kind of work your average carb rebuilder or carb tuner does.
GM did calibrate a few Qjets for high performance in the early years, mostly on Pontiacs and Buicks, while the Chevy line used mostly Holley.
Later Qjets were calibrated primarily for emissions while AFTERMARKET Holleys were designed for performance.
That is why most Holleys and variants are also labelled "For off road use Only"
I don't know why this is so hard to understand. Apples and Oranges.
It's no different than turning an oem L48 160hp into a 350hp sbc.
That's not to say that a Qjet cannot be rather heavily modified (not just tuned) to perform comparable to an AFTERMARKET performance carb.
Cliff Ruggles has been backlogged for many years for these modifications at any given time of anywhere from 4 months to well over a year.
Not the kind of work your average carb rebuilder or carb tuner does.
Safety Car
Joined: Oct 2000
Posts: 3,593
Likes: 103
From: Southern Indiana
Because I have done it and that why I have my opinion of whats better and easier.
Safety Car
Joined: Oct 2000
Posts: 3,593
Likes: 103
From: Southern Indiana
People should take the time to learn to properly set them up and tune them.
If you have to buy a $20 book and search for parts for weeks it kind of takes out the "fun" factor.
Run a quad until it breaks and throw it in the corner and get a Holley = drive and be happy!
Burning Brakes
Joined: May 2008
Posts: 1,116
Likes: 5
From: Middleburg Florida
Doesn't take a 4 year degree, and once you learn them it's not a big deal. The biggest difference is that the Q-jet has three circuits vs. the Holley and others that have two and because of that have more variables for tuning. You can find all the parts you need at a couple of websites, Cliff's is one of them. It's like everything else, just a choice. As for racing, there are some guys running Quads, but the majority are probably running something else that's more designed for racing. As most of us don't drive the same of the street as we do at the track, so IMHO that's comparison doesn't make sense. Think about it, at the track how much time do you spend in the cruise range of a carb? It's basically idle and WOT...
Drifting
Joined: Dec 2004
Posts: 1,714
Likes: 42
From: Austin Texas
Blitz72,
Do you feel your original question was answered? Did you know carburetors could create such a maelstrom of debate?
I noticed your original issue is with the choke. What type of choke does your qjet have on it now? Perhaps there is an easy fix.
John
Do you feel your original question was answered? Did you know carburetors could create such a maelstrom of debate?
I noticed your original issue is with the choke. What type of choke does your qjet have on it now? Perhaps there is an easy fix.
John
Race Director
Joined: Apr 2000
Posts: 17,672
Likes: 199
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
If anyone thinks a Holley is easy to tune then explain to me what high speed air bleeds, idle air bleeds, emulsion jets, power valve channel restictors, idle feed restictor, air hole size, transfer slot restrictors, do. And what effect they have on the tuning of the carb if you go up or down on the size and if you change one thing should you be changing another ?
This is of course off the top of your head without looking each one up on google.
Anyone who spent 2 years in grade 9 can change a jet size you need grade 10 to start playing around with idle mixture screws
I have a 825 Drag Race Demon on my 427ci and it runs perfect and I get 24 mpg on the highway
This is of course off the top of your head without looking each one up on google.
Anyone who spent 2 years in grade 9 can change a jet size you need grade 10 to start playing around with idle mixture screws
I have a 825 Drag Race Demon on my 427ci and it runs perfect and I get 24 mpg on the highway
Melting Slicks
Joined: Feb 2006
Posts: 3,428
Likes: 5
From: Japan
There seems to be a QJet crowd and a Holley crowd on this forum. QJets are popular with C3 owners I think because of the limited hood clearance issue (That's why I've kept mine) but for ease of tuning, no-waiting seconday opening, bowl capacity, and several other reasons Holleys have it all over the Rochester. It is true that you can tune a QJet to work very well on a well-tuned, high-performance small block but it's still essentially a vacuum secondary (read:delayed response) carb that is fiddly to work on even on the best of days. If I want to change a power valve or jets on my Holley all I have to do is pull off the float bowl and do it. Try that with a Quad and I have the whole carb scattered all over the workbench for a couple hours and it's a miracle if it goes back together right the first time with no leaks and the choke still working right. That's why Holleys are always gonna be the favorite of guys that like to tinker with their cars and why NASCAR has continued using them into the 21st century...they just work.Problem is, they don't fit under a C3 hood very well...
