Quadrajet tuning success - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum

Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
lost password?   |   register now

LinkBack Thread Tools
  #1 (permalink)  
Old 04-07-2010, 03:12 PM
Mertz's Avatar
Registered User
Join Date: Jun 2002
Location: Reardan, WA
Posts: 702
Wiki Edits: 0

Thanks: 1
Thanked 5 Times in 5 Posts
Quadrajet tuning success

I just wanted to give everyone some information about my attempts to get a quadrajet running on my 72 Chevy truck with 350 and 350 auto. First you should know that Cliff Ruggles has been helping me solve problems and has been very willing to email me with answers to all my questions. I have both his and Roe’s book but find his more helpful.

First thing I learned was to check the carb you are using for the original jets and rods. You can find this on several web sites if you have the carb number. The next and most overlooked is the size of the air bleeds and how many air bleeds the carb has. Large air bleed carbs require larger jets. I started this project with what I thought would be an easy bolt on and go. I found a Jet Performance Stage II carb in almost new condition. The guy had it on a Dodge pickup with a 318 and took it off to sell the truck. I don’t believe it ever ran well on the truck and that is why he took it off. The carb number showed it came off a 77 Corvette and should have 77 jets and 52 rods and had large air bleeds. It actually came from Jet with 73 jets and 43 rods (a pretty standard combination). I put it on the truck and stomped on it and it fell flat on its face. I tried a number of things but could not get it running right (not too much help from the Jet tech line). I finally switched to another carb I had but one I could not find the specs for. I ended up putting in 71 jets and 43 rods. By this time I got my Innovate LC-1 installed. After running it and checking the mixture on the computer I found it was running very rich. I changed to 64 jets with 43 rods and got it to lean out but now it was too lean so I went to 66 jets and have it running at about 13.5 at cruise, a little rich at idle (12.8) and 12.8 or so at WOT. It is leaning out a little when I get on it at cruise so I am going up to 68 jets. I have a carb with an APT that helps fine tune the mixture. If you are looking for a good tunable qjet get one from after 1975 but before they went electronic. These will have the APT for fine tuning the A/F.

The long and short of all this is that the truck has never run better. It had an Edlebrock 1406 on it when I got it and it ran fine. I just wasn’t satisfied with the power and the fuel economy. I can now spin the big tires from a stop and am getting 16+ mpg in a ¾ ton truck with highway gears. Best mileage with the Edelbrock was 14 unless I was running premium gas and cruising on flat ground. I think I can still do a little better than 16 with the final jet change. My goal was 18. I can now tap the gas a little and it launches. Some have said a well tuned qjet is better than EFI and I can now say that I believe it. And there is no better sound than when the secondarys kick in (there goes the gas mileage).

Reply With Quote Quick reply to this message
The Following User Says Thank You to Mertz For This Useful Post:
Bratzler (07-25-2013)
Sponsored Links
  #2 (permalink)  
Old 04-07-2010, 03:31 PM
DoubleVision's Avatar
Not Considered a Senior Member
Last photo:
Join Date: Oct 2002
Location: Heart Of Dixie
Age: 43
Posts: 10,733
Wiki Edits: 0

Thanks: 19
Thanked 77 Times in 71 Posts
Hard to beat a Quadrajet once you got it right. With the right combo they give killer sensitivity and great mileage. When the secondary`s come in the classic sound they give sounds like it`s going to suck the hood in.
Reply With Quote Quick reply to this message
The Following User Says Thank You to DoubleVision For This Useful Post:
Bratzler (07-25-2013)
  #3 (permalink)  
Old 04-07-2010, 03:46 PM
Hippie's Avatar
Analog man in a digital world.

Last journal entry: HEI comparison.
Last photo:
Join Date: May 2003
Posts: 2,253
Wiki Edits: 0

Thanks: 3
Thanked 5 Times in 5 Posts
I love it when a QuadraJet comes together.
Reply With Quote Quick reply to this message
The Following User Says Thank You to Hippie For This Useful Post:
Bratzler (07-25-2013)
  #4 (permalink)  
Old 04-07-2010, 03:50 PM
richard stewart 3rd's Avatar
Registered User

Last journal entry: 351W rebuild
Last photo:
Join Date: Jan 2006
Location: tremont, pa.
Age: 72
Posts: 2,263
Wiki Edits: 0

Thanks: 26
Thanked 33 Times in 31 Posts
I like Qjets, if other guys knew how well they perform, they
would learn how to tune them instead of buying after market
Reply With Quote Quick reply to this message
The Following User Says Thank You to richard stewart 3rd For This Useful Post:
Bratzler (07-25-2013)

Recent Engine posts with photos

Quick Reply

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Please select your insurance company (Optional)


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
acceleration flat spot in carb. corvettetonybone Engine 17 04-13-2013 08:31 PM
Demon Tuning by cuda66273.... mstngjoe Engine 4 03-13-2006 06:46 AM
Success in tuning BG Speed Demon 406chevelle Engine 2 06-26-2005 09:44 PM
what first? advance curve or carb tuning? dirtydave Engine 3 11-07-2003 04:42 PM
Quadrajet tuning Problem????? cooterks Engine 2 11-25-2002 12:22 AM

All times are GMT -6. The time now is 01:50 AM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.