Cliff's Quadrajet Parts and Rebuild Kits

General Category => Quadrajet Carb Talk and Tips => Topic started by: Bills64 on August 10, 2023, 11:13:08 AM

Title: Converting a 75 q-jet
Post by: Bills64 on August 10, 2023, 11:13:08 AM
I have a 75 Pontiac q-jet and was wanting opinions if it could be converted to the 77 style APT. I see the provisions to do so but didn't want to start in on it without getting opinions first. I know it would need the adjuster and power piston and block off the 75 version but anything else?
Title: Re: Converting a 75 q-jet
Post by: Cliff Ruggles on August 15, 2023, 05:10:26 AM
They can be converted but it still doesn't solve the basic flaw in the design.  Both jets share a common passage with the APT system.  Without completely blocking off the passages between them they never work as well as the later design.  I avoid those carb here, at least they are my LAST choice for building a custom high performance unit.  I've ran into enough of them over the years that didn't work well no matter what I did to they to learn to stay clear of them altogether.

The factory must have known about the issues and why they only saw a brief run back in 1975 and early 1976......IMHO.....