Qjet

Heard a guy saying theres no such thing as a qjet 680,700 or 650. Only 750s and 800's.

That a 650 is just a 750 made to flow 650cfm.

Is this true.

 

...... I've successfully rebuilt my old edelbrock. How different is it to rebuild a qjet...
What can go wrong and why do most guys send out their carbs to get built.

 

no 650 Qjet. 750 800s,,, although the 800 is actually more than 800 cfm. that depends on want you did to your motor to make it draw more air.

If you did not know Pontiac put a 750 Qjet on a OHC 6 cylinder called a sprint (250 CI)

 

Thanks Bob. Looks like ill be using my carb off my 300sbb and throwing it on a 425 olds. What do you think about the rebuild question i asked?

 

answered Above....... plus other reasons.... Me I had mine rebuilt because I didn't have any automotive Qjets... Or even a rebuildable POScrape..

 

Replacing gaskets, and other basic kit components is pretty straight forward.
A true rebuild to make an old worn carb like new requires special tools that are not common for most technicians. You would want to put bushings in the base plate, replace the worn air valve cam and tension spring, recalibrate for todays fuels, and especially since you are talking about putting one from it original use calibration to a completely different engine. Quadrajets were made for a specific application, not generic like an edelbrock, so they don't typically move well from one application to another without recalibrations.

There were, for the most part, two castings on the primary side of the Quadrajet. One with larger ring can flow up to 750 cfm and the smaller ring is said to be capable of just over 800 cfm. There are many factors to vary the flow, such as throttle blade opening and secondary air valve opening. The Quadrajet, by design, provides correctly metered flow based on engine demand, up to the max.

 

What ring are you mentioning and ware do I find it? Is this something different than looking down the hole to see how much of a bump is in the hole. If that makes sense.

 

The smaller ring (larger casting) has the bump you are mentioning.

 

AHHh ok. so still have to look down the hole to determine size roughly.