The Stovebolt Site Forums The Shop Area The HiPo Shop Quadrajet -- jetting for 350sb

Calling all Quadrajet gurus...trying to set up a 750cfm qj on mildly modified 350..10:1, mild cam(15" vac),turbo 400..stock conv.,3.08 rear..sugestions for jetting/metering rod/hanger. Ran pretty good with 600 Holley with out of the box jetting.

Simple question, but a VERY involved answer.

Rochester made 100's of different quadrajets set up for different applications. These have many DIFFERENT airbleeds.

One would need to know the EXACT quadrajet you are trying to use to come close to a recommendation.

There is now an excellent book (also very inexpensive) on the market concerning the modification of quadrajet carburetors by Cliff Ruggles. Publisher is SA Design. Check your local bookstore.

Very best book on carburetors for the lay mechanic that I have read in 45 plus years of working on them.

Jon.

Jon, thanks for the reply. Carb # is7045589('74-'77 CA Chevy/GMC).I have Ruggles book on order...been studying Doug Roe's Rochester Carbs(HP Books). Reduced the tension on the secondary air valves by 1/4 turn and swapped hangers from D to J.
Improved response quite a bit.

Ironhead - the California Q-Jets are not generally the optimal unit to modify, as many of them have massive airbleeds.

Reducing tension may have worked for you in this instance, but the fact that it did work may be indicative of other problems. Generally, reducing the secondary airvalve tension will create a "hesitation".

Play with this one until you receive and read Cliff's book, but I think you may wish to later do some ebay shopping for a different starting point. The Federal carburetors tend to have smaller airbleeds than their California cousins, and the mid to late 1970's Chevy cores are not that expensive.

Jon.