Thread: lowrise dual quad 350 sbc horsepower???

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I tend to go with four webers on this one except for the carb size. Several years ago I was running a 350 with a mild cam, headers and four speed in a 65 Chevy Biscayne. I started off with a single 625 AFB and eventually went to a pair of 625s on an Offy dual quad intake. It ran great, and I only dropped about 1 MPG.

The 600 CFM carbs should do fine once their dialed in and here's why.

PROPERLY set up the linkage should be progressive. This means that during the majority of driving situations he'll only be running on the front 2 barrels of the rear carb. When He kicks it the front 2 barrels of the front carb will open. The rear barrels on both carb open "on demand". There is a butterfly valve over the rear throttle plates on the AFB style carbs that is counter-weighted to remain closed until enough vacume is under it to pull them open (and then only as much as the engine will take. Chances are that the secondary air valves will open very little if at all.

Chances are that going to 500 CFM carbs will not run as well as 600's as the 2 barrels that he will be running on the majority of the time will be too small.

The one suggestion I would make would be to only run the choke on the rear carb. Even though it does idle on both carbs the only one that is critical to have a on choke is the primary one.