Thread: Gen I 350 - Performance & Gas Mileage?

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Your best mileage gain will be a overdrive trans. Also, if economy is important, dont use too big of a carb, it's just dumping unburned gas out the tailpipe. Use the carb size formula: The math formula is: CARB CFM = Cubic Inches x Max RPM's / 3456 x VE%

Max RPM's for a good street small block is probably around 6000. VE is Volumetric Efficency. A basic stock 350 is about 75% efficent while a well built small block can achieve 100%. Work it both ways and it'll give you idea of the range of sizes you're looking at. The goal is to completely burn the fuel as much as possible.

That would put me in the range of a 587 cfm (100% VE) to 783 cfm (75% VE) carb.

Was planning on going with a 600 CFM vac. secondaries.