hello, i recently purchased a 1957 F600 with 14ft. flat bed. it has either a 390 or 391 V-8 and has HOLLEY 4bbl. carb and 4 bbl. intake on it. i would like to put a 2bbl. carb and 2bbl. intake on it. what would this cost. also how much would this increase or decrease my fuel mileage. hopefully it will be better that the 4 to 5 mi./gal. i am getting now. and would rebuilding the crb i have now and tuning up the motor increase my mileage any? thanks, 57_F600

 

I would definately try the tune up first. Pay attention to the plug wires and timing. Set the timing as far advanced as you can get it for the best mileage. Keep advancing the timing until you hear just a little bit of a knock on acceleration or load, then back off that setting by 1-2 degrees. For additional mileage increases, side gap your plugs...you'll have to purchase plugs more often, but you can expect a 10-15% increase in mileage, get a K&N air filter...nothing flows better than a K&N, and instead of investing in a 2 bbl and intake, put on some full length tri-y headers and 2 1/4" exhaust pipe through a set of good Flowmaster mufflers. Then start thinking about leaving your tailgate down to decrease wind drag and dropping any additional weight that you are unnecessarily carring around. Keep your tires inflated to the top side of the limits and don't run oversized tires. If you have an automatic, consider swapping it for some type of overdrive tranny or change your rear end gear to a 2.73 or so. Your rear gear will gain you great mileage by keeping your operating rpms low.

Now, switching to a 2 bbl may not buy you any mileage depending on your driving habits. If you've always got your pedal to the metal, then you will see an increase...but consider that the front barrels and venturi, etc. on a 2 bbl are normally larger than the front barrels of a 4 bbl carb..so if you drive conservatively, you're probably better off with the 4 bbl carb.

Slik