Quote:
Originally Posted by northboundtrain
I didn't mention that one of the reasons I'm thinking of the Performer carb is that I have a buddy who is very experienced with them and can help me tune it. It's what he recommends in lieu of the Q-jet.
The Performer 1406 is a 600 cfm carb factory tuned for fuel economy (as opposed to the 1405 which is the same carb but tuned for performance).
There's also the 500 cfm 1403/1404 which are intended for 305 cu. in. and smaller engines. They are calibrated for performance, so I might need to replace jets and rods to tune for economy. By my own calculations, I would have to be running at more than 5,000 rpm before running out of air with a 500 cfm carb, but I suppose it might not be any more efficient if the secondaries are opening sooner than on a larger carb.
I've thought about 2-barrel carbs too, but I need to understand the theory behind why 2-barrel would be more efficient. At part throttle, isn't a 4-barrel effectively a 2-barrel with even smaller barrels? Would a 2-barrel be more efficient at WOT, but not necessarily otherwise?
I also want the ability to tow with this truck, so there may be times when I need four barrels.
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Stick with 4 barrel carb , the venturi will be smaller in general and that helps with tunning an low speeds .
While I have worked on those and there very tuneable I am not sure for eco purposes but probably can help .
I had but a 450 cfm 4 barrel on a old 75 buick 350 ci , this did give better mpg a bit and improved low-mid range response . for eco driving you don't need hi cfm at all . though depending on gearing of your truck you might need 600 if revs are a lot higher than a car .