1bbl vs 4 bbl vs fuel
Freshman User
Joined: Dec 2006
Posts: 29
Likes: 1
I have a 300 with the offy intake, had a super comp header now crappy stock manifold, edelbrock 600 tried 500, 750, and two holley 390's. The holleys had no power and ran ok but choked the motor out.It actually ran the best with the 750 as far as all out power and highway speeds it had way more than the other carbs. I have 33" tires snow plow mount, rear locker and 3.55 gears, had 4.10's and mileage stayed the same when i swithched back to the 3.55's. I get 16-17 around town in the warm and approx the same on the highway.I have a few friends with stock EFI and they get 10-15 tops.So imagine if they had the heavier long bed like mine with the locker, plow mount, 2.5" lift, 33" tire instead of 31" ? I'm guessing 8-12mpg!!!
Postmaster
Joined: Jul 2003
Posts: 2,711
Likes: 2
From: Pittsburgh
all this being equal a 4bbl will get better economy than a 1 bbl *until* the 4bbl opens enough to outflow the 1bbl at wot.
in the midrange the smaller venturis create a stronger vacuum signal and higher air velocities which improve fuel atomization which in turn improves economy and power.
But on top a 4bbl can just plain outflow a 1bbl in the fuel department, but you get a good amount of power in return.
Yet harte3's statement is the most true of all. your driving habits dictate economy more than the method of induction ever will.
Justin
in the midrange the smaller venturis create a stronger vacuum signal and higher air velocities which improve fuel atomization which in turn improves economy and power.
But on top a 4bbl can just plain outflow a 1bbl in the fuel department, but you get a good amount of power in return.
Yet harte3's statement is the most true of all. your driving habits dictate economy more than the method of induction ever will.
Justin
Senior User
Joined: Feb 2007
Posts: 150
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i had an 89 bronco 5.0/aod, just got my 92 bronco 5.0/e4od going, but i swear up-and-down-left-and-right all day that my 83 bronco 300-6/t18 on 6in lift w/35's is sooo much better on gas yet no one believes me. every time i say that ppl argue with me all day. the old 71 f100 302/c4/4:10's was good on gas too with no help from technology. but no one wants to hear it. i hate to say this here, but 2 of my overrated, overhyped, overmagazined 80's c**v 305 carbed (305 carb about the best part of'm) where better on gas too. i know efi has tons of advantages but sure not mpg. i guess the old carbs don't give the automakers the power to program them to chevron's specs. allright everyone get angry-let's hear it.
Senior User
Joined: Aug 2007
Posts: 156
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From: Greensburg,PA
devja71 I agree with you for the most part. A properly tuned Carb will get good fuel economy with the right driver habits and gear/tranny/tire set up. However in some vehicles the FI setup is better. I like to stick with carbs because they are easier to work with and I like older trucks anyway.
Senior User
Joined: Jul 2006
Posts: 242
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I've got the Carter YF 1bbl on my '76, all stock intake and exhaust. The truck's a long bed Supercab 2wd, with a 3.00 rear end - and I've also converted it to manual steering. I get 15 in town and close to 20 on the highway. The truck doesn't have much acceleration, but lots of grunt, and a wide power band.
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