How can i improve a lil bit on gas mileage

[87 V20 Scottsdale]

Is your truck 2 or 4 wheel drive? My 383 has been getting 10-12 mpg, depending on how it's driven.

[383Chevy]

Originally Posted by cableguy0

You killed your mileage in the process of trying to find more. Switching to a 2bbl will almost always hurt gas mileage. Going to taller tires with a higher gear has you somewhere around the equivelant of a 2.73 gear. Your lugging your engine by having the rpms so low during cruise. Go back to the 4bbl and put some more gear in it. MId 2k rpms is where a small block likes to be. Lower rpms is not always better. If you were getting 14mpg with a 383 in a heavy truck you should have left it exactly how it was because that it real good mileage for one of these old pigs with the aerodynamics of a brick.

Prolly gonna hook the 4 back up tomorrow and find me some 3.73's

[383Chevy]

Originally Posted by 87 V20 Scottsdale

Is your truck 2 or 4 wheel drive? My 383 has been getting 10-12 mpg, depending on how it's driven.

2 wheel

[mongoose]

'screaming' or not... fuel efficiency is about volumetric efficiency.. where your rpm's land is where they land 'screaming' is usually better than lugging around...

[zackary027]

i had a 83 swb with a hot sb 400 most the parst came out of my dads super street race car it had a high gear and 700r4 with a 4bbl holly 600+- and was able to get 15 must have just been that right combo of course when i got into it it would kill a tank in a hurry

[383Chevy]

Well imma just hook the 4brl up gets 3.73's gears and still check for leaks just incase i appreciate it guys

[mooseknuckles]

so you have a 2bbl 383, with a th350, 2wd with 33" tires and 3:23 rear gears? first put the 4bbl back on and give it a tune up, plugs, wires k&n filter, timing set prop. then change the tires to something normal say around 28". even 31's would be better than the 33"s. that should help some, then look for a 700r4.

[pig rig]

Originally Posted by 383Chevy

So im an oxymoron? figured id post here so i wouldnt get bashed but its starting to look like it thanks for the help NOT i guess i wont post here anymore

no your statement was an oxymoron after reading all the post AFTER my post you give possible reasons why your truck is getting bad gas milage but prier to my statement all you said is you have a built motor and you dont understand why its not getting the same milage as a car that 2/3 the weight and one of the most aerodynamic vehicles gm ever built

and now with that said you pointed out one thing that needs to be fixed first. you said the filler tube hose has a crack in it
your sucking air in to the tank and you have an open system that works best closed with negetive pressure. its just like leaving the gas cap off
whats happening is your pump can suck MORE FUEL easier because it dosnt have the back pressure and by not having the back pressure it also creates a syphon

[N2TRUX]

Originally Posted by 383Chevy

So im an oxymoron? ....

Just so you know...An oxymoron is a figure of speech that combines contradictory terms. Oxymorons appear in a variety of contexts, including inadvertent errors such as extremely average

[383Chevy]

Originally Posted by pig rig

and now with that said you pointed out one thing that needs to be fixed first. you said the filler tube hose has a crack in it
your sucking air in to the tank and you have an open system that works best closed with negetive pressure. its just like leaving the gas cap off
whats happening is your pump can suck MORE FUEL easier because it dosnt have the back pressure and by not having the back pressure it also creates a syphon

Right that will be fixed soon i dont have the money at the moment like i said i got it all figured out now because you guys helped thanks

[blackbeaSSt]

all you guys with 383's+ are making me feel bad about my 305 with a mild cam getting 9mpg