Gas mileage question..

[77k10]

I drive a 77 k10 4x4 with a 400 small block. Lifted with 33's. Im getting 6-7mpg, does this seem right?? I know its a lifted oldie and i really don't give a hoot.. any tips besides nut up and shut up?

[cmarentes]

Wow! you get better gas mileage then i do lol. Any issues while driving or idle?

[1998454]

I would think it would do a little better than that unless the 400 has a huge cam in it.

[Snowboi]

Seems right, what gears? Driving habbits (flooring it, hard take offs, slow take offs, etc.)?

[vic_V8]

hmm, my old set up netted me 15mpg (corrected), but I had OD

350 4 bolt main (300 hp), 700R4, 3.42s (I never checked, might have been 3.73s), and 35s.

My buddy has a tired 350, SM465, unknown gears in 1/2 axles, and gets 15 mpg corrected with 32s

[Your41Plague12]

I get 6-7 around town in mine too. On a truck with the aerodynamics of a brick that's been lifted, I don't find it all that surprising.

[84_K10Guy]

Hm... sounds about right. I'd be able to get a better estimate if you were to tell us what your driving style is, but if you drive like I do then that's about right. 400s can get pretty thirsty.

[jimbonice]

Send a bit low to me. My dually crew cab, 454 with 32's gets 10. Is running rich?

[77k10]

Sorry for the really late post, lol forgot all about it. I drive moderate, never really floor it. I pet the gas pedal now since gas prices are so high. Im not sure if im running rich? stock gears.

[rocking chevy]

sounds low to me. my suburban with a worn out 350, a worn out 3speed transmission(so no overdrive), 8 inch lift, 35s, and 4.10s gets 12-13 mpg.
its an 89 so its tbi fuel injected. I don't think that would make a difference though.

[1988 GMC 355]

sounds low to me. my suburban with a worn out 350, a worn out 3speed transmission(so no overdrive), 8 inch lift, 35s, and 4.10s gets 12-13 mpg.
its an 89 so its tbi fuel injected. I don't think that would make a difference though.

Totally different injection system, makes a huge difference and you are comparing apples to oranges.

[rocking chevy]

oh I'm so sorry. its not that different. and i guess if I'm getting better mileage because i have a better injection system, then if the op gets a new carb so his is better then he should get about 12-13. according to you...right?

[1988 GMC 355]

oh I'm so sorry. its not that different. and i guess if I'm getting better mileage because i have a better injection system, then if the op gets a new carb so his is better then he should get about 12-13. according to you...right?

If his carb is worn out or not tuned/jetted right then yes it would make a huge difference, plus you have a 350 and he has a 400, alot different. The TBI injection system is better than a carb.

[rocking chevy]

If his carb is worn out or not tuned/jetted right then yes it would make a huge difference, plus you have a 350 and he has a 400, alot different. The TBI injection system is better than a carb.

I was just saying what mine got. you didn't criticize the other person above that said something about a 350, so why did you do it to me? Its like you went out of your way to say a dumb comment on someone else's thread instead trying to help him.

[1988 GMC 355]

I was just saying what mine got. you didn't criticize the other person above that said something about a 350, so why did you do it to me? Its like you went out of your way to say a dumb comment on someone else's thread instead trying to help him.

It was not a dumb comment I made at all and I am trying to help, don't get all pissy and defensive because I was trying to not let the OP think he should be getting MPG on par with a totally different injection system. Yes, others said what they got with their 454's and 400's and 350's in their carb'd trucks, not TBI burbs

[rocking chevy]

It was not a dumb comment I made at all and I am trying to help, don't get all pissy and defensive because I was trying to not let the OP think he should be getting MPG on par with a totally different injection system. Yes, others said what they got with their 454's and 400's and 350's in their carb'd trucks, not TBI burbs

Im not getting defensive, and I wasn't trying to mislead the OP either. I was just saying what I got, just like the other people with different engines did. I didn't see the problem saying what I got on an engine not that deferent from his. the main thing different is mine has tbi injection, and tbi isn't that much better that a plain old carburetor.
I could also say Im getting 11mpg with my 97 gmc 350 vortec, and I could say its because of the sh!tty vortec fuel injection, but its because it has misfires and bad intake gaskets.

[Quyonmob]

oh I'm so sorry. its not that different.

TBI and carb are VERY different, if you don't think so, I don't know if I can take you or your advice seriously. :smh:



OP, Start with an ignition tune-up/check, timing.

Dig into the carb after that, likely time for some tinkering. I would expect 10+mpg from your truck.

[rich weyand]

What carb is on it?

[dalaigh]

What trans and transfer case do you have? And is the engine stock or does it have some speed parts?

And I'd do what Quyonmob said and service the ignition system first, then if the carb is old rebuild it. If it's the factory quadrajet rebuild it, don't replace it with an aftermarket. The quadrajets are good carbs, and will be better then edelbrock or holley carbs when it comes to fuel economy.

[planb4x4]

Well i just read this and i felt as if that was kinda low, I'm getting like 14 highway and about 8-10 city with my k10.... i have a 396bbc 6inch lift 35's and 411's, i do have an overdrive trans but i very rarely ever get it into OD while driving around town.
That being said i would start with carb adjustment and see if that helps, then maybe plugs, wires, cap and rotor if that hasn't been done in a while... and if that doesn't do anything i might rebuild the carb for sh!t$ and giggles.

And also what Dalaih said quadrajet's are great carbs when dialed in, thats whats on mine and it preforms well with fuel economy and or beating on it.

[Your41Plague12]

I have a 4.10 gears, 38x15.50's, a TH400, a 350 (hopped up a little, 350 HP), and a factory Quadrajet with electric choke. The carb is freshly re-built and jetted properly for my application. The guy who re-did it has been doing it for upwards of 30 years. All of these nice parts, and my city MPG is 6.28! Old trucks are old trucks, they only do so well on fuel.

[rich weyand]

Your41Plague12
Re: Gas mileage question..

I have a 4.10 gears, 38x15.50's, a TH400, a 350 (hopped up a little, 350 HP), and a factory Quadrajet with electric choke. The carb is freshly re-built and jetted properly for my application. The guy who re-did it has been doing it for upwards of 30 years. All of these nice parts, and my city MPG is 6.28! Old trucks are old trucks, they only do so well on fuel.

You should be getting more like 10. My dad had a 75 F-250 with a 462 cid Lincoln engine, C-6 four-bander and trailer-towing ratio, and he got 10 mpg all day long with it.

You might want to get a air/fuel ratio meter and see what kind of mixture you're running. I got this one and am very happy with it.
http://www.amazon.com/NGK-Powerdex-Air-Fuel-Ratio-Monitor/dp/B0018MUNTM/ref=sr_1_sc_1?ie=UTF8&qid=1332431975&sr=8-1-spell