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Gas Mileage question

Discussion in 'The Garage' started by k5 krawler 50, Jan 18, 2005.

  1. k5 krawler 50

    k5 krawler 50 1/2 ton status

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    Just wondering what i can do to get better gas mileage. Right now i am probably about 10mpg, maybe a little less. I have a sbc 400, 3.42 gears, and really need some help on improving the gas mileage, i already have dynomax dual exhaust, so i dont think any new muffler system is going to help. I was checking into those tornado things that go inside the air cleaner, but i dont really know if that would be a waste of money or not. Any help is greatly appreciated. Thanks.
    Cory
     
  2. kgblazerfive

    kgblazerfive keymaster Premium Member GMOTM Winner

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    Buy my 91 Honda civic it gets 33 or so mpg:D
     
  3. Sidepipes

    Sidepipes 1/2 ton status

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    I get 11 in the winter and up to 14 in the summer with a stock TBI350/700 and 3.42 gears and 33's.

    I'd say you are doing fairly well since you have 56 cubes on me and a carb instead of tbi
     
  4. 87BrnRsd

    87BrnRsd 1/2 ton status

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    How about doing a tune-up? Some new plugs, wires, rotor, cap, air filter, fuel filter, some carb cleaner. That should help some. It will also help a lot if you can manage to keep your foot out of it. It is hard to do though.

    BTW- Dont buy a tornado. They are a big waste of money.
    -Harrison
     
  5. AkMudr

    AkMudr 1/2 ton status

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    10 really isnt THAT bad..'84 3/4ton 122k, 350/400/208 on 35's, 4.10 gears and I'll get MAYBE 11 mpg goin downhill with the wind on my back, but then again, I already knew what kidna mileage I was gonna get before I gto a truck like it. lol. Maybe a edelbrock FI kit next year.

    But like some have already said, a good tune up should help out alot. Check yer timing as well. Consider changing the fluids in yer axles, tcase and tranny..believe it or not that does help out, even if it is to a minute degree.
     
  6. k5 krawler 50

    k5 krawler 50 1/2 ton status

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    I am thinking about getting new plugs when i do my oil change this weekend, but its a pretty new motor, probably likw 5000 miles on it, i have taylor 8.5 wires, i have an after market air filter. Yea keeping the foot out is pretty hard to do, and i havent actually punched it in a long time, i only go like 55 max any where, and i drive like a grandma, which mite be hard to beleive since i am only 17. Any way thanks for the help.
    cory
     
  7. AkMudr

    AkMudr 1/2 ton status

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    If yer only gettin 10mpg on a motor with 5k miles, only 2 things really come to mind...a carb out of tune or a heavy foot.
     
  8. k5 krawler 50

    k5 krawler 50 1/2 ton status

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    i was just talking with my dad, and he said that we need to re-jet it, so maybe that will help, also i think its running a little rich, so we are going to udjust that also, and make sure there is no lose bolt around the manifold, or the carb, so hopefully that will help. thanks for the help
     
  9. AkMudr

    AkMudr 1/2 ton status

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    Sounds like a plan! What kind of carb are you running?
     
  10. divorced

    divorced 3/4 ton status

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    I've only been thinking of two things lately and one of them is fuel injection. I plan to make everything I own have fuel injection. Maybe it would help with your mpg?
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    How much is city driving? Any one of these trucks (gas) has a hard time getting much over 10MPG in the city, even stripped down/as light as possible with a 350.

    If it's all freeway, check your distributor, make sure your advance mechanisms are working right, thats a common problem on older distributors. Check the cap and rotor to make sure the contacts aren't all corroded/loose either.
     
  12. k5 krawler 50

    k5 krawler 50 1/2 ton status

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    i am running an edelbrock performer 750 cfm with manual choke. i was thinking about fuel injection, but i dont have enough money for that, i have to save for college. I will talk with my dad about the distributer, but i mainly do city driving with an average mph around 45 and one stop light. Also when i do hit the free way its only for a couple of miles and thats about 55-60 for me, any thing higher then that i can watch the fuel gauge start to point and the mph gauge.
     
  13. k5 krawler 50

    k5 krawler 50 1/2 ton status

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    I just checked with my dad about the advanced mechanisms in the distributor and he said that after breakin we checked them so they should be fine, also about the corroded ends, the distributor is pretty new, so i dont think that is a problem, but i will check it. thanks.
     
  14. ssls6

    ssls6 Registered Member

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    First off a 750 is too big for your engine. I would really be suprised if you turned enough rpms to need a 750. A 650 would be much better. Second, a 700R4 instead of the T350 will make a big difference if you do many highway miles.
     
  15. k5 krawler 50

    k5 krawler 50 1/2 ton status

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    ok cool i will have to check in to all that, thanks for the help.
     
  16. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    i got 14 before the lift and tires
    after the lift and 35s i got 10-11 with a speedo thats off.
    stock 350 w/headers 700r4 and 3.42s
    with the new motor i hope to get 8 :cool1: but i have no clue what im gonna get
     
  17. Bhintz

    Bhintz 1/2 ton status

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    A SMALLER CARB 600cfm
     
  18. diesel4me

    diesel4me 1 ton status Premium Member

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    my 400 likes to drink too---

    The 400 SB in my 74 K20 got 8-11mpg with the q-jet carb that came factory on it--I put a 625 CFM Carter AFB 4 barrel on it,and it now gets 11-14 mpg,not much difference,but I noticed much better acceleration and slightly more power with the Carter carb--but I also noticed the Carter doesnt like it when you climb up a hill or snowbank,or get the truck tilted to one side,it tends to flood and stall the motor,where the Q-jet would keep running until you nearly rolled it!....

    I dont think your 10 mpg is all that outrageous,considering theese trucks weigh 5000+ pounds and big tires and high gears hurt mileage too,if you have them,any city driven V8 is unlikely to deliver much more than that,even if its tuned perfectly,especially in the colder weather--the cold will cut mileage up to 50 percent in many cases,when the choke stays on longer....only one real way to get good mileage with a fullsize GM truck--get a diesel,or stay home more..:crazy:
     
  19. 74Chev

    74Chev 1/2 ton status

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    The scary part is that my wife's 2003 Hemi powered Dodge Ram only gets 9-10 city 14.5 on the highway, so I don't feel too bad about getting 11 with my 400 and 35" swampers. I guess the engineers haven't learned much in 30 years.

    In my shop most of the fullsize SUV and fullsize pickup drivers say they average about 9-13 MPG in combined city/highway. The biggest improvement in mileage that I have seen is using the name brand fuel. It DOES make a difference. Some customers claim their import 4 cyls. get about 40 more miles out of a tank than with brand X.
     
  20. k5 krawler 50

    k5 krawler 50 1/2 ton status

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    thanks for the help, like most of you said 10-14 is pretty standard for our types of engines and what not, and if i wanted really good gas mileage i would have built a 4 banger for the blazer, I was thinking about re gearing do you think that would help, i am running a 33" ssr, which is bigger then my friend's 35, and i was wondering if that would help. Also does the edelbrock q-jet come in 600-650 cfm? Thanks
     

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