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mpg questions

Discussion in 'The Garage' started by duanel, Apr 17, 2006.

  1. duanel

    duanel Registered Member

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    Okay I have a 73 k5 with 350-350-203 stock q-jet and gm hei I get like 8-10 mpg. what kind of gains could I get with a part time kit (and is it worth it. I like all whell drive) and how much of a gain could a tbi fi conversion get me (not that I really want a computer and all the extra sensors that it would require. I understand and like carbs) or do I just live with the mielage and enjoy driving the rig or start driving the s15 more (underpowered p.o.s.)
     
  2. yoshisv

    yoshisv 1/2 ton status

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    My k5 gets around 15 mpg with a mildly built tbi 350.
     
  3. steve_kibbe

    steve_kibbe 1/2 ton status

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    I you want to get an idea, remove your front drive shaft.
     
  4. Wishbone

    Wishbone 1/2 ton status

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    My '84 with 350 and edlebrock carb is only getting 7-8 mpg. Tbi's are not cheap and would take a lot of mileage to make up the difference.
     
  5. duanel

    duanel Registered Member

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    Thanks for the replies (especially wishbone) I do not drive enough to justify the tbi swap, but I really do not want to remove the front d-shaft (though it is a good idea) just to see how little it helps with mpg ( I doubt it could be over 2-3, which I would consider not worth it) so I guess If I want 15+mpg I will just drive the mini jimmy.
     
  6. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    11-13 mpg is about right for your truck, anything much less than that you should be able to do some tuning. I had a 77 Blazer with the same combo, 350 w/ Q-jet, TH350, 203, and 3.08's and 31" mud terrains. It got a pretty consistant 11 in town and 13 on the highway. It did have the part time kit though...

    2-3 mpg may not sound like it's worth it...but that is 20-30% which is huge.

    Rene
     
  7. blazinzuk

    blazinzuk Buzzbox voodoo Premium Member GMOTM Winner

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    Thats what I got with my 73(350-350-203 with quad) before part time 8-10 mpg after the part time kit 10 all the time no matter what. So I would say expect 1-2 extra mpg. I think you would get more benefit from having someone who knows quads tune the carb. My bro in laws blazer (350-350-203) would get almost 14 on the highway after he tuned it up and got the carb worked on. His t-case broke and he put a full time one in and it went to 11. Converted back to part time and right back up to 14.
     
  8. steve_kibbe

    steve_kibbe 1/2 ton status

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    You could just swap in a 6.2, and get 17+:D
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

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    Always worthwhile to ask, are you sure you can trust the speedometer? If you can't, that will skew your mileage. Just something to check, if you haven't already.

    And as an edit, Rene is dead on. You won't see a 20% improvement in mileage, same driving habits, any other (non-extreme) way unless you convert to a diesel. 20% increase in mileage is HUGE.
     
    Last edited: Apr 18, 2006
  10. 70jimmy

    70jimmy 3/4 ton status Premium Member GMOTM Winner

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    I had a 74 with 350 350 203 full time and I did the part time swap. I saw 3 mpg. It was my daily driver and I commuted 30 miles to work each way. Even though the mileage may not seem like a big deal it adds up especially with gas prices where they are.

    I also liked the reduced wear on the front end components. It made turning better too.

    tuning helps, HEI, properly adjusted carb, and so on and so on. I ended up selling because of the mileage when my commute jumped to 50 miles each way.
     
  11. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Well, i have an 89 blazer with a 350/700R4/241 running 35's and 4.56's and i'm lucky to get 9mpg around town on average, my rig has 228K on it so the engine is tired and i'm assuming that does contribute to the mileage being low like it is. Before anybody ask, i did have my speedo recalibrated after my tire/gear swap so it is correct.
     
  12. thfonz98

    thfonz98 1/2 ton status

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    with a 50/50 highway/city driving schedule with my 91 k5 350tbi/700r4/241 with 3.73 10bolts on 31" a/ts with everything stock(174kmiles) i can get ~15.8mpg driving like an old man or just over 14driving like i want:D
     

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