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bigger engine = better mileage?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Paxx, Jan 21, 2004.

  1. Paxx

    Paxx 1/2 ton status

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    In our trucks they start getting quite heavy quite quick with all the 1 ton crap and doublers etc. would say a 400sb get you better mileage than a 350 in a heavier rig due to the added torque or would the extra displacement call more more fuel period?

    Just wondering is all /forums/images/graemlins/thumb.gif
     
  2. tungsten

    tungsten 1/2 ton status

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    I'll be able to tell you for sure in about a month. My K5 came from the factory with a 305 in it and I'm getting ready to swap in a 350.

    My gut tells me that yes, the 350 will pull it easier thanks to the HP/TQ advantage and therefore will use less fuel in comparison.
     
  3. SUBFAN

    SUBFAN 1/2 ton status

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    Up to a point you are correct. Depending on driving style.

    400 sbc's really like their gas though....
     
  4. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    my 88 454 Sub that weighs proably 1k more then my 79 k5 gets better MPG hwy. and same normal around town driving. Noooo don't even start with the carb /FI stuff. That 79 ran perfect and passed emmision no problem so the mix was right on.

    back 15 years ago I helped a bud swap motors in a comaro. It had a stock 305 in it and it was a good low mile motor that was salvaged from a car his parents owned new and was totaled in a wreck.. We stuffed a 383 stroker in it with a little bit of a lumpy cam. Car pulled low 13's high 12's at the strip on race gas.
    It was running the same Quad the 305 had on it with a bigger set of jets. around town it got 1mpg better then the 305 and that's flogging it all the time. hwy it did even better.


    Yeah there is a point that the weight of the vehicl will overcome the engine and cause the engine to work had and use fuel.

    In the case of my Burb...385lbft of torq at 1600 RPM gets it moving quite easily. It short shifts to stay below 2500 RPM most of the time. The 79 made it's torque a LOT farther up the RPM range. normal drving It wanted to shift around 3200.
     
  5. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    [ QUOTE ]
    In our trucks they start getting quite heavy quite quick with all the 1 ton crap and doublers etc. would say a 400sb get you better mileage than a 350 in a heavier rig due to the added torque or would the extra displacement call more more fuel period?

    Just wondering is all /forums/images/graemlins/thumb.gif

    [/ QUOTE ]
    Nope... I have direct experience with those 2 motors. I wen't from a stock tired 350 to a built 400 and it likes it's gas. I used to get around 13 or 14MPG on the freeway with the 350 and a little less with the 406, then I went 3/4ton with heavy boggers, yada yada... and am down to about 10 on the freeway in OD and about 7 in town. /forums/images/graemlins/tongue.gif I like to romp on it a little though in town. /forums/images/graemlins/tongue.gif /forums/images/graemlins/grin.gif
     
  6. doctor4x4

    doctor4x4 1/2 ton status

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    a built 400 likes its gas = A Big AMEN from me
    my 77 k5 is at about 10 - mabe 12 on the freeway
     
  7. 55Willy

    55Willy 3/4 ton status

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    a 6.2 or 6.5 is bigger andyour mileage woud be better.
    all hail the DEEZEL!
     
  8. 6.2Blazer

    6.2Blazer 1/2 ton status

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    There are way too many variables involved to give a definite answer to this question...........
     
  9. 84_Chevy_K10

    84_Chevy_K10 Banned

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    [ QUOTE ]
    There are way too many variables involved to give a definite answer to this question...........

    [/ QUOTE ]

    Exactly. There is also a point where more gear will get you better MPG, but there's really no way to predict the point where it'll no longer help and start taking away mileage.

    Plus, in town, super low gears would help your MPG but that kind of gear would seriously hurt your highway mileage.

    I stopped caring about mileage a long time ago. It's been fun ever since then. /forums/images/graemlins/thumb.gif
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

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    [ QUOTE ]
    Plus, in town, super low gears would help your MPG but that kind of gear would seriously hurt your highway mileage.

    [/ QUOTE ]

    Yep. My dad put a 454 with a semi-radical cam into his truck (6000lbs) in place of a 350, which was the only change to the truck. In town MPG stayed the same, freeway dropped to 9 from 11.
     
  11. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    [ QUOTE ]
    I stopped caring about mileage a long time ago. It's been fun ever since then. /forums/images/graemlins/thumb.gif

    [/ QUOTE ]
    yep, once you lift a truck and slap on some heavy tires you might as well just forget worrying about mileage.
     
  12. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    [ QUOTE ]
    Very frequently it's more like this: bigger engine = heavier right foot

    [/ QUOTE ] Whats the purpose of building a pumped motor and not using your new found ponies?
     
  13. Beast388

    Beast388 1/2 ton status

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    [ QUOTE ]
    [ QUOTE ]
    Very frequently it's more like this: bigger engine = heavier right foot

    [/ QUOTE ] Whats the purpose of building a pumped motor and not using your new found ponies?

    [/ QUOTE ]

    Sounds like you and I have the same driving style! /forums/images/graemlins/eek.gif /forums/images/graemlins/thumb.gif /forums/images/graemlins/rotfl.gif
     
  14. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Get a diesel Max...then you can afford to eat and drive the truck daily. /forums/images/graemlins/smile.gif

    Rene
     
  15. imiceman44

    imiceman44 1 ton status

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    [ QUOTE ]
    Get a diesel Max...then you can afford to eat and drive the truck daily. /forums/images/graemlins/smile.gif

    Rene

    [/ QUOTE ]

    Amen to that

    And yes and no about the bigger is better in mileage.
    You want the engine to be confortable pulling the load, but when you get to the sweet spot, if you go bigger you will start losing mileage, and that's even without the heavy foot. /forums/images/graemlins/grin.gif
    I believe your 44 and 350 should be just about the same.
    Go with a diesel and you knock it down in Half.
    I am getting ready to swap in a 6.2 in my crew cab next week end.
    /forums/images/graemlins/thumb.gif
     
  16. Paxx

    Paxx 1/2 ton status

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    Don't worry guys I had already long ago decided that a diesel will be going in when the 350 kicks the bucket, I was just trying to stir up an interesting thread.

    I even bought a diesel parts truck b4 I bought the k5. Although if I had known I was getting a freshly rebuilt 350 in my k5 I might have held off on the parts truck though /forums/images/graemlins/thinking.gif /forums/images/graemlins/crazy.gif /forums/images/graemlins/tongue.gif
     
  17. imiceman44

    imiceman44 1 ton status

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    [ QUOTE ]
    Don't worry guys I had already long ago decided that a diesel will be going in when the 350 kicks the bucket, I was just trying to stir up an interesting thread.

    I even bought a diesel parts truck b4 I bought the k5. Although if I had known I was getting a freshly rebuilt 350 in my k5 I might have held off on the parts truck though /forums/images/graemlins/thinking.gif /forums/images/graemlins/crazy.gif /forums/images/graemlins/tongue.gif

    [/ QUOTE ]

    Right on.
    So I guess we will be seing more of you in the GM diesel Forum?
    /forums/images/graemlins/grin.gif
     
  18. Paxx

    Paxx 1/2 ton status

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    [ QUOTE ]
    Right on.
    So I guess we will be seing more of you in the GM diesel Forum?
    /forums/images/graemlins/grin.gif

    [/ QUOTE ]


    I've been known to lurk around /forums/images/graemlins/cool.gif
     

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