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7 OR 8 MILES PER GALLON FROM A TBI 454...WTF!!! HELP....ANYBODY???

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Brians 60s, Jun 24, 2002.

  1. Brians 60s

    Brians 60s 1/2 ton status

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    ok, here is the scoop. I have a 1988 chevy extended cab truck. It has a 454 tbi motor that is 110% completely bone stock. I have 265/75/16 tires on it and 4.10 gears. The tranny is a turbo 400. The best mileage I have got so far is 8 miles per gallon. I get about 7.2 when I am towing. The motor seems to have decent power for what it is and runs fine, but with the milage I am getting, I think I could do better with a modified 454 and a carb. Something just ain't right here. Any ideas for me...??? Thanks in advance, Brian
     
  2. thatK30guy

    thatK30guy 1 ton status Premium Member

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    Hey Brian!!! Where ya been man?! /forums/images/icons/shocked.gif /forums/images/icons/wink.gif

    About the mpg, what did you expect from a 454?!?! I can't even do better than 5 mpg with mine!! /forums/images/icons/mad.gif /forums/images/icons/tongue.gif
     
  3. ftn96

    ftn96 1/2 ton status

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    Those tires, those gears and that NON-OD tranny are prolly the main reasons. Nobody ever said the 454 was an efficient beast. /forums/images/icons/wink.gif
     
  4. fisher1648

    fisher1648 Registered Member

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    My buddy has a 1995 (I think) crew cab and it gets 8 mpg in town and 6 pulling a big load. He's got a lead foot so I suppose tamer driving habits would likely get him nearer to 9 mpg. My old for 460 got in the 8 range as well - I figure that's normal for a big block but I'm no expert (obviously, I owned a Ford).
     
  5. JIM88K5

    JIM88K5 1/2 ton status

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    That is standard issue. Maybe a 3.73 or 3.42 ring and pinion may help. No matter what it's Rat and they are thirsty brutes. An aftermarket cam may help too...
    Jim
     
  6. NITRO

    NITRO 1/2 ton status

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    Try runnin a blown nitrous 555, then bitch about gas milage with the gas at $5.34 a gallon /forums/images/icons/tongue.gif /forums/images/icons/grin.gif

    NITRO
     
  7. thatK30guy

    thatK30guy 1 ton status Premium Member

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    That set-up would net you 15 mpg, tops! /forums/images/icons/wink.gif /forums/images/icons/grin.gif
     
  8. Eric M.

    Eric M. 1/2 ton status

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    I've got an 87 R3500, 4.56, with 235/85R/16, bone stock TBI 454, Turbo 400 and all I get is 7 MPG city or freeway.

    I've also got an 82 K3500 with a B&M Forced Induction blown 454, Holley Annular 850 carb, 4.10 gears, 36" tires, Turbo 400 and I get about 9 to 10 on the freeway (not sure about the city, probably 7). It's amazing what taller tires and higher gears will do, 'cause you know the 82 ain't usin' any less gas!

    Eric M.
     
  9. mudhog

    mudhog THEGAME Staff Member Super Moderator

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    good to see you back brian /forums/images/icons/grin.gif your o2 sencors may be bad causing it to run to rich
     
  10. BurbinOR

    BurbinOR 3/4 ton status

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    Gotta agree, it sounds about right. I've said it before, if most of the guys here REALLY knew their gas mileage, they'd mess their pants. /forums/images/icons/tongue.gif
     
  11. 70~K5

    70~K5 1/2 ton status

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    I've got a TBI 454, '95 xcab dually 454/ 4L80HD/ 3.73s/ 215/85R16s. 9mpg around town. 11.5mpg freeway trip running 70/ 80 mph. Best I ever got was from Reno to San Jose running 55 all the way got me 14.5mpg. I've got a friend with a stock '78 GMC 3/4 ton 454 t400 4x4. He gets 8mpg loaded or empty. It's a RAT and needs its GO juice. Hate to see what my freind in FLA is gonna get from his 502/502 horse in a '46 stude hot rod. /forums/images/icons/shocked.gif
     
  12. topless1tonk5

    topless1tonk5 Registered Member

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    buddy, your running 31" tires, 4:10's,a big block, and no overdrive tranny. hell, your lucky to be getting that! /forums/images/icons/grin.gif
     
  13. Brians 60s

    Brians 60s 1/2 ton status

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    Hey Wes, I have been doing the building a house thing and generaling it myself. (even though I don't know what the hell I am doing) That has been taking up almost all of my time and just plain old working. You know, slave to the grind. Good to see all the old guys are still around as well as a crapload of newbies... Anyway, I was just jealous as hell of friends claiming up to 14 miles per gallon and not less than 10. Hell If I could just get 10 that would be a 30% increase from where I am now. Sounds like a pipe dream though. I hate to think of what you are doing to get only 5. maybe I will try the o2 sensor thing. Like people are saying though, my tires and gears with the 400 are probably the reason. Good talking with everyone and hope to see more of everyone in the future..... Brian
     
  14. k20

    k20 3/4 ton status

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    We had a old 86 Dually, no OD, 4.10 gears, stock tires, 454, got 6-7 normal no AC,5-6 normal w/ AC, 5 pullin no AC, and 4 pullin w/ AC. I loved that truck, woulda been mine but my dad had to sell it one yr b4 i got my license. /forums/images/icons/frown.gif
     
  15. Donovan

    Donovan 1/2 ton status

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    I feel your pain I have a 86 crew cab dually 4x4. It has 4.56 and a 4 speed. I had the holley Proinjection MPI setup and it got worse mileage than the carb setup on there now. The carb setup has more power and is getting around .5 mile per gallon better. I plan to put a Caddy 500 in it or I will look for a Vortec 454 out of a 96 and later because they improved the cylinder heads big time.
     
  16. thatK30guy

    thatK30guy 1 ton status Premium Member

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    Brian, we are gonna be building a new house in about 2 or 3 years from now (hopefully!). We will be doing all the construction, too. /forums/images/icons/tongue.gif So I know what you mean. /forums/images/icons/wink.gif

    I got another one for you and the rest of the gang to ponder:
    A out of town friend of mine has an '84 K3500 GMC with the normal stuff...454, 400, 205, D60, 14FF, 4.10's, etc. But the kicker is, he has the Holley Projection mounted on the 454 and claims it gets 18 mpg!!! /forums/images/icons/shocked.gif /forums/images/icons/tongue.gif

    I had my doubts and still do! /forums/images/icons/mad.gif

    Anybody else care to elaborate?
     
  17. BurbinOR

    BurbinOR 3/4 ton status

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    </font><blockquote><font class="small">In reply to:</font><hr />
    claims it gets 18 mpg!!!

    I had my doubts and still do!

    Anybody else care to elaborate?

    [/ QUOTE ]

    Man, I wish we had those instant BS alert gremlins.......

    If he has been realllllyyyy fine tuning his fuel maps/spark curves and has the ability to put that thing into super lean highway cruise mode (which you can do with a TPI ECM by prom burning), which I have no idea if possible with the Projection, then he might be able to improve some...........but 18mpg? Don't think so....... /forums/images/icons/confused.gif
     
  18. Donovan

    Donovan 1/2 ton status

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    I don't think that it is possible that your friend is getting 18 mpg with his 454. Maybe 14-15 and that is it. The big block chevy head is not worth a sh*t. They are only good for racing. They have poor port velocity in the intake runners. I would love to try those vortec heads and a new cam to see if I can at lease break 10mpg. /forums/images/icons/wink.gif
     
  19. HarryH3

    HarryH3 1 ton status Author

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    BwaaHaaHaaHaaa! I'm rolling on the floor, LMAO! /forums/images/icons/wink.gif I'm not sure that a 454 could idle down the freeway and get 18 MPG. /forums/images/icons/shocked.gif I'm thinking that either his calculator is broken or his odometer is very optimistic. /forums/images/icons/cool.gif If he's got it leaned out enough to truly get that kind of mileage, it's only a matter of time until the pistons self destruct from the excessive combustion chamber temps. Especially if he does any towing! /forums/images/icons/shocked.gif

    GM, Ford and Dodge all have lots of highly paid, very educated engineers working on their engine and fuel system designs. You can bet that if any of them could figure out how to reliably get 18 MPG out of a big block, they would be shouting it from the rooftops. :sink: Heck, imagine what they could squeeze out of a 350 if they could make a 454 get that kind of mileage! /forums/images/icons/shocked.gif
     
  20. thatK30guy

    thatK30guy 1 ton status Premium Member

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    "BS alert gremlins"!!! /forums/images/icons/laugh.gif /forums/images/icons/laugh.gif /forums/images/icons/laugh.gif We have some of those in our town. /forums/images/icons/tongue.gif

    I still don't believe the "18 mpg" thing either. /forums/images/icons/tongue.gif
     

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