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Thread: how to improve fuel milage on a chevy 350 tbi? help!

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    strokin 93f250idi's Avatar
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    Default how to improve fuel milage on a chevy 350 tbi? help!


    i recently picked up a 92 gmc sierra. it has a 3" body lift and 33s. i drive it every day an im getting about 10 mpg . truck has 267k miles has a new tranny with shift kit and a new jasper rear end. im looking for some cheap fuel milage. im gonna try and do a tune up pretty soon and change the oil and fuel filter but other than that what else can i do? i need some help as this thing is killing me! thanks!
    88 f250 ext cab 7.3 c6 4x4

    87 f150 2wd 302 original aod true dual straight pipes LOUD pretty quick for stock 302

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    Full Access Member jonathan's Avatar
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    i used to have a 95 z71 and it would get 19 mpg on the highway and 13 in the city. keep it out of od under 55 that helps with city mpg. a tb spacer let me gain 2 mpg. i put a edlebrook intake on it it didnt do anything for mpg just more nuts. jet makes a chip that claims to inporve mpg. hope this helps. btw mine had 285000 miles on it they last forever lol
    1990 f250 extend cab 4x4 fuel tanks moded and a rdt group 31 bats with 4/o red cables and 2/0 black ones ip turned up 1 flat soup bowl is gone more mods to come and running on wmo96 2500 ram packing the old 8.0 chiped and spaced and geting 5 mpg in the city and 12 mpg on the highway

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    strokin 93f250idi's Avatar
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    how much does a tb spacer cost?
    88 f250 ext cab 7.3 c6 4x4

    87 f150 2wd 302 original aod true dual straight pipes LOUD pretty quick for stock 302

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    Full Access Member jonathan's Avatar
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    70 or 80 thourgh jegs or summit get the store brand one they are cheaper. i miss my old z71.
    1990 f250 extend cab 4x4 fuel tanks moded and a rdt group 31 bats with 4/o red cables and 2/0 black ones ip turned up 1 flat soup bowl is gone more mods to come and running on wmo96 2500 ram packing the old 8.0 chiped and spaced and geting 5 mpg in the city and 12 mpg on the highway

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    strokin 93f250idi's Avatar
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    well if mine doesnt pick up in milage it will be for sale . i really like the truck but i just cant afford to drive the darn thing. $4000 obo
    88 f250 ext cab 7.3 c6 4x4

    87 f150 2wd 302 original aod true dual straight pipes LOUD pretty quick for stock 302

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    Full Access Member jonathan's Avatar
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    is it 4x4 is it a extend cab how are the cab corners
    1990 f250 extend cab 4x4 fuel tanks moded and a rdt group 31 bats with 4/o red cables and 2/0 black ones ip turned up 1 flat soup bowl is gone more mods to come and running on wmo96 2500 ram packing the old 8.0 chiped and spaced and geting 5 mpg in the city and 12 mpg on the highway

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    Full Access Member jonathan's Avatar
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    you should get a dodge v10 they only get 6 mpg in the city and 11 on the highway it sucks lol
    1990 f250 extend cab 4x4 fuel tanks moded and a rdt group 31 bats with 4/o red cables and 2/0 black ones ip turned up 1 flat soup bowl is gone more mods to come and running on wmo96 2500 ram packing the old 8.0 chiped and spaced and geting 5 mpg in the city and 12 mpg on the highway

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    NRA LIFE MEMBER sle2115's Avatar
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    TBI spacer will help, also, check the snorkel. If it is the one that runs to the passenger side fender and has an "airbox" type canister on the end right next to the filter, look at Jeg's or Summit for a replacement unit. They have like a sleeve that takes the place of that can. Take the can off and look into it...looks like about a 2" hole, VERY restrictive. On my 94 I replaced it and put a spacer on it, and it made quite a bit of difference. Opens up the airflow and cools the intake charge. Not only will fuel mileage improve, but it made mine run much better. Yours may or may not have that canister, but it's worth a look and I think the kit was $15 or so.
    1987 F250 6.9 4X4 - ZF5 Trans, 3.73 Dana 60 Front/Ford 10.25 rear, Dual Rear Wheels, Carter P4594 electric fuel pump, Hydroboost, Restrictive air filter opened up, Firewall repair kit installed, new clutch, solid flywheel, m/cyl and pedal bracket, bushings etc.,7.3 fuel filter conversion, Solid state controller OEM (new controller and Motorcraft GP's), Headlights converted to relay system with 65/100 Watt Cold Ice bulbs, Class V Hitch (10,000lb WC/15,000lb WD), Air Horns, Cadet 7' X 9' flat dump bed, 5 ton grainmaster dump hoist.

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    strokin 93f250idi's Avatar
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    its a reg cab short bed. one cab corner is good and one needs replaced but the hole isnt too big. it also needs one body mount fixed, but if your interested in it i will fix the cab corner and body mount. its a pretty nice truck overall. and thanks sle2115
    88 f250 ext cab 7.3 c6 4x4

    87 f150 2wd 302 original aod true dual straight pipes LOUD pretty quick for stock 302

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    strokin 93f250idi's Avatar
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    and yes its a 4x4.
    88 f250 ext cab 7.3 c6 4x4

    87 f150 2wd 302 original aod true dual straight pipes LOUD pretty quick for stock 302

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    Full Access Member jonathan's Avatar
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    i was woundering what those go for around here.thanks now i know. just got a new idi so i dont need it
    1990 f250 extend cab 4x4 fuel tanks moded and a rdt group 31 bats with 4/o red cables and 2/0 black ones ip turned up 1 flat soup bowl is gone more mods to come and running on wmo96 2500 ram packing the old 8.0 chiped and spaced and geting 5 mpg in the city and 12 mpg on the highway

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    strokin 93f250idi's Avatar
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    Quote Originally Posted by jonathan View Post
    i was woundering what those go for around here.thanks now i know. just got a new idi so i dont need it
    i want pics! ive gotta soft spot for idi's.
    88 f250 ext cab 7.3 c6 4x4

    87 f150 2wd 302 original aod true dual straight pipes LOUD pretty quick for stock 302

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    strokin 93f250idi's Avatar
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    anyone else??
    88 f250 ext cab 7.3 c6 4x4

    87 f150 2wd 302 original aod true dual straight pipes LOUD pretty quick for stock 302

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    Full Access Member opusd2's Avatar
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    I'll toss in my 3 cents worth.

    I have an 89 GMC K1500 4x4. It has the 350 with 700R4 in it, with decent all terrain tires that offer excellent mileage, but which don't howl when I fly down the highway. No lift kit, and a fiberglass cap on the back. I can get just about 21 mpg if I watch myself and am not hauling anything too heavy. On a bad day I get 15.

    Here's what I did:

    First modification after buying the truck 17 years ago was to tighten up the front end. Remove the slop with new ball joints, tie rods/ends, new gas shocks all around with coil overs in the back. All of this reduces movement of the body and the need to correct steering, all of which requires a little more effort on the part of the engine.

    Then I milled myself a spacer for under the TBI, I used aluminum but anything that is gas resistant like plastic will work just fine. In fact, on my old 73 F100 Highboy with a 360 engine benefited with just a smaller one. But anyway, back to the GMC. I added a hotter coil, 8.5 mm plug wires and a new ESC module along with a quality cap and rotor with brass terminals ( I always went with Blue Streak Standard until the quality dropped). Then replace the spark plugs with quality ones, like AC Delco or NGK. With a hotter coil you can open the gap a little bit more.

    And after I installed a cooler T-Stat along with a Jet Thermo Power chip, I felt an increase in power, and it also helped mileage. As for the silencer tube, well, the inside can be opened up to act better but look stock. Then I went with a K&N filter for air and oil, and synthetic fluids all over the vehicle.

    I have a few more secrets that I just can't get into, but I will say that the truck will pass any emissions test as no equipment is missing.

    Good luck
    There are always greater parts to be added, bigger and tougher than what was meant to exist on that platform.
    Combine an agricultural tractor with your hard average overworked truck and you have something special.

    **W O R K - I N - P R O G R E S S**

    1986 F250 RCLB XLT Lariat 6.9l IDI 4wd C6 STOCK
    4.10 gearing with 305/70-16 tires
    F450 Hydro-Boost Brakes
    3g Alternator upgrade
    Twin commercial batteries
    Facet 12 volt fuel pump
    Flat Black Paint for the moment
    PW/PL
    Pioneer Stereo and speakers
    Synthetic fluids
    IH 1066 tractor exhaust
    Retro/Forward thinking manually switched electrical
    Case IH Primary and Final Fuel Filters




    Truck is equal part truck, equal part IH tractor/combine. It's all me though (and my little boy who helps me plan upgrades)

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