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  1. #1
    Jr. Engineer Falcone's Avatar
    Join Date
    Apr 2009
    Toronto, Canada

    Default What type of milage could I expect from this engine/trans combo?

    350 chevy small block motor with Aluminium Vortek Intake, Vortek Heads, Edelbrock Performer RPM Intake, Gear Drive, Mini Starter, Crane Cam, Flowtech Headers, Aluminium 4 Core Griffith Rad, 350 Turbo Tranny with 2400 stall converter, 10 bolt posi-rear end with 411 gear ratio.

    Any ideas.. trying to figure out if I could use it was my DD'er as well as toy. Mostly highway driving to work, but usually gridlock for 25 min out of the almost hour drive home, only 20 min usually in the morning due to it being 5am.
    2010 Sierra Nevada Edition
    4.8L Ext. cab - Black Z85 4x4 G80
    Shaved a couple badges and 4x4 stickers, DeeZee Red label Low Pro gloss black Brite plate cross box,DeeZee gloss black Brite plate bed rail caps , K&N,more to come.

  2. #2


    What size tires and how much of a lead foot do you have?
    With the right gearing, size tires, and driver you could concievably get into the high teens.
    Swap that turbo 350 for a 700R4 and you could probably add a few more MPG's.

  3. #3


    8 to 10. The 3 speed trans and 4.10 will kill you. BUT IT WILL BE FUN! I have the same thing in a car and I don't bother to calculate my milage cause it sux. I actually get better gas milage TOWING the thing with a 4.10 in my truck (12 - 14 MPG). This is due to the fuel injection (precise fuel metering) and 30" tires. The car has a carb and 26 or 28" tires, depending on how it's set up at the time.

    I guess tire size (diameter) would be important to help calculate MPG, cause the RPM you'll be turning dictates that. My truck turns 3000 RPM, when towing, my car turns 3500 at 65 - 70mph and is wound up like a swiss watch.

  4. #4
    murdog94's Avatar
    Join Date
    Feb 2008
    Cloquet, Minnesota, United States
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    I agree with the 700R4, built up it will take a lot of abuse and will net you mid teens with the 4.10s out back. Ive seen a lot of people run that set up, with an OD tranny and it helps a lot. But it will still be a gas hog if you run it to hard.


    1997 Chevy S-10 Blazer 4X4 with 330K miles and counting (Hunting rig).

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  5. #5

    Join Date
    Jun 2006
    River Ridge Louisiana-4 miles W of New Orleans-didn't flood-water stopped 800 yards away.


    Wow, it is really hard to approach what factory setups can get with EFI and electronically controlled trans with lockup in top gear.
    I'm guessing your trip is maybe 15 miles?
    It takes 1 hour to get home-lots of gridlock?
    This setup will probably suck in .8 gal/hr or more just idling.
    You will be lucky to average 10 mpg since you are in gridlock so long.
    Now you might get high teens-like TBPLUS10 said- while tooling along at 55-60 mph-hy driving- but the rest of the time you will be under 10 mpg.

    Modern factory setups are just sooooo good. The stock 5.3 are over 300 hp and get over 20 mpg hy with their EFI,O2 sensors, air mass sensors,ECU, fancy smart transmissions.
    If gasoline spikes to $4 you might be sucking 4 gallons a day-$15 or more a day.
    If mpg is a concern try to adapt a stock 5.7 or GM performance drop in motor that uses a modern FI setup and trans.You would need a trans and entire wiring harness and FI setup, but there are lots of salvage yards for that. The drop in 383 vortec stroker would be tempting.
    1998 suburban-
    1/2 ton

    199500 miles

  6. #6


    Hi phoebeisis. I love to see that Modern factory setups. Can you post some photos of it? I really love to see it. :D

  7. #7

    Join Date
    Jun 2006
    River Ridge Louisiana-4 miles W of New Orleans-didn't flood-water stopped 800 yards away.


    Trophyyride- I was unclear.
    I mean literally a factory setup-say a factory 5.3 making 320 hp will EPA 14/20. A 6.0 or 6.2 will make almost 400 hp.
    I would literally try to adapt a factory setup if iI was concerned with mpg. Nothing with a carb will approach what a modern factory EFI with modern controls will get.

    His 1992 might not be too tough to adapt a 5.7 with EFI-maybe the throttle body which will give better FE than a carb. Carbs are poison for FE. I would see if a Vortec 5.7 with its trans/wiring harness and fancier fuel injection with ECU could be installed. It would get 23 mpg hy easily with that little truck, but would make 250 hp-about double what his 4 cyl makes.

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