Ls fuel economy

Discussion in 'LSX + Carb Swaps' started by Pip7899, Jan 1, 2017.

  1. Pip7899

    Pip7899 Newbie

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    New member first post. I am looking at a new engine. LS swap is a very simple swap for me to do. My concerns is fuel economy. Most guys don't care but my commute is roughly 100 miles a day. What numbers are you getting at the pumps? I'd really like to run a 4.8 w the 4l60 for the cheapest scenario.
    So 4.3 vs 4.8......
    Truck is a 96 RCSB w a siezed 4.3
    Pockets aren't deep. Was also considering a 4.3 mated w a 6L80E hell even a 6L90E and put together a stand alone for that. But it would be one or the other couldn't afford both. Any input? Or any idea on mpg City/Hwy.
     
  2. Black_cirrus

    Black_cirrus I'm Awesome

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    The 6l80&90 both need a 58x crank signal so you'd have to get the matching 4.3 parts which might be easier found as matched take out and at that point which ever set up you get a better deal on but I'd guess the extra parts on either swap would buy a ton of extra gas, Over a simple 4.3 replacement. And service costs on the current trans would be way less.
     
    Last edited: Jan 1, 2017
  3. Pip7899

    Pip7899 Newbie

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    Huh. I had no idea on the 58x signal. I'd have to log into gm and read up. I could look into a manual valve body for a 4.3/6l80 but idk if there are even any made lol
    I'd have to find a steal to come up w a ls plus a 6l80! Or get a second job lol
     
  4. Black_cirrus

    Black_cirrus I'm Awesome

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    I've never heard of a manual vb but that's an interesting idea, it's full computer controlled and the TCM is in the pan if I understand right.. a 4.3 manual trans probably a nv3500 would be the best mpg vs dollars in my head. But I have an almost 8 mpg 454 so I may be a bad judge.
     
  5. vic_v8

    vic_v8 OBS Enthusiast

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    I have a 1988 (square body) V2500 Suburban. Its got 60/14 swap, and a built TH400. 4.10 gearing and 35" tall tires. I get 14-15 mpg with it. If it had OD I'd probably get 16-17.
     
  6. Pip7899

    Pip7899 Newbie

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    I'm looking for the combo closest to 25mpg. Lol who has built the unicorn!?
     
  7. Thatfordguy

    Thatfordguy Because I can!!

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    Our 04 rcsb with a 4.3 only gets like 20:(
     
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  8. vic_v8

    vic_v8 OBS Enthusiast

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    A RCSB lowered, with a 4.8/T-56 could probably hit 25.
     
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  9. Pip7899

    Pip7899 Newbie

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    It is lowered. Not sure how a t56 would fit but that's an option
     
  10. Pip7899

    Pip7899 Newbie

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    I was even considering a 4.8 w AFM and DOD but that's a more expensive swap
     

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