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Thread: 4bt cummins

  1. #1
    Senior member spectreblazer's Avatar
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    4bt cummins

    i've been thinking for awhile now about swapping the old 350 for a diesel. my goal is to improve the fuel economy (anything is better than 6mpg) and have some torque for pulling.

    current setup: 8" lift all suspension, 35" tires, 4:10. stock 10 bolts front and rear.

    from what i understand the 4bt will work in these k5s with some modifications. the ones i have seen are almost all manuals. from what i also understand the automatics are not enough to handle the torque.

    what would be the best way to go about this? as far as a donor vehicle? what tranny and transfer case would hook up to the 4bt. i currently have the turbo 350 and the 203. i believe adaptors are pricey and having a manual would be kinda cool. i've also heard of 20+ mpg.

    can anyone offer incite?


    2000 Saturn Sl1-daily driver

    1997 Ford F250 7.3L diesel

    1982 K-5 350 w/turbo 350/203-Play truck

    1984 K20 w/1 ton dually rear 6.2L turbo diesel w/700r4/208-Work truck/daily driver-coming soon

    1991 C10 suburban soon to be k10

    "Before you criticize a man, walk a mile in his shoes. That way, if he gets angry, he's a mile away and barefoot."

  2. #2
    Unofficial Diesel Guru Senior member Koots's Avatar
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    4BT Swap Forum

    I can't be much help to you, other than i know that 4BT's are commonly found in bread/postal vans and most all chevy transmissions can be swapped to them with ease. I know that most bread vans came with SM465's or TH400's IIRC when mated up to the 4BT's.

    Otherwise i suggest grabbing a 6.2L, grabbing a 4911 injection pump and 6.5L turbo setup. That can net you near stock 6BT power (that's about the most your gonna get out of the engine before serious mods though), low engine weight (800lbs or so), relatively easy to find and cheap parts, etc. Not as much of a performer though.
    1983 GMC Jimmy

  3. #3
    The man, the myth, the legend adam89k5's Avatar
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    i dunno bout a 4bt but i know a 6bt will hook up to the np241 and has an auto tranny that can handle said torque. its what i was thinkin bout doin.

    Its a rock, GET OVER IT!

  4. #4
    Senior member spectreblazer's Avatar
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    yeah, the only concern i have with the 6bt is the weight. i've seen a few guys that cut the frames and re-weld and plate a new 1 ton frame in the front. way to much work for what i want. a 6bt is interesting and if you got the time go for it. mine is gonna be a winter project if i can even find a 4bt. i've only seen 2 in the entire state.

    maybe i'll take a look at junkyards. i really don't want to re-build one but if i could get one cheaper.


    2000 Saturn Sl1-daily driver

    1997 Ford F250 7.3L diesel

    1982 K-5 350 w/turbo 350/203-Play truck

    1984 K20 w/1 ton dually rear 6.2L turbo diesel w/700r4/208-Work truck/daily driver-coming soon

    1991 C10 suburban soon to be k10

    "Before you criticize a man, walk a mile in his shoes. That way, if he gets angry, he's a mile away and barefoot."

  5. #5
    If your only getting 6mpg, there is something wrong with your blazer or you drive like an asshole. If you are not short on cash, go for the 4bt. If you don't have a money tree look into a 6.2. Like Koots said, most of the frito lay vans run the 4bt w/ a th400. You can buy the whole van, do your swap with a running vehicle, then scrap the rest.

  6. #6
    Senior member spectreblazer's Avatar
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    grey i run about 2500 rpm at 55. which seems about normal. i need to check vac lines, but i'm just thinking down the road as one of those projects that eventually pays for itself. let says i get the 350 running like it's suppose to. what would you say would be a fair mpg? 10?

    okay so a 4bt at the lowest would yield 20mpg. so that would be double. i saw one on youtube that a guy claimed he was hitting mid 20s.

    what would you think the swap would cost total? doing all the fab work myself, installation, etc. only cost would be parts.
    compared to the 6.2L. if i could find one with a turbo i would jump on it in a heart beat.


    2000 Saturn Sl1-daily driver

    1997 Ford F250 7.3L diesel

    1982 K-5 350 w/turbo 350/203-Play truck

    1984 K20 w/1 ton dually rear 6.2L turbo diesel w/700r4/208-Work truck/daily driver-coming soon

    1991 C10 suburban soon to be k10

    "Before you criticize a man, walk a mile in his shoes. That way, if he gets angry, he's a mile away and barefoot."

  7. #7
    Senior member trav0302's Avatar
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    Lets make this easier http://www.chevyk5blazer.com/forums/...ns-deisel-swap.. Alot of this post has already been said.

    Under the knife 1972 k5 350 4 speed
    Originally Posted by sevenn07
    "No K5 graveyard, they're all still running. lol"
    cell:303-895-7058 email:trav0302@hotmail.com

  8. #8
    A 6.2 swap would be a fraction of what a 4bt would be, as it uses the same bolt pattern on the tranny and motor mounts, but not near as cool. I don't know about your area, but a 4bt around here goes for $1,500-3k. A 6bt or 12 valve is cheaper, but requires a lot more beef fab. There is no real set cost on a build, it really depends on what you can make and what you have to buy. Whatever you think the build will cost, double it. Rule of thumb.

  9. #9
    The man, the myth, the legend adam89k5's Avatar
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    what tranny will bolt up to a crate 6.2 diesel? i might go that route too since theyre so cheap

    Its a rock, GET OVER IT!

  10. #10
    Unofficial Diesel Guru Senior member Koots's Avatar
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    The transmission you have in your blazer will bolt up to the 6.2L. It runs the standard chevy bolt pattern, also uses smallblock motor mounts.

    It definitely isn't that cool to run a 6.2L, but they can be had for super cheap. 6.5L turbo kits can be had anywhere from $300 used to $1000 new and will put you around 200HP and 400lb-ft torque. Mind you that exceeding this number (about 8-12psi of boost) will need to be met with more mods so that you don't blow shit up.
    1983 GMC Jimmy

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