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Thread: Carb? TBI? MPFI?

  1. #1
    5.7L VORTEC 350 blazin4low's Avatar
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    Carb? TBI? MPFI?

    Pros and Cons of a Carb, TBI, or MPFI swaps

    I have an agrument on another forum about this right now, and I know a few on here that have gone TBI to carb, carb to MPFI, TBI to MPFI.

    so my question is what are the pros and cons of each, and out of those that have swapped from one to the other, which swap was easyer?

    I'm going to do some digging, but for now I will throw this out there.....if we get some good responses this could be a sticky to kill future "How hard is it to swap...." threads
    http://i158.photobucket.com/albums/t114/VortecBlazer/sidredo.jpg
    Tuned by Bland Tuning
    Transmission built by Transbuilderguy on FSC!
    Marine Intake swap by me

  2. #2
    Zombie Killer 6SpeedBlazer's Avatar
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    i have done a tbi to tbi swap and the damn thing never ran right even though it was a stock motor with a small stock (from another vehicle) cam. i got tired of dealing with outdated technology and tuning software that never worked right. so i went with something newer.

    i got all my vortec 5.7L stuff for free so i went that route. i swapped it all in and even with a large cam and roller rockers the truck fired up the first try and ran better then my old stock tbi setup.

    for me the vortec 5.7L swap easier than the tbi swap was. however i was going from a v8 to a v8, which isnt exactly rocket science.

    i decided to go with fuel injection for many reasons. the first being emissions. my truck is 50 state emission legal the way it sits right now. i would even bet that i could pass a sniffer test if i had to.

    the second reason is drive ability. my tbi 5.7L never ran right and would even surge at cruising speed. it was bitch down in the low gears and at stoplights/signs. the vortec 5.7L even with a cam runs and drives like stock. just ask my mother she drives it on occasion.

    the last reason is fuel mileage. my truck averages about 24-25mpg highway if i drive it nice. dicking around im closer to 20mpg.

    i think a lot of people go with carb swaps because they are afraid of technology and start to feel overwhelmed by all the wires, sensors, and whatever else. in reality if the person is a halfway competent gear head and can read wiring diagrams they will understand that it only takes 3-5 wires to make any gm harness stand alone and another 5 or so wires to get the factory gauges to work.

    engine technology has come a long way since 1970 and it has even made leaps and bounds in the past ten years.

    there have been a couple guys that have swapped 5.3L's into zr2 trucks and are getting 25ish mpg. factory they are rated at 19mpg. my truck gets about 18.4 on average.

    there are even guys swapping lsx series motors and getting 25-30mpg in second gen trucks.

  3. #3
    Senior Member bigjsp's Avatar
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    Part of the issue is that too many people "think" they know carburators.

    So far all my swaps are technology simple using the same electronics from the engine/tranny donor vehicle.

    Next project's motors will be more fun being turboed, upsized injectors etc...

  4. #4
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    went 4.3 tbi to 5.7 tbi, it was almost a direct engine swap, minus extending a few wires, swithcing a prom, and injectors...

    then resessing the rad, and then fitting headers but that would be no different than a stock motor...

    ran great after i tuned it, ran like stock. Got about 3 miles per gallon less than the stock 4.3 got. But it was worth the added power. May have been able to get the same if i were a good tuner but all i was just good enough to get it to run like a stock tbi engine. had an lt1 cam in it.


    Then i switched to carb for reasons, I dont have a choke, so cold start i have to baby it along for half a min or so, and even with a heat dissapaiter gasket i still have a heat soak starting issue every once in a while. but other than that it runs, id still prefer efi, but i cant say the carb doesnt work.

    Took more time to convert from tbi to carb than it did going from v6 to v8 tbi seriously.


    89' S10 blazer 4wd: 355, 650 dp, rpm intake, comp 282 roller cam, modified vortecs, T56 Six speed, 8.8 ls rear, headers, x-pipe, spintech pro street mufflers, and......AC

    Blazer burnout video - http://www.youtube.com/watch?v=sP7iLypoDI4

  5. #5
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    and real fast

    carb- you can just slap it on any motor and go. Can have drivability issues efi doesnt have. can have worse milage
    tbi- great for a stock motor, but has to be tuned with any modification, has hp limitations.
    mpfi- doesnt have the hp limitations like a tbi unit does. can cost more, takes more time to install. Best milage


    89' S10 blazer 4wd: 355, 650 dp, rpm intake, comp 282 roller cam, modified vortecs, T56 Six speed, 8.8 ls rear, headers, x-pipe, spintech pro street mufflers, and......AC

    Blazer burnout video - http://www.youtube.com/watch?v=sP7iLypoDI4

  6. #6
    Zombie Killer 6SpeedBlazer's Avatar
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    Quote Originally Posted by Superbee View Post
    and real fast

    carb- you can just slap it on any motor and go. Can have drivability issues efi doesnt have. can have worse milage
    tbi- great for a stock motor, but has to be tuned with any modification, has hp limitations.
    mpfi- doesnt have the hp limitations like a tbi unit does. can cost more, takes more time to install. Best milage
    i bet i had my MPFI swap running in less time than it took you to convert to carb.

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