Ht4100 to 350 tbi swap
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5.0 and 5.7 Discussion, Ht4100 to 350 tbi swap in Cadillac Engine Technical Discussion; I tried to have some faith in the HT4100 until I actually got it running. I'd always heard how underpowered ...
  1. #1
    sholford is offline Cadillac Owners Member
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    Ht4100 to 350 tbi swap

    I tried to have some faith in the HT4100 until I actually got it running. I'd always heard how underpowered they were, but I didn't realize it was that bad. My '78, 305 powered LeMans felt fast after driving the Fleetwood.

    Well anyway, has anyone swapped the 350 TBI into a HT4100 powered car? I came across a '91 donor car with the 5.7 setup. Since I can't find anything on the web about it, I plan to make a webpage out of the whole ordeal when I'm done. My main concern is the wiring, sensors, and fuel system. If anyone has done this or has any info, I would appreciate it. The reason I want to go with the 350 is because it's fuel injected and has decent power. The 500 or 472 swap will kill me on gas in Chicago, not to mentioned, I'd like to keep the overdrive.

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  3. #2
    joe_padavano is offline Cadillac Owners Member
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    Re: Ht4100 to 350 tbi swap

    What's the car model and year?

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    sholford is offline Cadillac Owners Member
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    Re: Ht4100 to 350 tbi swap

    '83 Fleetwood coupe. I've been debating whether I should go with a cad 500, a 350 tbi, or an olds 350/403. I'm leaning towards keeping the fuel injection, although it may be a little more trouble concerning the wiring. Besides, gas is getting crazy in Chicago, not to mention the unpredictable weather.

  5. #4
    N0DIH's Avatar
    N0DIH is offline Cadillac Owners Master
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    Re: Ht4100 to 350 tbi swap

    With the gas prices like they are, I would probably stick with the TBI 350..... Olds 350's are good too....

  6. #5
    Tommy Deville's Avatar
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    Re: Ht4100 to 350 tbi swap

    why would you losw Over drive with a 472 or 500 setup?

  7. #6
    N0DIH's Avatar
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    Re: Ht4100 to 350 tbi swap

    There is no OD that can handle the power of the 472/500. A 4L80E would probably survive, but they aren't cheap. Probably take 5 years of driving to offset the mpg gains vs fuel savings.... But a stock THM200 4R would die the first time you punched it.

    Well, there is a GearVendors OD, but they are $$ too....

  8. #7
    carnut is offline Cadillac Owners Master
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    Re: Ht4100 to 350 tbi swap

    The easiest TBI to install is off the 81 368 C.I. engine from Cadillac. Same idle speed motor mounting, same bolt circle, same mounting holes for the TPS. I did this swap years ago on my 84 Eldo. The throttle blades are much larger so you will have less throttle movement for the same power. You need the thick base gasket from the 368 so the throttle blades dont hit the intake or you can bore out the 4100 intake. Set the timing to 12 instead of 10 degrees. Make sure and swap over the 4100's injectors! the 368's flow too much fuel and will super heat the cat. converter!

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    3141592654 is offline Cadillac Owners Member
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    Cool CHEVY, not Olds!

    If you want to go with the 350 cid, I'd recommend the Chevy. It will bolt right up to the THM 2004R (Unicase on Caddies in these years). Also, the upfront cost will be less than the Olds because of availability. Also, so MUCH more aftermarket parts.

    find a Chevy "four-bolt main" engine out of a truck and you got it made!

    pi-

    P.S. Pitch the HT4100 in the weeds!

  10. #9
    The Ape Man's Avatar
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    Re: CHEVY, not Olds!

    Quote Originally Posted by 3141592654 View Post

    P.S. Pitch the HT4100 in the weeds!
    You can't do that. Cops will trace the brown gunk oil and water mixture right back to your house.

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    3141592654 is offline Cadillac Owners Member
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    Re: CHEVY, not Olds!

    Quote Originally Posted by The Ape Man View Post
    You can't do that. Cops will trace the brown gunk oil and water mixture right back to your house.
    ROFL, Ape Man. Apparently, the cops in your parts are smarter than mine.

    pi-

  12. #11
    The Ape Man's Avatar
    The Ape Man is offline Cadillac Owners Connoisseur
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    Re: CHEVY, not Olds!

    Quote Originally Posted by 3141592654 View Post
    ROFL, Ape Man. Apparently, the cops in your parts are smarter than mine.

    pi-
    Everyone knows there's only one thing that produces brown gunk in gallons.

  13. #12
    MadCaddie69's Avatar
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    Re: Ht4100 to 350 tbi swap


  14. #13
    MadCaddie69's Avatar
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    Re: Ht4100 to 350 tbi swap


  15. #14
    N0DIH's Avatar
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    Re: Ht4100 to 350 tbi swap

    Didn't Jeff sell it just in the last year? I think he posted here the sale ad....

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