84 CDV engine swap technical questions
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RWD 19xx-1984 DeVille and Fleetwood,
1985-1996 Fleetwood and Brougham Forum Discussion, 84 CDV engine swap technical questions in Past Cadillac Vehicle Discussion; Hello all, I have a 1984 coupe that currently has a reman HT4100 that runs good. I know that a ...
  1. #1
    fslay is offline Cadillac Owners Member
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    84 CDV engine swap technical questions

    Hello all,

    I have a 1984 coupe that currently has a reman HT4100 that runs good. I know that a lot of these cars were junked because of the bad motor design, and I want to keep my car as clean and original looking as possible. I've considered several engine swaps for the future, and out of all the features I'd like to keep on a potential swap motor is the fuel injection. I would really like to see about the feasibility of swapping in a stock 6.0L 368 and keep the digital fuel injection, probably with a computer from an original 6.0L car. I am not interested in the V8-6-4 stuff, but have located a factory EFI manifold for reasonable. All the engine accessories appear to be in the same location between the current 4.1 and the 368. I would like to use the TH400 from an 80-81 RWD as well as the rear end. I have located a donor car that is carbureted for most of the donor parts. Anybody got ideas? I really have no need for the 425, 472, or 500 as I will never use that much power. I am really looking more for reliability and solid design. Any ideas are greatly appreciated.

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    csbuckn is offline Cadillac Owners Master
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    Isn't the tbi unit and computer similar enough to a tbi SBC to run it? Seems the easiest to do if it works.

  4. #3
    85 FLEETWOOD COUPE's Avatar
    85 FLEETWOOD COUPE is offline Cadillac Owners Fanatic
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    Re: 84 CDV engine swap technical questions

    Get a rebult small block chevy fuel injected or even carbed,you will be so happy with the change, i wished all cadillacs had the chevy motors from factory

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    jayoldschool's Avatar
    jayoldschool is online now GM RWD V8 addict
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    Re: 84 CDV engine swap technical questions

    Spoken like a true noob.

  6. #5
    85 FLEETWOOD COUPE's Avatar
    85 FLEETWOOD COUPE is offline Cadillac Owners Fanatic
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    Re: 84 CDV engine swap technical questions

    Who u talking to?

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    cadillac kevin's Avatar
    cadillac kevin is offline Cadillac Owners Master
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    Re: 84 CDV engine swap technical questions

    the guy who wants every caddy to have an SBC under the hood.

  8. #7
    The Ape Man's Avatar
    The Ape Man is offline Cadillac Owners Connoisseur
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    Re: 84 CDV engine swap technical questions

    I've done this swap. It was done 19 years ago so I might not remember everything : )

    Most of this is obvious stuff so I'll throw out a few items which were not obvious to me.

    The 368 throttle body is larger.

    Get the driveshaft from the 3 speed car.

    The steering column shifter detents on the 4 speed car will feel funny hooked to the TH-400 but you can adjust N in the right place and even a woman can drive it. I've swapped columns but this can get painful.

    The HT-4100 ECM will need to be swapped. Sometimes the pinout is not plug and play to an 8/6/4 ECM. Have the 8/6/4 wiring available.
    If I were doing this swap today I'd just get a Megasquirt kit and ditch the factory system.

    You will need the entire 8/6/4 exhaust system and A.I.R. plumbing for the factory ECM to give you the right time of day. The carbonated 368 exhaust lacks the 3 way catalyst and hard to find valve assy.

    You can keep the HT-4100 radiator and fan clutch if they are OK. They are actually better than the 368 pieces.

    There's more...............

  9. #8
    fslay is offline Cadillac Owners Member
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    Re: 84 CDV engine swap technical questions

    Ape Man,

    I was relieved to hear that somebody had done this swap before. Let me ask you this...if I decided to swap in the 368 and go with a carburetor, would this make the swap easier or would it just complicate things more? I could probably live without the digital fuel injection, but i didn't think about the fact that the dfi cars also had the modulated displacement too. I just want to be able to open the hood and things not look chopped, so to speak. I want things to look clean and factory looking. I'm not above the carburetor if that simplifies things. Please feel free to chime in if you got anything else, as its greatly appreciated


    To the others who responded about the SBC...I like the 350 but I want a cadillac motor in my cadillac. I guess its a purity thing. Your comments are greatly appreciated as well

  10. #9
    j2rossit is offline Cadillac Owners Enthusiast
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    Re: 84 CDV engine swap technical questions

    The carburetor would be hidden under the air filter, so I would expect it wouldn't look out of place. As Ape Man said, the 4100 throttle body doesn't allow the air flow required for the bigger engines.

  11. #10
    The Ape Man's Avatar
    The Ape Man is offline Cadillac Owners Connoisseur
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    Re: 84 CDV engine swap technical questions

    The answer depends on your parts sourcing. If there's an 8/6/4 car I say go for it. The MD only includes the tall rocker covers and solenoids as far as looks go.

    If you have a 368 with original distrubutor curve and carbonater calibration there's hope for OK economy. Probably best to go with an engine mounted fuel pump and remove the tank pump. I've done it both ways.

    If none of this stuff is available to you consider an aftermarket injection system. The Megasquirt was pretty cheap but labor intensive.

    Whatever you decide the people here can save you some time and expense.

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