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HT4100 4.1, 4.5, 4.9 Discussion, New Member Introduction in Cadillac Engine Technical Discussion; Good afternoon all. I have joined this group in the hopes of finding some other members who have had tried ...
  1. #1
    Robin Banx's Avatar
    Robin Banx is offline Cadillac Owners Fanatic
    Automobile(s): 1983 Fleetwood Brougham
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    Dec 2007
    Location
    Vancouver, B.C. Canada
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    New Member Introduction

    Good afternoon all. I have joined this group in the hopes of finding some other members who have had tried to swap out the dreaded HT4100 engine in favour of a more reliable power plant. I have a nearly-new 1983 Fleetwood Sedan DeVille with the disgraceful 4.1 litre V8 engine. The car has rolled only 27,000 miles since new and is otherwise similar to a car which has been driven only about two and a half years in its life thus far. I am awaiting the day when my engine begins to make the fatal "milkshake" in the oil pan and ultimately destroys itself. I have been told that it is impossible to replace this motor with anything other than a replacement HT4100. I cannot believe this to be true. Has anyone successfully swapped anything into one of these cars successfully.

    Cheers..........R.B.

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  3. #2
    pompste is offline Cadillac Owners Connoisseur
    Automobile(s): 1995 SEDAN DEVILLE-4.9 & 1978 SEDAN DEVILLE-425
    Join Date
    Jan 2007
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    Re: New Member Introduction

    Quote Originally Posted by Robin Banx View Post
    Good afternoon all. I have joined this group in the hopes of finding some other members who have had tried to swap out the dreaded HT4100 engine in favour of a more reliable power plant. I have a nearly-new 1983 Fleetwood Sedan DeVille with the disgraceful 4.1 litre V8 engine. The car has rolled only 27,000 miles since new and is otherwise similar to a car which has been driven only about two and a half years in its life thus far. I am awaiting the day when my engine begins to make the fatal "milkshake" in the oil pan and ultimately destroys itself. I have been told that it is impossible to replace this motor with anything other than a replacement HT4100. I cannot believe this to be true. Has anyone successfully swapped anything into one of these cars successfully.

    Cheers..........R.B.

    Hi there! Just some friendly advice here-----you may want to post your request in the RWD DEVILLE & FLEETWOOD FORUM if you want a quicker response.More people view that forum than this one.
    Good luck!

  4. #3
    awadecki is offline Cadillac Owners Enthusiast
    Automobile(s): 76 Eldo (54k), 76 Eldo (52k), 78 Eldo (9k), 85 Deville (43k)
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    Jun 2005
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    Re: New Member Introduction

    Hi--

    Well, first of all, if you catch the "milkshake" early, you should be fine.

    On another note, I'd think that you could easily swap a Cadillac 425 or 368 in there, or an Olds 350 gas (or even diesel) V-8. All were used in that vehicle, except the Olds 350 gas engine, which is identical in size to the diesel, which was offered.

    You will need new wiring harnesses and a different transmission, though. The HT4100 used the 200r4, while the others used a THM400.

  5. #4
    noahsdad's Avatar
    noahsdad is offline Cadillac Owners Connoisseur
    Automobile(s): '87 SDV
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    Jun 2005
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    Michigan
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    Re: New Member Introduction

    Other than being underpowered for the big body (which it was not designed for), the vast majority of 4100s in the early installations hummed along just fine into the 120k range, and most of the major failures at that point were transmission related. The key is following the coolant change schedule to the letter, and driving it respectfully.
    If you dislike the 4100 that much, it's not worth the trouble and expense of a swap. There are plenty of low mileage big body DeVilles around with a standard V-8.

  6. #5
    Po Pimp is offline Cadillac Owners Fanatic
    Automobile(s): 92' Eldorado, 97 Catera
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    Re: New Member Introduction

    People who drive the car after the two have started mixing are the ones that have the severe problems like say a camshaft snapped in two. Doing the maintaince and a visual check once a week eliminates this concern more then anything. Also remember if you catch them quick they are also generally cheap and somewhat easy to fix. I agree with the underpowered part quicker then I would unreliable.

    Things I have seen in a RWD Caddy like yours:

    Small block and big block Chevys
    Big block Cadillacs
    Oldsmobile small blocks
    60* 3.8L Turbo Buick (this one was quite interesting)

    I really do not think any of these are cheap. All but one of these I saw where show cars. Not really daily drivers. THe one that was not a show car had a SBC.

  7. #6
    ehall's Avatar
    ehall is offline Cadillac Owners Connoisseur
    Automobile(s): 1985 Sedan DeVille
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    Southern Maryland
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    Re: New Member Introduction

    You can run almost any engine you want in that, since it's RWD. You might need to do some fab work but it should be pretty straightforward. From what I understand, the 425 is a drop-in for yours but you should ask in the RWD forum.

  8. #7
    Po Pimp is offline Cadillac Owners Fanatic
    Automobile(s): 92' Eldorado, 97 Catera
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    Tennesse
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    Re: New Member Introduction

    Basically anything that will mount to that tranny and drop in that car easily will be weak. The tranny can not handle much additional torque safely. There are some options. They also weight more with minimual gains (say 15-30hp) for the addition of 70-100lbs engine weight. Not worth it.

    If you go all out custom there are many options but $$$/your skills will decide the outcome.

  9. #8
    Robin Banx's Avatar
    Robin Banx is offline Cadillac Owners Fanatic
    Automobile(s): 1983 Fleetwood Brougham
    Join Date
    Dec 2007
    Location
    Vancouver, B.C. Canada
    Posts
    406

    Re: New Member Introduction

    Thanks guys, for the input. Since joining the group and surfing for info for my 83 F'wood, I am a now bit the wiser. I may well have condemned the HT4100 engine in my car without a fair trial. It has yet to show any sign of disaster and is far and away the smoothest motor I have ever driven. It moves my car about the streets of Vancouver with great diginty and style and at a pace commensurate with my advancing age. I think that rather than looking at replacing it, I should perhaps be looking at ways in which to stretch its life to the max. Much as my doctor is currently doing with me. I have learned that one way to prevent the coolant from leaking into the crankcase is to re-torque the headbolts regularly as their coming loose is the chief cause of the "milkshake" making.
    The next thiing I need to learn is how to post pix on this website. Some folks might be interested in seeing photos of what well might be the lowest mile D body outside of a museum and also a 4-6-8- sedan deville that still works like a charm and will run from Vancouver to Kimberley B.C. on one tank of gas.

    Thanks again for your interest....R.

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