84 coupe deville 4.1 or 350.
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RWD 19xx-1984 DeVille and Fleetwood,
1985-1996 Fleetwood and Brougham Forum Discussion, 84 coupe deville 4.1 or 350. in Past Cadillac Vehicle Discussion; I recently got an 84 coupe deville with a 4100. Im trying to decide if I want to drop in ...
  1. #1
    chuck84 is offline Cadillac Owners Member
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    84 coupe deville 4.1 or 350.

    I recently got an 84 coupe deville with a 4100. Im trying to decide if I want to drop in a 350 or rebuild the 4.1. I have a mechanic that told me he would rebuild it and replace the sleeve and everything. I asked him about the over heating issues and he said he can build it and I'd never have to worry about it over heating and it would run like a sewing machine. Any thought? I like the fact it would still be all original, it's just what about the power!

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    Angry Matt's Avatar
    Angry Matt is offline Cadillac Owners Enthusiast
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    4100's are dogs. I drove one of mine to Kentucky once and all across southern PA it would struggle up the mountains. It had about as much umpf as the international box truck I drive every day.

  4. #3
    drmenard is offline Cadillac Owners Connoisseur
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    Re: 84 coupe deville 4.1 or 350.

    I would never own another 4100 . If you fix the one you have now you will be sorry , sooner that later... I have a friend who is a used car dealer.. He used to buy these cars used with low miles just because the motor made noise and the people were sick of the low power.. The would change the main bearings with .001 under bearings and it would quiet the rumble in the motor and he sold them... then they ran ok for 8 to 10 K ... Do yourself a favor and find a donnor junk FWB with a 350 and put the motor and trans right in..

  5. #4
    the APEMAN is offline Cadillac Owners Fanatic
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    Re: 84 coupe deville 4.1 or 350.

    The HT-4100 does run like a finely tuned watch when it runs.

    Cadillac decided to keep the RWD line several years longer than original plan.

    Problem was engines were in short supply.

    They designed a patch to make the brand new front wheel drive HT-4100 engines work in the old RWD chassis.

    The quick fix compromised block strength.

    Heavier cars and weak blocks produced dealership parts departments full of warrantee engines in crates. I was there.

    It also wrecked many dealership mechanic's careers as they were severely shortchanged on engine replacement times.

    Stay far away from these engines in a rear wheel drive vehicle. They will make an excellent mechanic out of you and drain your bank account. Weakling cars will laugh at you at stoplights.

    The upside to all this was perfect car bodies just waiting for drivetrain retrofits. Funny how a 500 C.I. Cadillac engine is exactly twice the displacement of an HT-4100.

  6. #5
    93Fleetbrougham93's Avatar
    93Fleetbrougham93 is offline Cadillac Owners Member
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    Re: 84 coupe deville 4.1 or 350.

    I had a 4100 in a cant remember what year fwb......man, I could barely merge into traffic to get on the freeway during rush hour and im not exaggerating! sold it 3months later & got a 1995 deville with a 4.9. One of the best cars I've ever driven. My vote is to swap in the 350.

  7. #6
    the APEMAN is offline Cadillac Owners Fanatic
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    Re: 84 coupe deville 4.1 or 350.

    Quote Originally Posted by 93Fleetbrougham93 View Post
    I had a 4100 in a cant remember what year fwb......man, I could barely merge into traffic to get on the freeway during rush hour and im not exaggerating! sold it 3months later & got a 1995 deville with a 4.9. One of the best cars I've ever driven. My vote is to swap in the 350.
    And the 4.9 is a refined 4.1 which proves it can be made to work.

  8. #7
    talismandave's Avatar
    talismandave is offline Cadillac Owners Master
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    Re: 84 coupe deville 4.1 or 350.

    Quote Originally Posted by the APEMAN View Post
    And the 4.9 is a refined 4.1 which proves it can be made to work.
    ....eventually, after a lot of attempts!
    bigm57ict likes this.

  9. #8
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    Re: 84 coupe deville 4.1 or 350.

    Chevy 350 is a decent swap into a 4100 powered car. Problem is you will soon be replacing the 200R4 trans because it can't take the added power. Plus the 4100 cars came with the weak 7.5" 10 bolt rear end. Keep the power below 300hp and don't drag race it and you'll be fine with that rear end.

    If it were my $$$$ I'd swap in a high compression Cadillac 500/turbo400 tranny combo, upgrade to a 12 bolt rear end. Or maybe a big block Chevy, one of those 572 crate motors would move you along real nice if $$$$ were no object. But a mild Chevy 350/700R4 out of a newer truck makes a good budget replacement.

  10. #9
    the APEMAN is offline Cadillac Owners Fanatic
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    Re: 84 coupe deville 4.1 or 350.

    Most retrofits were Olds. None of my retrofits were anything but Cadillac : )

    The 2004R lived behind Buke turbo cars making lots of power but they had special pumps and other hard to get stuff.

    I had two behind Cadillac 500s because my transmission guy at the time said they would work OK. They didn't.

    The original HT-4100 RWD rear ends were useless because they weren't posi so weakness just added another reason. Were they really 7.5" ring gear? I always thought they were a little better.

    Big block Chevy is a fine powerplant with a different purpose than a Cadillac 500. the Cadillac engines were designed to haul a 5000 lb car around using crummy gasoline with some emissions gear without performance loss compared to older barges. They were also required to deliver decent economy.

    The Chevy engine was designed with a lot less thought of economy. They are easier to modify for more power and hold up very well.

  11. #10
    j2rossit is offline Cadillac Owners Enthusiast
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    Re: 84 coupe deville 4.1 or 350.

    If I were you I'd ditch the original engine and try and find a good used 4100 Goodwrench replacement engine. They were released after the originals and have most of the problems fixed. You can over heat them and they will bounce right back. This would also allow you to save all the working electronics and diagnostic features. I've got one in my 85 and I'm about to get my buddies 82 with a Goodwrench engine. It's been his daily driver for years and it will be my wife's semi weekly driver.
    grauhst likes this.

  12. #11
    Lord Fleetwood is offline Cadillac Owners Member
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    Re: 84 coupe deville 4.1 or 350.

    The HT 4100, if rebuilt correctly, can be reliable. My first car was an 83 Coupe DeVille with an already rebuilt 4100. I got it in 98 and had it for 5 or 6 years and only got rid of it due to a rust hole in the frame. I would have even fixed that, but I was a poor college boy in my early 20s and couldn't really find anyone who would do it, let alone get a reasonable price. The engine never once gave me trouble the entire time I owned it.

    That said, the car was a dog. It was quite slow and didn't like hills. As mentioned before, it was never meant to be in these big rear-drive cars. It was designed to be used in the majorly-downsized 85 DeVilles which were supposed to come out sooner than 85. It did a good job moving those cars, but they were much smaller and lighter. I remember everybody thinking my 83 CDV had a big motor and could move, but it couldn't. An old guy at a shop was talking to the mechanic and was looking at my car and wanted to know if it had a 7-liter in it. I cringed and the mechanic simply said no, it was smaller. The old guy was like "it's gotta have at least a 5-liter" and then the mechanic told him it had a 4.1-liter engine and the guy was completely taken aback. Piece of crap four-cylinder cars would beat my poor CDV on too many occasions (it always beat those Dodge Neons, though). So, even though the engine can be made reliable, the low power output isn't worth it and should be changed out if you have the opportunity. The only plus was that it did have decent gas mileage considering. It would get 24 mpg on the highway and around 17 in town (measured by me, not by the fuel data center).

  13. #12
    csbuckn is offline Cadillac Owners Master
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    Makes me want to get a 4.1 engine just to take it apart and see if I can make it reliable. What did the goodwrench 4.1 change to fix it exactly?

  14. #13
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    Re: 84 coupe deville 4.1 or 350.

    The gas mileage was the only good thing about the HT4100.

    I put about 60,000 on mine before it stated burning anti-freeze. Was fine around town, and great on the freeway, but "quite slow and didn't like hills" is being generous!

    Passing on a two lane road was a white-knuckle event!

    That said, I would own another one. Lived with it for 5 years, and just got used to the limitations.

  15. #14
    j2rossit is offline Cadillac Owners Enthusiast
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    Re: 84 coupe deville 4.1 or 350.

    Quote Originally Posted by csbuckn View Post
    Makes me want to get a 4.1 engine just to take it apart and see if I can make it reliable. What did the goodwrench 4.1 change to fix it exactly?
    The main things that I know of are they changed the bracing in the block to stop it from eating head gaskets. Increased the size of the main bearings to stop the issues of wearing out prematurely. They did something to keep the cam bearings from spinning.
    Pretty much the only problem that I know of that plagued the original engines that didn't get fixed is the aluminum oil pump was still just as prone to wear out early. It's a big job to do it when the engine is in the car, but if you're doing an engine swap, it would be real easy to put in a new oil pump prior to doing the swap.

  16. #15
    Lord Fleetwood is offline Cadillac Owners Member
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    Re: 84 coupe deville 4.1 or 350.

    Quote Originally Posted by talismandave View Post

    I put about 60,000 on mine before it stated burning anti-freeze. Was fine around town, and great on the freeway, but "quite slow and didn't like hills" is being generous!

    Passing on a two lane road was a white-knuckle event!
    I'm not the type to hit a man when he's down, but since you went there, acceleration, especially at high speeds or on hills, was horrendous. I remember pulling the ol' Coupe DeVille out onto a road with a rather long and steep hill with a mid-90s Pontiac Grand Prix behind me. I really tried to get up that hill in hopes the Pontiac wouldn't want to dust me, but the Pontiac passed me like I standing still. The guy was up and over that hill before I was even a third of the way up and still trying to get up to speed. That small engine looked so out of place in that big bay. I would also own another, but I would never keep the engine. That CDV was a great car in pretty much every other way and deserved so much better than the HT 4100.

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