what engine is in the 81 coupe deville
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500, 472, 425, 368 Discussion, what engine is in the 81 coupe deville in Cadillac Engine Technical Discussion; I'll be getting another car soon and theres a 81 coupe deville for sale. Anyone know what it has under ...
  1. #1
    DeVillish's Avatar
    DeVillish is offline Cadillac Owners Connoisseur
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    what engine is in the 81 coupe deville

    I'll be getting another car soon and theres a 81 coupe deville for sale. Anyone know what it has under the hood? I hope its not a 4.1.

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    lux hauler is offline Cadillac Owners Connoisseur
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    I don't think they started using the 4.1 until '82.
    The '81 should have a 368, I believe.

  4. #3
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    Re: what engine is in the 81 coupe deville

    "The '81 should have a 368, I believe"

    and hopefully not the 8-6-4

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    lux hauler is offline Cadillac Owners Connoisseur
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    Someone correct me if I'm wrong but.......don't the 368 and the 4-6-8 (8-6-4) use the same block? It was the electronics that made them different, right?

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    Re: what engine is in the 81 coupe deville

    Quote Originally Posted by lux hauler
    Someone correct me if I'm wrong but.......don't the 368 and the 4-6-8 (8-6-4) use the same block? It was the electronics that made them different, right?


    I believe you are correct. I heard that some folks would dump that electrical gremlin.

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    ´81 De Ville had three engines
    - Buick´s V6 252cid, 125bhp
    - troublesome V8-6-4 368cid, 140bhp
    - and optional diesel engine - 350cid, 105bhp

  8. #7
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    Re: what engine is in the 81 coupe deville

    Quote Originally Posted by vanaisa
    ´81 De Ville had three engines
    - Buick´s V6 252cid, 125bhp
    Don't you mean the 231 V6? A buick 4.1? Never heard of it!

  9. #8
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    Re: what engine is in the 81 coupe deville

    Quote Originally Posted by 2dfx
    Don't you mean the 231 V6? A buick 4.1? Never heard of it!
    yep - Buick. I was "economy option":lol
    90-degree, overhead valve V-6. Cast iron block and head
    252 cu. in. (4.1 liters)
    Bore and stroke: 3.965 x 3.40 in.
    Compression ratio: 8.0:1
    125bhp at 3800 R.P.M.
    Torque: 210 lbs.-ft. at 2000 R.P.M.
    4-bbl carburetor

  10. #9
    lux hauler is offline Cadillac Owners Connoisseur
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    Quote Originally Posted by vanaisa
    ´81 De Ville had three engines
    - Buick´s V6 252cid, 125bhp
    - troublesome V8-6-4 368cid, 140bhp
    - and optional diesel engine - 350cid, 105bhp
    It looks as though you are correct.
    http://100megsfree4.com/cadillac/cad1980/cad81d.htm
    Standard engine for DeVille and Fleetwood Brougham was the "modulated displacement" 368 cu. in. (6.0-liter) V8-6-4, with digital fuel injection. Optional: a 252 cu. in. (4.1-liter) V-6, provided by Buick. That V-6 had Computer Command Control and a knock sensor to adjust spark advance, as well as diagnostics. The Olds diesel V-8 was also offered.
    I guess the 368 was never offered any way except in the V8-6-4 configuration.
    It looks like the Buick V6 was the best engine offered.

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    If I recall, the 368 was without multi-displacement (MD, 8-6-4) in '80, in '81 the FW limos, and in the commercial chassis in '81-'83. The 368 MD was in all models except limos/commercial in '81, and then in limos from '82-'84.

    I'd rather have a 368MD than the Buick V6 because I'm pretty sure the MD can be disabled (although some people find it to work fine). Plus it would probably be easier if you ever feel like swapping a 500/472 in. The Buick V6 and the HT4100 just don't put out enough power for a 2 ton Cadillac in my opinion.

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    Re: what engine is in the 81 coupe deville

    The Buick V6 CAN actually be beefed-up quite easily, and YES it was 4.1 liter 4bbl. The 368 was available with or without the MD gear depending on the year. As I recall, the '80 was the NON-MD and the '81 was MD. We had all Fleetwood Formal Limos back then as for Cadillacs and our 81's had the MD. And it IS very easy to disable.

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    Re: what engine is in the 81 coupe deville

    ive heard alot about the buick 4.1 v6 , and ive heard it was available as a turbo in some buicks , ill do some research on it after a bit , why this never took off i dont know i imagine a 4.1 turbo would give more torque than the 3.8 turbo in later turbo buicks (outside gnx)


    EDIT !!!!
    Yes , there was a 4.1 turbo v6 , couldnt remeber where i heard of it , it was int he buick rivera indy 500 pace car , apperently it was the only 4.1 turbo ever made and since Tom Sneeva probably got it after winning the 500 (the winner ususly gets the pace car or a replica ) , the riveras probably in a museum somewhere or if sneeva didnt get it its probably in the back of a GM wharehouse sitting next to the 85 fireo pace car and a couple of beretta convertables from the 1990 500

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    Re: what engine is in the 81 coupe deville

    OK, Here is the real scoop on the V-864. The non modulated version of this engine WAS installed in the 1980 model. Apparently all of the electronics were not worked out yet. In 81, they went full force with this thing. It had digital fuel injection, electronic on-board diagnostics AND an analog back-up computer if anything went wrong.

    I found the system to be very reliable and drove my 81 Fleetwood 330,000 miles with NO trouble. As a matter of fact, the second owner of this car since I sold it is STILL driving it. The only thing he has replaced on the motor is the distributor drive gear. 420,000 miles!!!

    As for disabling the system, this is very easy. The key is knowing how the thing works to begin with. The computer measures load/torque requirements and when conditions are right, begins to shut off cylinders. This is accomplished by rotating a turret shaped contraption above the rocker arms allowing the rocker to raise up from the head. This action leaves the valve closed on that cylinder. With the valve closed, the same air/fuel mixture is continuously re compressed, keeping the cylinder temperature up and of course, not taking in any more fuel.

    The key is that NONE of this happens until the car is at cruising speeds. This was determined by a signal from the transmission that it was in high gear. To disable the system, reach under the car and from the driver's side and snatch the 2 wire connector from the side of the transmission... you now have a full time V8. No codes, no lights, no problem.

    Now what I did that I thought was a bit more elegant was to intercept this wire with a switch at the dashboard. It is simply a ground signal to the computer so no fancy voltage crap is required... just splice and go. With the switch in place you can run V8 as much as you want and then when you get stuck in the middle of nowhere looking for a gas station you can flip it on and return to the "32 mpg mode"

    As for the complaints from the general public... hell it was new and everyone complains about that. At the time, American cars with 4 cylinders engines just were not good PR, especially in a Caddy. The other problems again had to do with the operation of the system. When you got up to moderate speeds the car would shift from 8 down to 6 and finally to 4 cylinders. The 6 cylinder mode was unbalanced feeling even though it was only in this mode for short periods of time. I think they would have been bettter off to have it drop from 8 to 4 like they do now. (YES, this is how today's Northstar engine handles driving without coolant, exept both valves are OPEN instead of closed) The other thing that made driving this a bit uncomfortable was the fact that when you coast to a stop, there is always that point when the governor in the transmission shifts down from 3rd to 2nd gear. In most automatics, you never feel this happen. At this point the engine was instantly returned from 4 cylinder operation to 8, creating a slight surge even at zero throttle. If you are not comfortable with the car and have a really light braking foot (typical 70yr old demographic) this could be scary.

    Remember that the 368 is just a smaller bore version of the bulletproof 425 engine used from 77 up to 80. Buy the 81, complain about the V864 to get the price down, take it home, snatch a wire, and drive the hell out of that car. It will do good for you. If you really want something good, hold out for a Fleetwood Coupe. These things are getting REALLY rare.

  15. #14
    Stoneage_Caddy's Avatar
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    Re: what engine is in the 81 coupe deville

    GOOD POST !!!!

    i never knew much about the 864 , or its operation , just the grumbles over quaility

    as for nowaday uses it found a home in a upcoming 5.3 litre chevy truck engine , i think gm is getting ready to stick these in silverados

  16. #15
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    Re: what engine is in the 81 coupe deville

    I'm telling you, is this guy a wealth of knowledge or what?
    Great post Bill.

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