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RWD 19xx-1984 DeVille and Fleetwood,
1985-1996 Fleetwood and Brougham Forum Discussion, 81 Coupe DeVille Engine swap in Past Cadillac Vehicle Discussion; Ok after much consideration, I think that I am going to sell the chevy 350 that I have and buy ...
  1. #16
    asaddman is offline Cadillac Owners Member
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    Re: 81 Coupe DeVille Engine swap

    Ok after much consideration, I think that I am going to sell the chevy 350 that I have and buy me an olds 350 to go in there, from what everyone has mentioned on here it sounds like it should just drop right in, shouldn't have to change motor mounts or anything like that, trany should bolt up too then right? Does that sound right to all you pros out there? SHouldn't have to do much else other than bolting her in?

  2. #17
    cadillac kevin's Avatar
    cadillac kevin is offline Cadillac Owners Master
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    Re: 81 Coupe DeVille Engine swap

    it should work pretty smooth. the olds 350 will bolt directly up to the transmission. I'm not sure if you'll have to change the motor mounts but if you do have to change them its not that hard or expensive.
    I think the AC compressor will bolt up to a olds motor so you should be able to keep AC.
    go for a olds 350 from 68-72. you get good power (300hp), and mileage is decent (for a 40 y/o motor coupled to a 3 speed trans). only downside is they're more expensive to buy and build up than a chevy motor. around here, 68-72 olds long blocks go for $400-$800 (depending on mileage, running or not, etc.) whereas a chevy long block (usually low output) go for $300-$500.

  3. #18
    asaddman is offline Cadillac Owners Member
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    Re: 81 Coupe DeVille Engine swap

    Quote Originally Posted by cadillac kevin View Post
    only downside is they're more expensive to buy and build up than a chevy motor. around here, 68-72 olds long blocks go for $400-$800 (depending on mileage, running or not, etc.) whereas a chevy long block (usually low output) go for $300-$500.
    Ya thats exactly what I was planning on with the chevy but oh well, I do have a guy that is willing to trade me my 350 for his olds 350, not sure of the year of that one Im sure its an 80's but at least the car will be running and I don't have have to sink a lot of extra cash into it swapping that all out. So hopefully all will go well, and I will have it going in a week or so.

    I will posting the extra parts on here shortly also, car had a trunk load of extras and I am sure you know how big the trunk is!

  4. #19
    cadillac kevin's Avatar
    cadillac kevin is offline Cadillac Owners Master
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    Re: 81 Coupe DeVille Engine swap

    they didnt make olds 350s in the 80s. just 307s. easy way to tell what year motor it is would be the casting numbers on the heads and the intake. all olds small blocks are the same externally, so you cant tell just by looking at it. 73-80 350s have junk heads. 77-80 motors have weak webbing and are not suitable for performance builds or high rpms.
    this site gives you casting numbers for olds heads
    http://www.442.com/oldsfaq/ofhed.htm#Heads
    and yes I know all about the massive trunk. when I empty it out, the footprint of the junk is about half the length and the width of the car.

  5. #20
    csbuckn is offline Cadillac Owners Connoisseur
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    Re: 81 Coupe DeVille Engine swap

    I would stick with the Chevy 350. For mounts, you just buy some for a 90-92 brougham. You will have to change the exhaust on either motor, thats the expensive part. If you do decide on the Olds 350, I have one sitting in an 88 Brougham that we will be pulling out a the next couple days so I'll have parts for you.

  6. #21
    cadillac_al is online now Cadillac Owners Connoisseur
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    Re: 81 Coupe DeVille Engine swap

    Did you ever verify which frame mounts you have yet?

  7. #22
    asaddman is offline Cadillac Owners Member
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    Re: 81 Coupe DeVille Engine swap

    Quote Originally Posted by cadillac kevin View Post
    easy way to tell what year motor it is would be the casting numbers on the heads and the intake.
    It has an edelbrock aluminum intake on it so I don't know what it is, on the heads are the casting numbers under the valve covers?

  8. #23
    asaddman is offline Cadillac Owners Member
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    Re: 81 Coupe DeVille Engine swap

    Quote Originally Posted by cadillac_al View Post
    Did you ever verify which frame mounts you have yet?

    No I just came to the realization that it still will be easier to put the olds motor in, I will take a couple pics and put them on maybe tonight or tomorrow.

  9. #24
    asaddman is offline Cadillac Owners Member
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    Re: 81 Coupe DeVille Engine swap

    Quote Originally Posted by csbuckn View Post
    I would stick with the Chevy 350. For mounts, you just buy some for a 90-92 brougham. You will have to change the exhaust on either motor, thats the expensive part. If you do decide on the Olds 350, I have one sitting in an 88 Brougham that we will be pulling out a the next couple days so I'll have parts for you.
    I will let you know on the parts, should be ok because I have the old caddy engine and it was complete, also I have to come up with all sorts of parts for the chevy 350, intake, exhaust manifolds, water pump, pulleys not to mention that I need to buy a gasket kit, plus trans and driveline, just too much money out for something that I am not sure if I will keep, and even if I do, I don't need a 300-500 HP motor in that, just something to get me around and run my ac so the wife is happy.

  10. #25
    cadillac kevin's Avatar
    cadillac kevin is offline Cadillac Owners Master
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    Re: 81 Coupe DeVille Engine swap

    look at the link I posted up. it gives you the casting number. its above the center exhaust ports. that'll tell you what it is, along with the ID number or number-letter on the left side of the head (when viewed from the side) those numbers are pretty big and easy to read.

  11. #26
    drmenard is offline Cadillac Owners Enthusiast
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    Re: 81 Coupe DeVille Engine swap

    Get a 77-79 cadillac 425 motor... Its a bolt in... Plenty of power for what you need...

  12. #27
    cadillac_al is online now Cadillac Owners Connoisseur
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    Re: 81 Coupe DeVille Engine swap

    Quote Originally Posted by drmenard View Post
    Get a 77-79 cadillac 425 motor... Its a bolt in... Plenty of power for what you need...
    I'll 2nd that

  13. #28
    asaddman is offline Cadillac Owners Member
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    Re: 81 Coupe DeVille Engine swap

    Quote Originally Posted by cadillac_al View Post
    Did you ever verify which frame mounts you have yet?
    Ok here are the motor mount pics of the 368 in the car, does anyone know if the frame mount will have be changed for the olds 350 or will it sit on this one as long as I have the engine mounted steel perches? this is what I am trying to avoid from having to move the frame mounts and all that, if thats the case I would rather just deal with the chevy 350 because I know it has a ton of power and parts are easier to come by. I am looking for the easiest possible swap that I can find, I have looked for big block caddy motors and haven't had good luck with it here in my area for my price range, plus I would still have to sell the chevy 350 to compensate funds.
    Attached Images

  14. #29
    csbuckn is offline Cadillac Owners Connoisseur
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    Re: 81 Coupe DeVille Engine swap

    The only motor that will bolt to where those frame mounts are is the Caddy motors. 500, 472, 425, 368... All else will have to be moved but did you notice the extra holes in the frame? Those would be where you would move them to. When you take that motor out, I'd be interested in some of the parts. Maybe we can trade if you need some Olds parts. Also, I wanna say the frame mounts are a little smaller than a Chevy or Olds frame mount but I dont remember for sure.

  15. #30
    asaddman is offline Cadillac Owners Member
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    Re: 81 Coupe DeVille Engine swap

    ok that makes sense for sure, the frame mounted mounts should work with the olds 350 though just move the mounts back and make sure the new motor has the brackets still attached? know anyone in GA that has a good running caddy big block? lol that would be the best I guess other than gas being 4.00 a gallon! Well I think I am going to go with the olds 350, been working on two deals, one of them have the olds 350 and trans still bolted together, came out of a cutlass, other one is just the engine, but who knows, would like to have the car running in as little time as possible.

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