What motors will fit my caddy
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5.0 and 5.7 Discussion, What motors will fit my caddy in Cadillac Engine Technical Discussion; What motors will fit a 1986 fleetwood brougham? i have the 140 hp 307-y. What all will i have to ...
  1. #1
    86FLEETWOOD is offline Cadillac Owners Member
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    Post What motors will fit my caddy

    What motors will fit a 1986 fleetwood brougham? i have the 140 hp 307-y. What all will i have to change if i replaced my 307

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  3. #2
    sven914 is offline Cadillac Owners Connoisseur
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    Re: What motors will fit my caddy

    You can down grade into the less powerful, but more fuel efficient HT4100 (82-85 RWD's) and still keep your transmission. You would have to get the electronic hardware off the 4100 car because you will be going from carburetted to fuel injected.

    You could go into a 368 (80) (had the V8-6-4 function for 1981) and will have to change the transmission. The 368 will only bolt up to a 3-speed.

    You could also go into a Buick 250 Six Cylinder (80-84)and would have to change transmission.

    Another option is the Chevrolet 305 (91-92), which would give you the same benefits as the 307. It has TBI so you would need the computer to control it and a new transmission.

    The most popular change is to the Chevrolet 350 (L05 90-93/LT1 94-96). The L05 350 engine used by Cadillac was TBI, but you can get a carburetted one from an 80's Caprice. It would probably the easiest conversion, to go to a 350 with a non computer controlled carburettor and remove your computer from the system. The 350 too will require a different transmission.

    Whenever you are upgrading in engine power, you need to change the rear axle ratio. Also the engine/transmission mounts may be different for the different engines.

  4. #3
    86FLEETWOOD is offline Cadillac Owners Member
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    Cool Re: What motors will fit my caddy

    Thank you for the information. My current engine is 307 vin y. I read that i can rebuild it as the 307 vin 9 which has more horsepower. would i be able to use use the same computer? i will have to change the rear axel ratio also as well, right?

  5. #4
    sven914 is offline Cadillac Owners Connoisseur
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    Re: What motors will fit my caddy

    I don't believe you need to change the rear end if you do that (I think the stock one was built to accommodate the extra horse power). But if it concerns you, then it wouldn't hurt to install the final drive from an 88+ (with a 5.0 engine), which has a larger ratio.

    To modify the "Y" engine, you need a performance cam, stiffer valve springs, a larger vibration dampener, and a high flow carburetor. "9's" also came with duel outlet exhaust, so you can get a new exhaust system installed. Being that the "9" still used a feed back carburettor, you may need to change the computer (otherwise it may starve the engine and throw rich codes).

  6. #5
    86FLEETWOOD is offline Cadillac Owners Member
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    Re: What motors will fit my caddy

    Thanks alot, you really know your caddys

  7. #6
    brougham is offline Cadillac Owners Master
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    Re: What motors will fit my caddy

    Unless you want to change a lot of parts you'd be better off staying with an oldsmobile engine.

  8. #7
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    RocketFast321 is offline Cadillac Owners Fanatic
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    Re: What motors will fit my caddy

    Stay with olds. Since you have a olds 307, you can put a olds 350 in. Just swap everything off your 307 to your olds 350. Intake and all 50' of vacuum lines.

  9. #8
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    Aron9000 is online now Cadillac Owners Master
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    Re: What motors will fit my caddy

    I'd look for some performance cylinder heads, intake, headers, true dual exhaust along with a mild cam if you are going to do an Olds 350 build. Might as well do it right if you're going to swap the motor. That would be a fun combo with at least 300 crank hp.

  10. #9
    N0DIH's Avatar
    N0DIH is offline Cadillac Owners Master
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    Re: What motors will fit my caddy

    If it was me? Go spend $800 on a used 5.3L LM7 out of a newer GMC/Chevy truck. Get the trans too. It is a bigger swap, but you will LOVE it.

    Why use old engines that struggles to get to 300 hp when a 5.3L is 300+ out of the box.

    If fuel economy is more important, a 4.8L is a bit better, but being they make less of them, probably more expensive.

    If power is the game, then get a 6.0L LQ4 or LQ9.

    Yes, these are a bigger project, but if you are wanting a modern high fuel efficient engine that will keep your Cadillac living on forever, this is the investment I would seriously look into.

    Car-part.com and look up a 50K mile engine or so, you will be surprised how inexpensive they are compared to doing something like an LT1 or L05 or an Olds 350 swap. Not as easy, but far more rewarding.

  11. #10
    86FLEETWOOD is offline Cadillac Owners Member
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    Re: What motors will fit my caddy

    What else would i have to chage w/ that motor swap.

  12. #11
    N0DIH's Avatar
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    Re: What motors will fit my caddy

    With Gen III or Gen IV Engines, would be fun.

    What I DO know is the oil pan will need mods (and don't start with a Corvette oil pan), use truck manifolds (they appear to be closest to fit), you will need custom engine mounts, but by now they might be available from someone.

    You will need to mod it for EFI, so you will need the pcm a to be able to tune it (I can do, so for me not an issue). So no carbie anymore. So you will need a high pressure fuel pump in the tank, you have to hunt around to find radiator hoses and heater hoses that will match up.

    It isn't the simple projo like a 350 Olds swap which is very very simple (Did that one on my 85 Cutlass). But the rewards are great, but the work is much more. Imagine having brand new car drivability and fuel economy like mid 20's highway and high teens city. And have power that would be phenomenal for a big car.

  13. #12
    N0DIH's Avatar
    N0DIH is offline Cadillac Owners Master
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    Re: What motors will fit my caddy


  14. #13
    sven914 is offline Cadillac Owners Connoisseur
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    Re: What motors will fit my caddy

    If your going to go through all that trouble; why not drop in a Cadillac 500? at least that would save you the electronic headaches.

    Theoretically the 500 should fit fine. The 80-81 Cadillac RWDs (with you body style) had the 368 engine. The 368 was a 77-79 425 block, re-bored for economy. The 425 was based on the 472's block, 68-74. The 472 was an undersized version the 500, used from 1970 to 1976. The 500 is the world's largest and most powerful (400hp for 1970) gasoline motor, ever offered in a passenger vehicle.

    Why waste you time with a new engine that struggles to make 295hp (Chevrolet 1500 series specification for the 5.3).

  15. #14
    N0DIH's Avatar
    N0DIH is offline Cadillac Owners Master
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    Re: What motors will fit my caddy

    It has 295 hp is weakest form (first year) or so, got up to 315hp. It makes this power with a tiny cam, and you will NEVER get 25+ mph on a 500 Caddy no matter what you do.

    All depends on what you want. Power and Economy, the Gen III/IV GM engines. Power, old school gas guzzling V8's. Sure, you can do well with a 500, but in this economy, you are going to going to spend around the same amount of $, might as well get something that rocks on mpg and runs great has AWESOME driveability and ability to make 400 hp very easily and still knock down great mpg. The 500 will just never do it.

    Honestly, I have given up on "old school" engines for the modern economy and power.

    Look at the engines like this.

    The Olds 307 never made over 180 hp in HO form, 140 hp in std form. Cam in the 180 duration range.
    The L05 305 Chevy made 210 hp.
    The L99 (the 265 CID LT1) makes 200 hp with fast burn heads, reverse cooling and 10:1 compression.
    The LT1 5.7L makes 260 hp with fast burn iron heads and same cam as above (195 or so intake duration)
    The LT1 5.7L Corvette/Firebird/Camaro engine makes 285-300 hp with 10.75:1 comp alum heads, and a bigger cam, (202 intake duration/207 exhaust)
    The LT4 5.7L Corvette engine makes 345 hp (considered underrated to not overshadow the LS1) with a 203 intake / 210 exhaust duration cam.
    The LS1 5.7L makes (in 2004) 350 hp and 365 lb/ft torque with a 197/207 duration cam. The LS1 and LM7 (5.3L) are virtually same engine, LS1 having bigger bore.
    The LM7 5.3 Vortec truck engine is 285 hp with a 190/191, 0.466" / 0.457" on a 114 LSA cam. That is one small cam to make that sort of power with only 5.3L.

    So lets take a 76 500 Cadillac, with around the cam cam specs as a LS1, made a pathetic 200 hp. And the LS1 made 350 hp.

    $ for $, take a LS1 and you take a 500 and I will make 500 hp easier and cheaper. And have much better fuel economy and drivability. The amount of work to build a 500 up would be very expensive. You are talking an engine that had its last update in 1983 or so. The LS1 engines are new from the ground up.

    To each his own, I would keep my options open. More work to put in newer engine, but far more efficiency and better emissions. But it isn't a no brainer drop in swap. A Cad 500 would be a fairly easy swap in comparison.

  16. #15
    sven914 is offline Cadillac Owners Connoisseur
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    Re: What motors will fit my caddy

    Quote Originally Posted by N0DIH View Post
    So lets take a 76 500 Cadillac, with around the cam cam specs as a LS1, made a pathetic 200 hp. And the LS1 made 350 hp.



    To each his own, I would keep my options open. More work to put in newer engine, but far more efficiency and better emissions. But it isn't a no brainer drop in swap. A Cad 500 would be a fairly easy swap in comparison.
    I though about it a little longer and my theory about the 500 fitting in fine wasn't exactly correct. The largest engine that could go in to your car, without any modification to the dimensions of the engine compartment is a 425. The 472 and 500 are big block motors, so you will have to increase the size of the engine compartment to make the fit. I don't know by how much and what, if anything, you would have to sacrifice to make the fit.

    Someone on the RWD forum asked about putting a 500 in a 90 Brougham; the discussion might be useful.

    As for the 76 only being able to make a pathetic 200 horsepower; to meet emission and fuel mileage requirements, Cadillac was forced to reduce the compression. 500's after 70 were also equipped with a smog pump, which killed their power. 1970 was the only year they made 400hp.

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