How much would it cost to put a big block engine in an 85 Eldorado?
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The Classic Cadillac Forum Discussion, How much would it cost to put a big block engine in an 85 Eldorado? in Past Cadillac Vehicle Discussion; I've ran in to some money and am curious how much it would cost to put a big block in ...
  1. #1
    TheChicagoan is offline Cadillac Owners Member
    Automobile(s): 1985 Eldorado
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    How much would it cost to put a big block engine in an 85 Eldorado?

    I've ran in to some money and am curious how much it would cost to put a big block in a 85 Eldorado. This car is notable as a never ending money pit and I want to once and for all make it reliable and add some much needed performance. Has anyone on Cadillac Forums ever done a full restoration or nice engine swap with an 85? How much would it cost to completely rip out the 4.1 and replace it with a big block of some sort? I want to do something similar to what Count's Customs does on the History Channel.

    Thanks,

    TheChicagoan

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  3. #2
    carnut is offline Cadillac Owners Master
    Automobile(s): 1988 Allante' (sold), 1984 Eldorado, 84 Sedan DeVille
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    Re: How much would it cost to put a big block engine in an 85 Eldorado?

    The problem with this is the transmission is only strong enough for 250 cubic inches! so a gas Toronado transmission is needed as well. A 403 big block Olds will bolt in with a Toronado Diesel or gas oil pan and oil pump pick up. It would require a larger radiator core and all the bracketry from the donor engine. I've read of many 350 Olds engines fitted to this chassis and the 403 is just a little taller.

  4. #3
    amunderdog is offline Cadillac Owners Connoisseur
    Automobile(s): 1994 SLS x 2 ---- 1993 Eldorado Sport ----- 1994 Deville 4.9
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    Re: How much would it cost to put a big block engine in an 85 Eldorado?

    Usually?
    Start by acquiring a donor vehicle.
    big block swaps are usually very difficult.
    There are plenty of stout small blocks around that would be much easier all the way around.

  5. #4
    carnut is offline Cadillac Owners Master
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    Re: How much would it cost to put a big block engine in an 85 Eldorado?

    Keep in mind the transmission is a BOP (Buick, Olds, Pontiac) bolt pattern to the rear of whatever engine you might choose.

  6. #5
    aeronca36606 is online now Cadillac Owners Enthusiast
    Automobile(s): 85 Coupe Deville 4.1 V8 & 4.3 V6 Deisel & 1970 Eldorado
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    Re: How much would it cost to put a big block engine in an 85 Eldorado?

    The V8-6-4 used in the eldorado is obviously a bolt in. It is also part of the 472/500 family of engines. Either of these 2 engines would probably leave the transmission internals in small pieces the first time you floored it! The 368/V8-6-4 is a good engine and will run as a v8 with a small wiring modification. These engines are almost always good in the wrecking yards as they are a tough unit. This said you will have some trouble interfacing the engines electronics into your 85 but it can be done.

  7. #6
    Bro-Ham's Avatar
    Bro-Ham is offline Cadillac Owners Connoisseur
    Automobile(s): 1979 Cadillac Sedan deVille d'Elegance
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    The 79 and 80 (and 81 with the problematic V8-6-4) had the delicious larger engines you crave. Get a 1980 Eldo with a 6.0 368 as a donor, put on a carb, and I would think you're in business! Sooop it up per MTS and then it is over the top! A 1985 Eldo deserves that! Good luck!

  8. #7
    70eldo's Avatar
    70eldo is online now Cadillac Owners Connoisseur
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    Re: How much would it cost to put a big block engine in an 85 Eldorado?

    With the big block I would worry about the space under the hood as that engine would be on top of the TH400 transmission (which you will need due to the torque). I think the other suggestions placed above with smaller engines would serve you better.

  9. #8
    TheChicagoan is offline Cadillac Owners Member
    Automobile(s): 1985 Eldorado
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    Re: How much would it cost to put a big block engine in an 85 Eldorado?

    Thanks for the input guys. If I were to order a 350 Olds motor for the 85, what year and can I hop it up without blowing my transmission? And how many horses will I get? Also I'm looking for an engine that can produce at least 300 horses.

    Thanks,

    TheChicagoan

  10. #9
    cadillac kevin's Avatar
    cadillac kevin is offline Cadillac Owners Master
    Automobile(s): chevy 350 powered 86 FWB, 00 safari h.t. 66 toro, 83 lesabre
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    Quote Originally Posted by TheChicagoan View Post
    Thanks for the input guys. If I were to order a 350 Olds motor for the 85, what year and can I hop it up without blowing my transmission? And how many horses will I get? Also I'm looking for an engine that can produce at least 300 horses.

    Thanks,

    TheChicagoan
    Get a 70-73 (hardened valve seats). It will make maybe 250 hp (even though they were rated at 300+ hp) with all the accessories (remember, the old way of rating engines was with no accessories and under optimal conditions). Your 200r4 (or what ever they called it in fwd form) can handle 330 ft/ lbs of torque, which will be about what that engine puts out.

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