Want to transplant from 4.1 to 5.7
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5.0 and 5.7 Discussion, Want to transplant from 4.1 to 5.7 in Cadillac Engine Technical Discussion; Will the motor just drop in? Will i need to get a new trany. Can i use my alternator and ...
  1. #1
    speedrx200 is offline Cadillac Owners Member
    Automobile(s): Fleetwood Limo
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    Want to transplant from 4.1 to 5.7

    Will the motor just drop in? Will i need to get a new trany. Can i use my alternator and power steering, ect... Does anyone know what paper work i would need to do for Colorado state emissions? Anything will help?
    The 4.1 blew a head gasket and everyone that i talk to said get it out of ur car and put a 350.
    thanks for you help

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  3. #2
    creeker is offline Cadillac Owners Connoisseur
    Automobile(s): 1992 eldorado. 2007 dodge magnum hemi r/t
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    Re: Want to transplant from 4.1 to 5.7

    Quote Originally Posted by speedrx200 View Post
    Will the motor just drop in? Will i need to get a new trany. Can i use my alternator and power steering, ect... Does anyone know what paper work i would need to do for Colorado state emissions? Anything will help?
    The 4.1 blew a head gasket and everyone that i talk to said get it out of ur car and put a 350.
    thanks for you help

    You would be going from a tranverse front wheel drive to an inline rear wheel drive engine, not a saturday afternoon job.

  4. #3
    Slacker is offline Cadillac Owners Fanatic
    Automobile(s): 1987 Cadillac Fleetwood Brougham
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    Re: Want to transplant from 4.1 to 5.7

    I did a swap from a HT4100 to an Olds 307. Nothing transferred over from the 4100 for me. Are you looking at an Olds 350 or a Chevy? The HT4100 motor mounts are similar to the the Chevy mounts, I'm not sure they're exactly the same though. (Might save you the trouble of having to drill new mount holes in the frame though...)

    For the tranny, I'm not sure if the trans that came with the HT is a BOP bell housing or chevy. You might be able to get away with a converter plate if it doesn't line up.

    And about the emissions, I don't know about CO but here in NY if you're car is made before '84 you only have to pass safety and there's no emissions. (Upstate might be even more lenient...)

    I don't know how much help my post was, but hopefully it'll start to point you in the right direction.

  5. #4
    sven914's Avatar
    sven914 is offline Cadillac Owners Connoisseur
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    Re: Want to transplant from 4.1 to 5.7

    The 4100 was never used in a limousine. In the '80's, the RWD limos got 368 and 307 (VIN 9) engines, and the 350 was used from 91-96. I don't believe they ever made a FWD limousine (which would have used a 4.5 or 4.9 engine).

    To avoid further confusion; what is the year, model, and 8th digit of the VIN? The first 11 numbers of the VIN would be very helpful.

  6. #5
    80Biarritz is offline Cadillac Owners Member
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    Re: Want to transplant from 4.1 to 5.7

    I have a 4100 Trans in my Eldo, Pushed by a Olds 307. it's a nice combo, but I would love the extra power of a 350. if you are looking at an Olds 350 it will mout to your trans, but you will need all the accessory brackets from the 350.
    Good Luck.

  7. #6
    sven914's Avatar
    sven914 is offline Cadillac Owners Connoisseur
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    Re: Want to transplant from 4.1 to 5.7

    I think we can call this thread dead. Speedrx200 hasn't logged in since 07.22.09 at 1:49pm, which was before the creeker's post.

  8. #7
    ChiPdx84Eldo is offline Cadillac Owners Member
    Automobile(s): 1984 Eldorado Biarritz
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    Re: Want to transplant from 4.1 to 5.7

    If the original poster isn't interested or responsive, I'm happy to get answers or advice on my situation, which is similar.

    I have an 1984 Eldorado Biarritz with the 4100. I got it running and it would idle just fine, but when I took it out on the road, it would overheat very quickly and was making all sorts of bad noises (some lower motor noise convinced me to stop driving it). It has been sitting for about a year now.

    I'm a good mechanic, but am currently about 2300 miles away from the car for work reasons. So here are my questions/thoughts:

    1) is it worth trying to figure out what's wrong with the 4100? I know its gutless and poorly engineered, but I don't want to spend any more time and money than necessary while I'm away from the car.

    2) I remember the guy who ran Eldo Country posting some great how-tos, but his old website and his radar58 website are both down now. Any ideas how to find that information? ie. what motors, what parts need to be saved, etc.

    3) Can anyone give me a rough idea of what it should cost for a mechanic to do this repair? It can be in terms of hours rather than dollars. If I can, I'll wait to do the job myself, but I likely won't be able to get to it for at least 6 mos. and I hate for the car to just sit there.

    Thanks for your answers and advice - I can promise I'm happy to provide any other info that you need to answer my questions. I'm trying to make a decision about this car in the next week or so and I need to be mentally ready if it's going to the scrapyard or craigslist.

    Thanks again,

    Devin

  9. #8
    sven914's Avatar
    sven914 is offline Cadillac Owners Connoisseur
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    Re: Want to transplant from 4.1 to 5.7

    I don't have much experience with the 4100, but just from talking to some of the people on the forums, I have gotten that when those engines start to go, they're gone. Some people refer to that lower engine noise as "the 4100 death rattle," because it is basically an indication of the lower end of the engine coming apart. At this point, the engine needs to be rebuilt, and have allot of new parts installed, which is going to be very costly.

    If it were my car, I would get a junkyard Oldsmobile 307. The 307 is interchangeable with the transmission used for the 4100, and will mount as a FWD engine. The 307 would have to be taken apart and inspected, but it should not require the amount of parts the 4100 would need. Being that the 307 would not require a complete rebuild, it would also take less time and labor cost to install. The downside to the 307 is that it is carburetted and will decrease your fuel efficiency, and it will not work with the trip computer (if you have one).

  10. #9
    cadiman76 is offline Cadillac Owners Member
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    Re: Want to transplant from 4.1 to 5.7

    Quote Originally Posted by 80Biarritz View Post
    I have a 4100 Trans in my Eldo, Pushed by a Olds 307. it's a nice combo, but I would love the extra power of a 350. if you are looking at an Olds 350 it will mout to your trans, but you will need all the accessory brackets from the 350.
    Good Luck.
    Could you give me some info on procedere for this swap i am considering the same thanks Peter

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