4.9 instead of 4.5??
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HT4100 4.1, 4.5, 4.9 Discussion, 4.9 instead of 4.5?? in Cadillac Engine Technical Discussion; hi ...just wondering if it is a good idea or possible to swap a 4.9 for a 4.5?? and would ...
  1. #1
    Yagos is offline Cadillac Owners Member
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    4.9 instead of 4.5??

    hi ...just wondering if it is a good idea or possible to swap a 4.9 for a 4.5??
    and would it be worth it?
    for a 88 fleetwood

    open to thoughts or suggestions

    Thanks

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    Edahall's Avatar
    Edahall is offline Cadillac Owners Enthusiast
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    Re: 4.9 instead of 4.5??

    Yes, it's possible to that swap. You'll need to use an adjustable Fuel Pressure Regulator (FPR) to dial in the correct fuel requirements for the larger displacement engine. Use the intake manifold and TBI from your 4.5. Hope this helps.

  4. #3
    awadecki is offline Cadillac Owners Enthusiast
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    Re: 4.9 instead of 4.5??

    I don't think it'll work that well...probably won't be able to get enough fuel with that 4.5 TBI. Also, the 4.9 uses an electronically controlled transmission, and the computer will wonder what's going on without it. You could, however, swap a 1990 4.5 PFI (180hp vs. 155) without much trouble I believe as long as you change the ECMs.

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    Edahall's Avatar
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    Re: 4.9 instead of 4.5??

    The 4.5 TBI can supply enough fuel if an adjustable FPR is used. Keep the 4.5 electronics as well as the original 440T4 non-electronic transmission.

    One of the members has done this exact conversion sucessfully. Hope he chimes in on this topic.

  6. #5
    Yagos is offline Cadillac Owners Member
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    Re: 4.9 instead of 4.5??

    hmmm, ok
    i wont be doing this until funds allow but i might as well get started on the research.
    Thanks for the input

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    Edahall's Avatar
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    Re: 4.9 instead of 4.5??

    Funds??? It should not be a costly conversion. Check out the wrecking yards in your local area. A wrecking yard near my area will sell me a 4.9 for $80. If the engine has less than 150k miles, I would not bother to rebuild it. These are very long lasting engines. If more than 150k miles, I might replace the piston rings. The other thing to note is whether or not the 4.9 heads will adapt to the 4.5 intake manifold that you would use. I believe that it works with some modifications to get the water ports to line up. I can look this up for you if you would like. Send me a Private Message if you're interested and I'll also forward you a article that explains all the differences between the heads and intake manifolds. The other expense would be the adjustable FPR which is not expensive. But the most expense will be time and labor.

    By the way, what is wrong with your 4.5? My 88 eldorado also has this engine and at 240k miles and it still chugs along fine. I waiting for it to bite the dust so I can also do the 4.9 conversion but I bet it'll get 300k before it needs attention. It would be neat to have a 4.9 with TBI in this car because the TBI system is so much simpler. I only have to worry about 2 injectors that rarely clogs up rather than 8. Also, my car has the rare astroroof and I have also installed the touring suspension which includes sway bars and a fast ratio steering rack. The pearl blue custom paint job makes it a sweet ride.

    Your 88 Fleetwood would be a good candidate for the 4.9 since the newer Fleetwoods got much larger. The styling on the 87/88 FWD Devilles/Fleetwoods is also very sweet.

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    illumina's Avatar
    illumina is offline Cadillac Owners Connoisseur
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    Re: 4.9 instead of 4.5??

    Quote Originally Posted by Edahall View Post
    The 4.5 TBI can supply enough fuel if an adjustable FPR is used. Keep the 4.5 electronics as well as the original 440T4 non-electronic transmission.

    One of the members has done this exact conversion sucessfully. Hope he chimes in on this topic.

    I refuse to chime any further...

    I swapped a 4.1 with a 4.5 and used an adjustable FPR, dialed about 10% higher than stock values for the 4.1 liter. The same can be done with the 4.5 to 4.9 swap, so as long as you're still running TBI. Otherwise, you're going to run into some problems.

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    Yagos is offline Cadillac Owners Member
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    Re: 4.9 instead of 4.5??

    Hopefully it is as easy as you guys make it sound
    There is nothing wrong with my 4.5 it has 167k kilometers don't know off hand what that is in miles.
    Thanks for the help guys.

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    Yagos is offline Cadillac Owners Member
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    Re: 4.9 instead of 4.5??

    .....not enough posts to PM yet, guess i have to talk more

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    Yagos is offline Cadillac Owners Member
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    Question Re: 4.9 instead of 4.5??

    Another question....
    Would there be a certain year of the 4.9 recommended or would it not matter at all??

    Thanks

  12. #11
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    HUF
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    Re: 4.9 instead of 4.5??

    Quote Originally Posted by Yagos View Post
    Another question....
    Would there be a certain year of the 4.9 recommended or would it not matter at all??

    Thanks
    The 4.9s are known to have that #1 main bearing thump/knock. As far as I remember GM made changes to eliminate the prblem after the first year of production (which is 1991). But looks like later models have the same problem.

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    ROGER L's Avatar
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    Re: 4.9 instead of 4.5??

    Quote Originally Posted by Yagos View Post
    hi ...just wondering if it is a good idea or possible to swap a 4.9 for a 4.5??
    and would it be worth it?
    for a 88 fleetwood

    open to thoughts or suggestions

    Thanks
    I HAD A 1993 Seville 4.9L for 5 1/2 years and it had 188K when i got it and 266K when a hse blew on it my friend tried to fix it then he had a guy look at it and they both fixed it together that car i bought new trans at 210K, then new trans cooler lines new water pump, struts were broke for 2 1/2 years never a radiator problem over heated once in the wisconsin dells on a vacation but it had too much water in the system i found ouy later on

  14. #13
    derrty_deville's Avatar
    derrty_deville is offline Cadillac Owners Enthusiast
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    Re: 4.9 instead of 4.5??

    Quote Originally Posted by Yagos View Post
    Hopefully it is as easy as you guys make it sound
    There is nothing wrong with my 4.5 it has 167k kilometers don't know off hand what that is in miles.
    Thanks for the help guys.
    Why bother then with it if it works fine and has such low mileage. Maintain it and enjoy it. The 4.9 is better but not really worth swaping out IMO.

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