Please dont be angry with this question!
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500, 472, 425, 368 Discussion, Please dont be angry with this question! in Cadillac Engine Technical Discussion; ...
  1. #1
    Captain wow's Avatar
    Captain wow is offline Cadillac Owners Member
    Automobile(s): 1970 Eldorado (prev:78Eldo-73Eldo-79CDV-78Sev-79Sev)
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    Red face Please dont be angry with this question!

    Hi, i live in england...my daily driver is a 1970 500ci fwd eldorado,
    It currently gets around 7mpg in town (havent taken it on higway yet as its waiting for new front end rubbers)

    I had planned to add an LPG (liquid petroleum gas) conversion to save money on fuel bills. Lpg is approx half the price of petrol so that would make my eldo the equivalent of 14 mpg in town....in my opinion thats better but still outrageously expensive in the uk-(petrol is aprox £1.10 and lpg is approx £0.60 sterling). My ideal target would be 20 in town 30 on highway... Yeah i know!!

    Here is my crazy question...
    Has anyone ever swapped the 8.2 V8 for a smaller/better fuel economy engine...maybe another more modern caddy block or even a diesel truck engine? This is a huge hypothetical question but i am serious in keeping this car and using it every day i'd sleep in it if my wife wouldnt mind! If it were doable i would want to keep the original engine nice and safe in storage just in case...some of you MUST have considered this.

    There..ive said it!

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  3. #2
    donwon is offline Cadillac Owners Enthusiast
    Automobile(s): 92 Deville
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    Re: Please dont be angry with this question!

    If you can get in touch with Jay Leno ask about what he did to an Olds. Toronada.
    Anything is possable if you have the money.
    Right off hand I don't know what other engine would fit. Possably a 4.3L v6 but it might not pull that big of a car.

  4. #3
    johnny kannapo's Avatar
    johnny kannapo is offline Cadillac Owners Connoisseur
    Automobile(s): 1996 Eldorado
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    Re: Please dont be angry with this question!

    Jay Leno has no problem putting $250,000in a car. I owned Toro's before and they are very very close to being the same, Toro engine, transaxle, are the same basic set up and Olds mass produced big blocks that were well built smooth running, powerful, durable, very dependable. The Toronado engine is the same except for these differences; but bolt right up. The intake manifold is lower profile to accommodate the engine sitting higher in the engine bay, the exhaust manifolds, the oil pan and possibally the frame mounts. I think all these parts will interchange with rear wheel drive engines, bolt right up..as well as long as the engine family is the same. The Toro had a 400ci, 425ci, and a 455ci, Post 1971 engines had lowered compression. I know England may offer little in early 70's Olds parts. I would look for a post 1972 engines both a 455Toroanado, and a 400ci rear drive car. Parts are all availiable. 72' cars and later had 8.5 to 1 compression& hardend valve seats and better valve materials. You could reduce the cubic inches by 100. Look into this. the gm cars had many simularities and many components that interchange.

  5. #4
    BRUCE ROE is offline Cadillac Owners Fanatic
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    Re: Please dont be angry with this question!

    First check your final drive ratio. If its a 3.07, a 2.73:1 would save some gas. You could also put in a reversed POWER DRIVE, which is a 65:57 ratio transmission chain set. That would get your overall final ratio to 2.40. POWER DRIVEs are used in GMC motorhomes, which share the same drive train as FWD 66-78 Toro & Eldo. The GMC people have done all kinds of work on these things, including fuel injection and diesel conversion. The engine advice was good; an Olds 403 would help with some loss of performance. These small blocks were used in 77-78 Toro; however an easier conversion would be to a Cad 77-78 425 engine which bolts directly in. A 350 Olds would start to be rather sluggish, and the 350 Olds based diesel would also fit. But these diesels have an awful reputation and would really be slow. If you do get down to a 300 or less engine (a 3.8L V6 can be made to fit) AND get the 2.40 overall ratio, you can get back a some of the lost performance with a 66/67 TORO SWITCH PITCH version of your transmission. You can see a (downsized) 79 Eldo with 67 switch pitch trans, fuel injected 403, and power drive (2.40 overall ratio) on PHOTOBUCKET. This setup has plenty of tire spinning power; it would be slower in a car your size. Bruce Roe CLC # 14630

    http://s93.photobucket.com/albums/l71/bcroe/

    (that is a lower case "L"71, not an upper case "i"71)

    click on an Album a left
    click on a picture to enlarge, or
    click on "view as a slide show"

  6. #5
    Captain wow's Avatar
    Captain wow is offline Cadillac Owners Member
    Automobile(s): 1970 Eldorado (prev:78Eldo-73Eldo-79CDV-78Sev-79Sev)
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    Re: Please dont be angry with this question!

    Holy cow! i didnt expect anyone to take this so seriously...Thanks guys. i dont know much about swapping engines..well actually i know nothing, my instinct is that the easiest would be to go for the 77-78 eldo engine as suggested by bruce roe but ive just recently sold my 78 eldo cos it felt weak as hell and i prefer the shape of the 68-70. . However i managed to get 27mpg on the highway and 13mpg in town from its 7litre.

    I just had a look at modern cadillac economy and im amazed that they arent that much better! on average its reported they get 17/22 mpg- coupes, sedans and suvs!

    Bruce-I dont know about final drive ratio..i'll check that out.
    I wonder if Jay Leno wants to invest in a charity project!?

    Most definitly though if this swap were to go ahead it would have to be a huge improvement to be worth the butchering and trouble.

  7. #6
    steelybill is offline Cadillac Owners Enthusiast
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    Re: Please dont be angry with this question!

    The bolt pattern on that transaxle should be the usual BOP
    Buick/Olds/Pontiac, and Cadillac. A 350 Olds or Pontiac may fit, or even a 350 Buick engine. A V6 wouldn't be a good idea for that big car. The '76 Coupe Deville I had weighed 5300 lbs, and yours is likely up there too.

  8. #7
    BRUCE ROE is offline Cadillac Owners Fanatic
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    Re: Please dont be angry with this question!

    A Toronado oil pan will help put any Olds in the car. But you will end up making a custom pan for a Buick, etc. Again a 368 Cad engine would be easier. I'm not sure your A/C compressor setup will fit anything but a 68-79 Cad engine. Bruce Roe CLC # 14630

  9. #8
    awadecki is offline Cadillac Owners Enthusiast
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    Re: Please dont be angry with this question!

    i have 2 1976 eldorados and i get about 16mpg freeway and 10mpg around town in the cold weather, running 11 degrees base timing advance (vs. stock 6 degrees) with a plugged egr port (no spark knock when running on midgrade), a rebuilt carburetor, and complete tune up.

    you should be able to get about the same. while increasing your mileage from 7mpg to 10mpg doesn't sound like much, that's a 40% decrease in fuel consumption! my suggestion is to try rebuilding the carb before you do anything else. if you have to crank your car for a while after it rests for about 20-30 mins for it to start, your well plugs in the carb are leaking and that's just lost fuel. epoxy them so that they don't leak and your car will start instantly when warm (just a flick of the wrist), and you won't be dumping too much fuel in at idle, hurting your in-town fuel economy.

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