Cadillac Deville 74 472, increasing engine compression
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500, 472, 425, 368 Discussion, Cadillac Deville 74 472, increasing engine compression in Cadillac Engine Technical Discussion; HI Everbody! I actually own a Cadillac Sedan Deville with the V8 472 Cu, it only has 39000 original and ...
  1. #1
    josehf34 is offline Cadillac Owners Member
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    Cadillac Deville 74 472, increasing engine compression

    HI Everbody!

    I actually own a Cadillac Sedan Deville with the V8 472 Cu, it only has 39000 original and documented miles, he rides like a dream but I don't know how much MPG is actually doing but i think is lower than 9 MPG. So this is my question:

    I Want to install on it an edelbrok or holley EFI System and increase the engine compression to 13:1 or 14:1 (or 15:1 if is possible) to use it only in homemade ethanol (cheaper and cleaner than gasoline), is possible to do this? How much MPG can I expect to get doing this?

    I can be happy with 12 - 13 MPG on city to use this like my semi - daily driver

    Thank you everybody

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  3. #2
    steelybill is offline Cadillac Owners Enthusiast
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    Re: Cadillac Deville 74 472, increasing engine compression

    The '74 472 has flat top pistons from what info I have, as opposed to the various shaped dished pistons in other years. They are listed as having 8.2 to 1 compression ratio, which is lower than most. The '74 has the large chamber heads ( 120 CC), while earlier engines had the small chamber heads .There's folks who know much more than I do. This forum will not let me give you the address to that forum. A parts supplier for the big Caddy engines is MTS.

  4. #3
    BRUCE ROE is offline Cadillac Owners Fanatic
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    Re: Cadillac Deville 74 472, increasing engine compression

    Before you spend a fortune on high compression, has the engine been brought up
    to new standards? Does it have a replacement timing chain, a new Cat Converter
    or even none at all? Is the ignition advance working exactly right?

    To get better mileage, I'd start with bringing all maintenance up to date (including
    above). Check the axle ratio, a 2.41:1 is good. Consider using an overdrive trans
    with lockup converter, a 4L80E will do a lot more than a compression increase.
    An electronic spark advance will do more for you than fuel injection without spark
    control. Bruce Roe

  5. #4
    josehf34 is offline Cadillac Owners Member
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    Re: Cadillac Deville 74 472, increasing engine compression

    Thank you for the responde.

    If I unsertand you I think will be necessary to change the pistons. Are this right?

    I think if I raise up the compression ratio to 13:1 or 14:1 I can get a nice extra power and do a better MPG on my caddy

  6. #5
    BRUCE ROE is offline Cadillac Owners Fanatic
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    Re: Cadillac Deville 74 472, increasing engine compression

    Before you spend a fortune on high compression, has the engine been brought up
    to new standards? Does it have a replacement timing chain, a new Cat Converter
    or even none at all? Is the ignition advance working exactly right?

    To get better mileage, I'd start with bringing all maintenance up to date (including
    above). Check the axle ratio, a 2.41:1 is good. Consider using an overdrive trans
    with lockup converter, a 4L80E will do a lot more than a compression increase.
    An electronic spark advance will do more for you than fuel injection without spark
    control. Bruce Roe

  7. #6
    josehf34 is offline Cadillac Owners Member
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    Re: Cadillac Deville 74 472, increasing engine compression

    Quote Originally Posted by BRUCE ROE View Post
    Before you spend a fortune on high compression, has the engine been brought up
    to new standards? Does it have a replacement timing chain, a new Cat Converter
    or even none at all? Is the ignition advance working exactly right?

    To get better mileage, I'd start with bringing all maintenance up to date (including
    above). Check the axle ratio, a 2.41:1 is good. Consider using an overdrive trans
    with lockup converter, a 4L80E will do a lot more than a compression increase.
    An electronic spark advance will do more for you than fuel injection without spark
    control. Bruce Roe
    A four speed transmission on this heavier Cadillac? I thought was impossible to use this kind of transmission on this car because the lots of torque from the 472 and the weight of the car will to destroy it, how much MPG can I Expect to get with a transmission like this and changing the axle ratio?

    About the ignition system I want to buy an MSD kit to install on the caddy.

    I've a doubt: What electronic spark advance do you recommend? I was searching and I find that exists static electronics spark advance and programmable spark advance and Can I still using the stock gear selector if i install the 4L80E?

  8. #7
    Roadmaster75's Avatar
    Roadmaster75 is offline Cadillac Owners Member
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    Re: Cadillac Deville 74 472, increasing engine compression

    Before you embark on tranny swaps and major engine work...start with
    a complete MSD ignition system including their coil, spark plug wires, etc.
    Check the mileage once it's all in and advance is optimized
    THEN
    have a known Quadra Jet expert rebuild and recalibrate your original Quadra Jet
    for todays fuel... and make sure he knows everything about your car ...weight, axle ratio,
    engine specs,etc.
    You might be surprised by the performance & mileage improvements as you dial these two factors in...
    (you may even consider a chassis dyno session to get to your optimum settings done all at once.)

    If you decide to go deeper ...at least you'll have the ignition covered and the carburetor covered

  9. #8
    josehf34 is offline Cadillac Owners Member
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    Re: Cadillac Deville 74 472, increasing engine compression

    Quote Originally Posted by Roadmaster75 View Post
    Before you embark on tranny swaps and major engine work...start with
    a complete MSD ignition system including their coil, spark plug wires, etc.
    Check the mileage once it's all in and advance is optimized
    THEN
    have a known Quadra Jet expert rebuild and recalibrate your original Quadra Jet
    for todays fuel... and make surehe knows everything about your car ...weight, axle ratio,
    engine specs,etc.
    You might be surprised by the performance & mileage improvements as you dial these two factors in...
    (you may even consider a chassis dyno session to get to your optimum settings done all at once.)

    If you decide to go deeper ...at least you'll have the ignition covered and the carburetor covered
    I have a problem with the underlined text, I'm from south america and there's no much cadillacs like this, I know experts in General Motors engines and cars (Chevrolet, Buick, Pontiac) but I don't know if they know everything about this cadillacs.

    I guess you did what you're recommending to me so what's your cadillac engine and city and highway MPG?

    About the MSD System, must I use a specific reference for this engine or any system can be used with the same results? (This question is because I see a lot of systems made for Chevy Big Blocks)

  10. #9
    drmenard is offline Cadillac Owners Enthusiast
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    Re: Cadillac Deville 74 472, increasing engine compression

    If you want high compression to use a different fuel that can be done by changing your large chamber heads to small chamber heads...The small chamber heads were used from 1968 to 1973.. The large chamber were used from 1974 to 1976.. I am not sure about valve clearance when changing heads .. pistons may have to be cut for clearance.. If you do this you must know of all other things that must be done to make it run...Changing the heads will give you about 12 to 1 or a little more compression...

  11. #10
    BRUCE ROE is offline Cadillac Owners Fanatic
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    Re: Cadillac Deville 74 472, increasing engine compression

    Quote Originally Posted by josehf34 View Post
    A four speed transmission on this heavier Cadillac? I thought was impossible to use this kind of transmission on this car because the lots of torque from the 472 and the weight of the car will to destroy it, how much MPG can I Expect to get with a transmission like this and changing the axle ratio?

    About the ignition system I want to buy an MSD kit to install on the caddy.

    I've a doubt: What electronic spark advance do you recommend? I was searching and I find that exists static electronics spark advance and programmable spark advance and Can I still using the stock gear selector if i install the 4L80E?
    A 200R4 trans isn't strong enough for a 472 engine, but a 4L80E is just as strong as the original
    TH400. Set the rear axle ratio to put you at 1500 rpm at 60 mph in overdrive, converter locked.
    Might get 2 mpg over any other problems you correct. Selector will take some adjustment; so will
    any 4 speed. Parts for the conversion are on the market. A compression of 14:1 isn't streetable
    for gasoline fuel, might work on propane or E85.

    The greatest advantage of fuel injection on old engines is controlling emissions, it won't help
    mileage much. Good accurate spark will do more, perhaps with knock detector. Bruce Roe

  12. #11
    josehf34 is offline Cadillac Owners Member
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    Re: Cadillac Deville 74 472, increasing engine compression

    Quote Originally Posted by BRUCE ROE View Post
    A 200R4 trans isn't strong enough for a 472 engine, but a 4L80E is just as strong as the original
    TH400. Set the rear axle ratio to put you at 1500 rpm at 60 mph in overdrive, converter locked.
    Might get 2 mpg over any other problems you correct. Selector will take some adjustment; so will
    any 4 speed. Parts for the conversion are on the market. A compression of 14:1 isn't streetable
    for gasoline fuel, might work on propane or E85.

    The greatest advantage of fuel injection on old engines is controlling emissions, it won't help
    mileage much. Good accurate spark will do more, perhaps with knock detector. Bruce Roe
    My idea is use the car with Ethanol, I already make it and is very cheap but in low compression engines the MPG will be 20% less than using gasoline. If i'm right a high compression ratio in some of cases equals to more MPG

    About the MPG using fuel injection in old motors I read in some place that using an EFI system the MPG can increase between 2 - 4 extra miles per gallon.

    I was looking for MSD systems and this looks good for me: http://www.ebay.com/itm/MSD-Ignition...6b025f&vxp=mtr But it seems made for Oldsmobile cars.

    I checked the air filter housing and seems to be something like a sensor on it but If i'm right this sensors is for injection engines and I think this is not a carburated engine

  13. #12
    cadillac_al is offline Cadillac Owners Connoisseur
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    Re: Cadillac Deville 74 472, increasing engine compression

    Welcome to the board Josehf. I think you have a good plan for your Cadillac since you live in South America and have access to pure ethanol. I think the fuel injection is a good idea too to get it dialed in much quicker and easier. I don't know all the math to calculate compression ration but like somebody already said, those older closed chamber heads should increase the compression ratio quite a bit and you may be able to shave them down a little more is needed. I hope your car has electronic ignition to make your life easier too. I'm sure the fuel injection kits will address that in some way. I hope it works out so keep us posted.

  14. #13
    Roadmaster75's Avatar
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    Re: Cadillac Deville 74 472, increasing engine compression

    An MSD 6A unit is a universal ignition box that will work on 4,6, and 8 cylinder cars.
    In the USA it's about $169-179. Get their coil too.
    I use that box on all my projects. If you have some extra $$ I'd pop for their Cadillac
    specific distributor with vacuum advance. It will attach to the 6A box with
    two simple wires. Then simply play around with the timing with your various fuels choices.

    Might be time to eliminate
    the tired old stock one.

  15. #14
    josehf34 is offline Cadillac Owners Member
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    Re: Cadillac Deville 74 472, increasing engine compression

    Quote Originally Posted by Roadmaster75 View Post
    An MSD 6A unit is a universal ignition box that will work on 4,6, and 8 cylinder cars.
    In the USA it's about $169-179. Get their coil too.
    I use that box on all my projects. If you have some extra $$ I'd pop for their Cadillac
    specific distributor with vacuum advance. It will attach to the 6A box with
    two simple wires. Then simply play around with the timing with your various fuels choices.

    Might be time to eliminate
    the tired old stock one.
    A question: What's the difference between this systems: http://www.ebay.com/itm/MSD-Ignition...e30fc1&vxp=mtr and http://www.ebay.com/itm/MSD-Ignition...f906ce&vxp=mtr

    A guy recommend to me change the torque converter, it says that I would get a better MPG and power if I change this part

    I Talked with a guy who owns a cadillac eldorado convertible 1959 and it told me it actually do 14MPG with him caddy

    What the experts recommend?

  16. #15
    steelybill is offline Cadillac Owners Enthusiast
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    Re: Cadillac Deville 74 472, increasing engine compression

    An MSD ignition is probably over-kill on an engine that wont likely see 4500 RPM.

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