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500, 472, 425, 368 Discussion, cheap power improvements to the 425... in Cadillac Engine Technical Discussion; I got a line on hopefully some 68 parts. How can I confirm that the intake and exhaust manifolds are ...
  1. #91
    BigPoppaD is offline Cadillac Owners Member
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    Re: cheap power improvements to the 425...

    I got a line on hopefully some 68 parts. How can I confirm that the intake and exhaust manifolds are truly the correct parts?

  2. #92
    djcwardog's Avatar
    djcwardog is offline Cadillac Owners Member
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    Re: cheap power improvements to the 425...

    Quote Originally Posted by BigPoppaD View Post
    I got a line on hopefully some 68 parts. How can I confirm that the intake and exhaust manifolds are truly the correct parts?
    I had this data in my spec lists - no guarantee that I have it right, but this manifold works on my car:

    1605061 is a 472/500 stock cast iron with EGR – replaced 160955 stock 425 “negative rise” piece.

    I also had this from a web poster:

    ‘68-mid’70 engines used the first generation heat operated choke, with an exhaust passage around the front of the carb. These intakes have a cast rectangular box-shaped choke well. Mid’70-’73 engines do not have the heat passage around the carb, and have a round choke well with what looks like a freeze plug in the bottom of it. (This describes mine) Many ‘68-’70 engines also had no EGR valve. All OEM 472/500 intakes are dual plane.

    I surmise that I have a mid '70-'73 intake...

    I don't have the parts numbers for the exhaust manifiolds. You want those that have a nice thick front runner (by this I mean the exhaust tube for #1 and #2 cylinder). The ones to avoid are the stock 425 pieces which have huge dimples cast right in on both the left and the right front runner.

  3. #93
    deVille33 is offline Cadillac Owners Connoisseur
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    Re: cheap power improvements to the 425...

    Wow! This post has a lot of history and a lot of info. There was someone selling crossmembers he manufactured for A bodies. The sugestion made here for the later C body looks good. Still available from GM?
    ONe thing I thought of, You can change your cam's performance by adjusting cam timing by a couple degrees. You don't neccessarily have to give your money to a cam company for a mild timing change.

  4. #94
    cadillac_al is offline Cadillac Owners Connoisseur
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    Re: cheap power improvements to the 425...

    Hey djcwardog, do you have any timeslips yet? Please let us know how the mods worked out.

  5. #95
    steelybill is offline Cadillac Owners Enthusiast
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    Re: cheap power improvements to the 425...

    The after market cam guys like Comp Cams advise advancing the cam timing by like 4 degrees for low-end power, and retarding the timing by about 4 degrees for higher RPM power. There is no magic power boost in fooling with cam timing in general. Most folks install new cams "straight up", meaning the timing marks on the cam drive sprockets are lined up like an overhaul manual specifies, as opposed to setting it up with a degree wheel etc, for getting all available power.

  6. #96
    BRICKS is offline Cadillac Owners Fanatic
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    Re: cheap power improvements to the 425...

    im gonna try out a few of these and see what happens from there.

  7. #97
    sleutelgek is offline Cadillac Owners Member
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    Re: cheap power improvements to the 425...

    Hello i buy a 2115 edelbrock intake for my 79" 425 cid coupe.
    What gasket sal i take the edelbrock?
    Or can i take a splasch pan a 425 or a 472?
    I like splasch pan the intake are not too hot to.


    thanks for your recomendations.

    greeting Danny from holland (europe)

  8. #98
    BRICKS is offline Cadillac Owners Fanatic
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    Re: cheap power improvements to the 425...

    anyone have a price range for the intake? had someone tell me 200+ shipping on a 500 intake and 50+ shipping on the ac compressor bracket. a little much with shipping. picked up a caprice sway bar to switch over. just need a couple more goodies.

  9. #99
    deVille33 is offline Cadillac Owners Connoisseur
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    Re: cheap power improvements to the 425...

    Quote Originally Posted by steelybill View Post
    The after market cam guys like Comp Cams advise advancing the cam timing by like 4 degrees for low-end power, and retarding the timing by about 4 degrees for higher RPM power. There is no magic power boost in fooling with cam timing in general. Most folks install new cams "straight up", meaning the timing marks on the cam drive sprockets are lined up like an overhaul manual specifies, as opposed to setting it up with a degree wheel etc, for getting all available power.
    Your correct here. My statement, "changing performance", was wrong. Advancing or retarding the cam's degree of timing is a torque curve adjustment.
    In the 1980s or sooner GM started changing the torque curve of the cams to enhance mileage, which made performance off the line anemic. Degreeing a cam is not magical, but you have to understand valve train dynamics and other aspects of your engine/drive train to maximize your performance / economy.

  10. #100
    gornati's Avatar
    gornati is offline Cadillac Owners Fanatic
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    Re: cheap power improvements to the 425...

    anything for the 425 fuel injected?
    i have a 1978 EFI, but all i done if to put new plugs, change oil, fix the ECU, new air filter, new oil filter, new stainless steel headers and 2.5" exhaust with a flowmaster super 40 series...

    anything else you guys would recommend?

  11. #101
    DouglasJRizzo is offline Cadillac Owners Enthusiast
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    Re: cheap power improvements to the 425...

    Quote Originally Posted by gornati View Post
    anything for the 425 fuel injected?
    i have a 1978 EFI, but all i done if to put new plugs, change oil, fix the ECU, new air filter, new oil filter, new stainless steel headers and 2.5" exhaust with a flowmaster super 40 series...

    anything else you guys would recommend?
    The EFI on 75 - 79 cars was primitive by todays standards. However, waking up a 425 EFI motor cant be too hard. People here have mentioned degree-ing in the cams and I think that would do a lot. One thing I've noticed about Cadillac camshaft profiles is that they are hyper mild.

    Oh, one other thing. The EFI on the regular car line was different from the EFI on the Seville.

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