Quadrajet ????

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  • 1 Post By Roadmaster75
500, 472, 425, 368 Discussion, Quadrajet ???? in Cadillac Engine Discussion; I have a 425 out of a 77 fleetwood in my 64 ford F100. The quadrajet started leaking. I have ...
  1. #1
    fordillac64 is offline Cadillac Owners Member
    Automobile(s): 64 Ford f100 425 Cadillac powerplant.
    Join Date
    Sep 2013

    Quadrajet ????

    I have a 425 out of a 77 fleetwood in my 64 ford F100. The quadrajet started leaking. I have been told it is very common for these carbs to warp over time and they are pretty much junk at that point. Is this true?

    Next, I decided to put a Holley(dont knock me down here) on it as I understand these a bit more. Well obviously the Holley is wider than the Quadrajet. Everyone I have talked to says all I needed was a spread bore to square bore adapter, so I did. Tonight I went to install it and come to findout it will not work. Are the Chevy Quadrajets the same width as a Cadillac's? Just wondering since I have had many Chevy guys tell me all I needed was this adapter to make it work.

    Bare with me here. Carbs are my week point on motors but im stubborn so not giving in. Plus I am not real familiar with working on GM material. :/

    Any info is very much appreciated!!!!


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  3. #2
    jukelemon's Avatar
    jukelemon is offline Cadillac Owners Member
    Automobile(s): 1968 Deville Convertible
    Join Date
    Jul 2013
    Louisville, KY

    Re: Quadrajet ????

    Quads are very nice carbs in the scheme of carbs. Not sure what people mean by "warp". If you torque down the carb too much, yes the base will warp but that is user error not the carb's issue.

    I would have just have bought the intended, stock carb for the 425 and not have worries about adapting this and that. But that's just me and what I did on the 68 Deville I just bought. 250.00 or so for a completely rebuilt, warranteed carb. Put it on, hooked up the linkage, and off it went without issue.

    But that is not where you are.

    Can you take the holley back? I have heard of Edlebrock's adapting on 425's but not Holleys. Not saying it cannot be done. Anything can be done lol.

  4. #3
    The Ape Man's Avatar
    The Ape Man is offline Cadillac Owners Connoisseur
    Automobile(s): '80 Fleetwood Coupe, 1994 and 1995 Mercedes 140 Coupe
    Join Date
    Feb 2005
    Southern NJ

    Re: Quadrajet ????

    I tried a Holley on a Cad 500 years ago. More soup than a Quadrajet but it really gunked up the intake valve stems fast. This with idle adjustment on a gas analyzer.

    I used an adaptor. What exactly does not work?

  5. #4
    Roadmaster75's Avatar
    Roadmaster75 is offline Cadillac Owners Member
    Automobile(s): 1978 Eldorado Biarritz
    Join Date
    Feb 2012

    Re: Quadrajet ????

    QuadraJets are good carbs. If it's leaking...fix it.
    Only use a Cadillac spec Quad as they are
    calibrated for specific applications.
    Rebuilding these is not rocket science
    and the procedures in rebuilding them are widely available.

    I have three Quads on the bench right now that I am about to rebuild.
    One Buick 455, a 75 Eldo, & a 78 Eldo.

    Go to Quadra-Jet parts.com and get a rebuild kit (about $30) and any other parts
    you think need replacing. You will have a correctly calibrated carb that bolts up
    without jerry rigging.
    The Ape Man likes this.

  6. #5
    Submariner409's Avatar
    Submariner409 is offline If it won't run, install big wheels !
    Automobile(s): 2002.5 F55 STS, 2014 Explorer XLT 4WD
    Join Date
    Feb 2006
    MD Eastern Shore

    Re: Quadrajet ????

    Get Doug Roe's HP paperback (8 X 11) book on Quadrajets. Everything you ever wanted to know. Google "rochester carburetors doug roe hp book".

    I build Olds 455 marine engines, and a well-tuned QJ is the only way to go - bulletproof, accurate, reliable. Install the electric choke upgrade.

    Don't try to get an 800 cfm QJ to run on a 425 - use the smaller primary venturi model rated at about 700 cfm or so - and learn how to set the secondary air valve tip-in spring tension.

  7. #6
    fordillac64 is offline Cadillac Owners Member
    Automobile(s): 64 Ford f100 425 Cadillac powerplant.
    Join Date
    Sep 2013
    Thread Starter

    Re: Quadrajet ????

    Thanks guys!!! I was MIA for a few days, crazy round here. I was handicapped and a bit inexperienced the night i was installing the adapter. I did go the Holley way. I was already invested into it so kept going this direction I also wanted to get it running so if I decided to sell the drivetrain out of the truck I can allow the potential buyer to here and drive it. The Holley works great so far. It is running a little rich but I have not made any adjustments yet. I bolted it on and it fired and idles real nice. I am going to hang onto the quad for the purpose of selling it with the motor. Or I may just attempt the rebuild for the knowledge and experience. It actually did not take too much modifying to make the Holley work. A couple "T" connectors for vacuum and the adapter plate. Again thanks for all the info.

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