Putting Humpty Dumpty back together
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500, 472, 425, 368 Discussion, Putting Humpty Dumpty back together in Cadillac Engine Technical Discussion; Hello. I havent posted in quite a while since my project was sitting due to no funds and no time ...
  1. #1
    The Butcher is offline Cadillac Owners Member
    Automobile(s): 1977 425 in a 1952 Merc (please dont shoot me)
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    Putting Humpty Dumpty back together

    Hello. I havent posted in quite a while since my project was sitting due to no funds and no time but I believe its time to start up again. I am building a 52 Merc and am putting in a 425 engine and matching tranny that was given to me by a good friend. The motor ran when the original Caddy was scrapped and it only has 60-something thousand miles on it. I removed everything down to the block but kept the crank and pistons in it. I have a brand new set of stock heads and a fresh stock intake but would like to get just a bit more power and thought that maybe a bolt in cam would be a great idea? What type of camshaft have you all replaced yours with and not gone crazy with the whole process? I would like to have a moderate street ride when I am done, but thought this motor is deserving of producing a bit more than the measly 180 it came with.
    I have removed the air cond unit and would like to run headers through some flowmasters.
    I know most of you recommended keeping and rebuilding the Rochester carb as well which is cool by me cause I think its a decent carb as well.
    Any advice would be greatly appreciated.

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  3. #2
    The Butcher is offline Cadillac Owners Member
    Automobile(s): 1977 425 in a 1952 Merc (please dont shoot me)
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    Thread Starter

    Re: Putting Humpty Dumpty back together

    48 hits and no responses............Has no one here ever freshened up a 425?

  4. #3
    deVille33 is offline Cadillac Owners Connoisseur
    Automobile(s): 1977 Coupe (blue), 1977 Coupe (yellow), 1977 Coupe (green)
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    Re: Putting Humpty Dumpty back together

    There are few options for the 425. Although it is a relative of the 472 / 500, it's downsizing comprimised the bigger engines' stronger points. The intake can be replaced with the Edelbrock, or other intake, which should help the induction over the stock design. This will allow a more aggressive cam. Don't go too wild, as the engine was engineered for torque rather than rpm's. With these changes you should change the jetting in the carb and some fine tuning with the ignition. I wouldn't suggest this if the engine was in a Cadillac, due to problems with hood clearance, but you are setting it into a different vehicle and you should be able to work that out accordingly. Are you building a ratrod? With $$$s you can enhance things further with a set of custom headers.

  5. #4
    The Butcher is offline Cadillac Owners Member
    Automobile(s): 1977 425 in a 1952 Merc (please dont shoot me)
    Join Date
    Jan 2010
    Location
    Brunswick, OH
    Age
    44
    Posts
    7
    Thread Starter

    Re: Putting Humpty Dumpty back together

    I appreciate the response. I was thinking along the same lines. I am building a rod, but I don't know if it will be a rat or hot rod. I love the idea of the custome headers. I see a fella on Ebay is selling custom stainless polished headers for the 425. They are buy it now for like 399 or something.......they arent cheap, thats for sure, but I was on the same page as you with the header idea.
    I want this to be more of a budget project and quite frankly I even tampered with the idea to keep everything stock on the engine and just run the headers back rather than sink unneccesary money into an engine that may already be more than powerful enough as she is going into a car that is 2000 lbs lighter than the original Caddy it came out of........in other words maybe Im making a mountain out of a molehill and I should just put the engine together and get on with the rest of the project already.
    Thanks for the advice and hope to hear from more of you with any thoughts.

  6. #5
    deVille33 is offline Cadillac Owners Connoisseur
    Automobile(s): 1977 Coupe (blue), 1977 Coupe (yellow), 1977 Coupe (green)
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    Re: Putting Humpty Dumpty back together

    These engines perform well when tuned properly. The biggest power robber with these engines is the miles of vacuum lines run off the engine. A large number of power options are operated off engine vacuum. It's amazing the idle speed can be set as low as it is. Running the engine in a rod will minimize vacuum robbery.
    Anytime you have one of these engines that is set with a high idle, and you try to adjust it, you find the engine will start to get erratic, start looking for vacuum leaks.
    In this regard, minimizing vacuum use opens the door to other enhancements. You can rejet / change needles in the carb and gain more in advance. The cam can be retarded to recurve your torque band. These are small adjustments that can be made to enhance performance without a lot of investment and on a stock platform. make your engine all that it can be.

  7. #6
    daniel58 is offline Cadillac Owners Fanatic
    Automobile(s): 58 Coupe Deville, 77 Coupe deville, 90 Deville
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    Re: Putting Humpty Dumpty back together

    I for one would be interested in pics of this project at any stage, particularly when you get it done. This was a common mod back in the day, Fordilliac I think they called them. There were even shops that specialized in putting Cad motors in old Fords. Personally I don't think you will need more power with this eng, you will have more problems getting the car to handle with the added weight and power. I hope you are doing some mods to the brakes as well as the rear end to put that power to the road safely and effectively.

  8. #7
    The Butcher is offline Cadillac Owners Member
    Automobile(s): 1977 425 in a 1952 Merc (please dont shoot me)
    Join Date
    Jan 2010
    Location
    Brunswick, OH
    Age
    44
    Posts
    7
    Thread Starter

    Re: Putting Humpty Dumpty back together

    Daniel,
    Thanks for the response. I will be taking pics along the way and will definately post them when it gets under-way (winter project).
    This is a total budget project as there is little money to be had right now, but she will get built.
    The motor is from 1977 and ran fine with only 60-some thousand miles on the clicker when my buddy pulled it to scrap the rest of the car. In that year, thanks to the EPA and gas crunches that monster block only produced 180 hp out of the factory. I figure with removing a lot of the polution control crap and AC unit it will run a bit stronger (more than enough for it to be a moderate street machine).
    The rear end gears in the Eldorado were (I believe) in the 260-something range and the gearing I have now are 373's..........that's a huge jump, but like many others have said, if I'm not wanting to go 120 mph and run it like an idiot it should be okay. If I find that the gearing is way too high in the rear, I can change them out to a lower gear ratio cheaper than the alternative which would be messing with the transmission to cooperate with the existing rear end gears.
    The brakes are disk in the front and drum in the rear (Malibu subframe in the front and Nova rear end in the back).
    This whole project was dropped on me and I feel a responsibility to rescue yet another dinosaur from a dusty garage and get her on the road again.
    I appreciate the advice and welcome anything any of you all can add to make my project a real gem.

  9. #8
    deVille33 is offline Cadillac Owners Connoisseur
    Automobile(s): 1977 Coupe (blue), 1977 Coupe (yellow), 1977 Coupe (green)
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    Re: Putting Humpty Dumpty back together

    Quote Originally Posted by daniel58 View Post
    I for one would be interested in pics of this project at any stage, particularly when you get it done. This was a common mod back in the day, Fordilliac I think they called them. There were even shops that specialized in putting Cad motors in old Fords. Personally I don't think you will need more power with this eng, you will have more problems getting the car to handle with the added weight and power. I hope you are doing some mods to the brakes as well as the rear end to put that power to the road safely and effectively.
    These mods that you speak of were made with the 390 c.u. engine, for which there was a lot of aftermarket and factory performance options. Dyers made blower adaptors for the 671 GMC. By the late 70's there wasn't muich interest in mating power options to a engine like the 425.

  10. #9
    daniel58 is offline Cadillac Owners Fanatic
    Automobile(s): 58 Coupe Deville, 77 Coupe deville, 90 Deville
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    Re: Putting Humpty Dumpty back together

    Yes deville33 power was not an issue with the 77 being the 1st downsized cad, they had other goals. On the other hand I question that 180 hp rating for the 77 as I have a 90 Deville 4.5 that also has 180 hp. The 77 when running correctly has much more top end than the 90 and seems more powerfull even though the 77 is 1000 lbs heavier. This has nothing to do with the thread I guess, those Fordilliacs used a new cad engine (at the time 1953) so they would have been even smaller than 390, perhaps even 331. Still a remarkable upgrade and a neat car. I really have no suggestions for performance, Butcher other that those mentioned. Increase intake and exhaust flow, good strong ignition and most important LOUD mufflers! A great project.

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