73 500 assistance

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500, 472, 425, 368 Discussion, 73 500 assistance in Cadillac Engine Discussion; I used to be a caddy engine freak, in fact I had three at once just sitting waiting for projects ...
  1. #1
    Curtis Mittong is offline Cadillac Owners Member
    Automobile(s): none
    Join Date
    Mar 2011
    Austin, Texas, United States,

    73 500 assistance

    I used to be a caddy engine freak, in fact I had three at once just sitting waiting for projects Its been so long that cadillacforums must have deleted me so I made a new account.

    Anyway... I'm getting conflicting answers and my memory isn't the greatest. I'm thinking about buying what the seller is calling a 73 500. He's an aging machinist who built the engine in 1995 and the customer never came to get it so he wants me to have it cheap.

    I consulted my old MTS tech book and it says that the 500 in 1973 was the low compression, but then later it says that all 68-73 were high compression. Since I will have to travel 3 hours to go look at it, what do I look for? Head castings? I'll take a welding rod with me to measure stroke, but what else should I check out? Are there heads that are particularly good or bad?

    I'm actually planning a bit more for it than what he has done, I just want to be sure I'm getting a good starting point.

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  3. #2
    cadillac_al is offline Cadillac Owners Connoisseur
    Automobile(s): 70 Deville 77 Fleet 78 Seville 92 Deville 03 Deville
    Join Date
    Feb 2007

    Re: 73 500 assistance

    Everything after 72 (maybe71) had lower compression and hardened valve seats for unleaded fuel. I don't think I would personally want a high compression version now and the 73 on the cheap should be an excellent starting point. I think the 500's had "500" cast above the oil pan rail.

  4. #3
    intragration's Avatar
    intragration is offline Cadillac Owners Fanatic
    Automobile(s): 1970 Coupe DeVille, 2002 Eldorado Collector Series
    Join Date
    Feb 2008
    Northlake, IL

    Re: 73 500 assistance

    There is no way to tell the 472 and 500 motors apart externally, except for the stroke test. The blocks are the same, except that I believe some early '70 472s may have continued to use the old block until supplies were exhausted. Compression went down in '71. I'd imagine the valve seats went hardened at the same time. There's really no problem with the high-compression motors, I have no problems with my '70, I just use premium and add lead substitute every tank to be safe. If this motor is cheap and rebuilt, it's hard to go wrong, unless it's been sitting outside since 1995.

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