HEI conversion
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500, 472, 425, 368 Discussion, HEI conversion in Cadillac Engine Technical Discussion; Hey guys I'm sorry I know these have been posted everywhere before, but I want to make sure my specific ...
  1. #1
    Arseassin is offline Cadillac Owners Member
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    HEI conversion

    Hey guys I'm sorry I know these have been posted everywhere before, but I want to make sure my specific situation is applicable before I make an investment.

    I'm about to go ahead and purchase an HEI distributor to throw in my '70 472 and I'm seeing them on Ebay for around $200, is this a reasonable price?
    I've noticed conversion kits for the points system but from what I understand its better to simply drop in a new dist all together. I've also noticed that you can buy a non refurb dist from a 472 '75-'80 and drop that one straight in for the same effect?

    Which route would you guys recommend, also how much should I expect to pay someone to get this thing set up for me?


    I know I'll have to get new plugs at .60 and new wires as well.

    I appreciate the help in advance.

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  3. #2
    deVille33 is offline Cadillac Owners Connoisseur
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    Re: HEI conversion

    The stock GM HEI unit for your application should work fine. This includes the 472 to 1976 and the 425 from 1977 - 79. Go to any pick and pull and you can probably get everything for $50,00. But be prepared. Read some of the threads in here and you will see there are sometimes difficulties in removal of the unit from the block. You should also get the 10 gauge wire that comes up from the starter. If your paying someone else to do all this, plus rewire your car and set your timing $275.00 would not be unreasonable.

  4. #3
    70eldo's Avatar
    70eldo is offline Cadillac Owners Connoisseur
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    Re: HEI conversion

    If I may give you some advice I was informed the HEI will not bring you much extra performance (unless you did some other major tuning to your engine). You will be better off going with the electronic ignition conversion built in your stock distributor. It will replace the points type ignition so it will save you on points adjustments (which hardly anyone left will be able to do this properly) and will provide better ignition timing throughout the rpms.

    Those go for about $120-140.

  5. #4
    The Ape Man's Avatar
    The Ape Man is offline Cadillac Owners Connoisseur
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    Re: HEI conversion

    HEI is a very worthwhile conversion.

    Sometimes there are issues with dual belt AC/PS pump cars.

    I suggest keeping your existing vacuum advance and mechanical advance if the car runs OK now. HEI setups from later cars usually use very different vacuum signals.

    The vacuum canister will swap over from youe existing distributor. The mechanical weights and springs should also. Look for a distributor without a lot of mechanical play in the advance mechanism. Some are so bad as to be hopeless. They are good to about 300k miles IME.

    Later you can play with tuning.

    The factory setups can be found in 74 Eldorado and reportedly Deville models, 75 - 80 All cadillac models except for Olds powered like Seville and '79 up Eldorado. Some Kalifornia models have stuff you don"t want but these are rare to run into.

    Get the ignition wires too. Always twist the spark plug boot before pulling it off the plug. Otherwise the wire can break internally.

    Grab the B+ feed wire because you want the plug.

    Many insist on replacing the resistance wire left over in the car as used with the points distributor or the world will end. Fact is the HEI draws a lot less current than the points setups due to it's high efficiency switching and the voltage drop is not very much. I've done it both ways and had no issues either way.

  6. #5
    cadillac_al is offline Cadillac Owners Connoisseur
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    Re: HEI conversion

    HEI's are great, just make sure it won't interfere with your belts or pulleys. (I always thought it would.) If you need to change pulleys you may want to go with the Pertronix conversion.

  7. #6
    Submariner409's Avatar
    Submariner409 is offline If it won't run, stick on fender vents
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    Re: HEI conversion

    I use a Pertronix Ignitor or Ignitor-III in all my Delco distributor conversions for Olds 455 and GM 454 marine engine builds. Reliable, strong, accurate, simple. Use the Pertronix-recommended coil and ballast (if needed).

  8. #7
    The Ape Man's Avatar
    The Ape Man is offline Cadillac Owners Connoisseur
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    Re: HEI conversion

    Another possible advantage for the Pertronix might be the old points distributors don't have problems with binding mechanical advances like the Cadillac HEI units. I'm not sure of this one though.

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