Spark plug wrong size?

Discussion in 'Technical' started by downhillbiker, Feb 15, 2012.

  1. downhillbiker

    downhillbiker Member

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    I ordered some e3 plugs and they are e3.42, which is supposed to be right, but I pulled one of the old plugs and it is an autolite platinum ap45. What is going on here?
     
  2. Bryant

    Bryant forgot more than learned

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    spark plugs like the e3 are a waste of money. what ever gain they give if any doenst make up for the high cost.
    as for the part number difference, i dont know if e3 uses the same numbers as autolite. they are 2 different company's and most likely use different numbers.
    i recommend getting plain autolite copper plugs
     
  3. downhillbiker

    downhillbiker Member

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    The e3 plugs I bought were $5.99 each. That is cheaper than many plugs. Plus they have a guarantee.

    I guess the question I should be asking is, are Autolite AP45's the right plugs for a 302?
     
  4. Mad Goon

    Mad Goon Scaring the Hondas

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    I had AP45s in the 302 in my Comet before. I might be crazy, but the engine seemed to idle smoother with those than with the Motorcrafts I have in there now.
     
  5. downhillbiker

    downhillbiker Member

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    Was that in stock heads? E3 , is saying the e3 42 is the right plug if heads are stock, but the A45 is like 3 sizes bigger in diameter.
     
  6. Bryant

    Bryant forgot more than learned

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    the 302 had 2 different size spark plugs. the easy way to tell which one you have is to see what size socket the plug needs. if its 5/8s or 13/16s. if both plugs use the same size they will fit. there are other differences in spark plugs. most important is the heat range of the plug. thats the only other difference that you may encounter but you most likely notice if you got a different heat range.
     
  7. Joe Dirt

    Joe Dirt BBF life

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    5/8 vs a 13/16 plug use what fits your heads
     
  8. downhillbiker

    downhillbiker Member

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    Is that the socket size or thread size difference? Because they are completely different thread, and it sounds like Bryant was saying socket size?

    [​IMG]
     
  9. Ryan

    Ryan Ford Addict

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    he was referring to the socket size. But the thread size is different. You got the wrong plugs. Return them if you can and just buy some regular copper autolites 45. No need to spend any more than that on a plug.
     
  10. Joe Dirt

    Joe Dirt BBF life

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    The large plug is a 13/16 hex 18mm thread
    The E3 is a 5/8 hex and 14mm thread

    In 74 ford switched from the large plug to the small plug
     
  11. baddad457

    baddad457 Member

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    The switch was in 1977 with the appearance of the D8OE heads.
     
  12. baddad457

    baddad457 Member

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    X2 on this Plain jane Autolite copper plus works as good as anything else on the market. Platinum plugs are designed only for those ignitions that fire twice, once on the firing stroke and again on the exhaust, the spark jumps backwards from what I understand on the exhaust and the platinum gets tossed back and forth between the electrodes. Don't know how true that is, but it sounds logical.
     
  13. simple man

    simple man Member

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    Never go by " what was in there "! Go by the charts for what engine and mods you have. Summit has one and I think Jegs does also! :)
     
  14. Joe Dirt

    Joe Dirt BBF life

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    Might want to recheck your source.
     
  15. Bryant

    Bryant forgot more than learned

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    the platinum plug is for long life. the double platinum plugs are for waste spark systems. they fire one plug from center electrode then the other from the ground strap.

    platinum doesnt wear out nearly as fast as copper does. thus it doesnt have to be changed out nearly as often as a copper plug does. platinum has a much higher resistance than coppers so it doesnt allow for as big of a spark that copper does.

    iridium plugs are supposed to be best of both. long lasting and allow for a big spark. there was a autolite spark plug tech who answered some questions about spark plugs and he really was pushing iridium plugs. he was supposed to send me a set to try out but they didnt have an application for the larger plug.
     

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