Spark Plug Extenders, 328 GTS | FerrariChat

Spark Plug Extenders, 328 GTS

Discussion in '308/328' started by Lawrence Coppari, Nov 13, 2020.

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  1. Lawrence Coppari

    Lawrence Coppari Formula 3

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    #1 Lawrence Coppari, Nov 13, 2020
    While I await the return of my speedometer that was sent to Palo Alto for repair, I thought I'd check my original spark plug extenders that are now 33+ years old. Attached are two pictures of one of them, one taken through a magnifying glass. It was the first one pulled. Wonder what the rest of them look like.....

    Just to be sure is this the pinhole failure that others on this forum talk about?
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  2. smg2

    smg2 F1 World Champ
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    #2 smg2, Nov 13, 2020
    Looks like a high voltage burn thru.. honestly though I use a high pot tester to check. I realize that most don't have that eq on hand or have experience using it. So the other option is to remove the silicone boot cover (pita) install and then run the engine at night or in the dark and look for coronal discharge.

    Or inspect and check for 'burn' marks, assume them bad and replace. They are wear items... The high voltage wants to go to ground and will find the path of least resistance. Plugs are not the path of least resistance.
     
  3. Lawrence Coppari

    Lawrence Coppari Formula 3

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    #3 Lawrence Coppari, Nov 13, 2020
    The last time I checked my extenders I did not see anything like this on them. I've only looked at the rear bank so far and have two that exhibit what is seen in the picture. The pictures posted are of the same extender, one shot through a magnifying glass. They are 33+ years old. I'm ordering a new set.
     
  4. miketuason

    miketuason F1 World Champ
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    #4 miketuason, Nov 13, 2020
    Doesn’t look like a burnt hole, do you have a pic of the other side (inside)?
     
  5. Lawrence Coppari

    Lawrence Coppari Formula 3

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    #5 Lawrence Coppari, Nov 13, 2020
    I'll take a picture of the inside that will show the area corresponding to the mark on the outside. Will post shortly.
     
  6. Lawrence Coppari

    Lawrence Coppari Formula 3

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    #6 Lawrence Coppari, Nov 13, 2020
    The pinholes that appear on the outside are at 6 o'clock. I don't see anything on the inside that looks like what is on the outside. But there is a dark ring and a little black dot at about 4:30 a little farther inside. Image Unavailable, Please Login
     
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  7. miketuason

    miketuason F1 World Champ
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    #7 miketuason, Nov 13, 2020
    Yea, I’m still not convince the hole is all the way through but like what smg2 said, start the engine in the dark and looks for sparks jumping to ground. If it’s burnt through it should look like this. Image Unavailable, Please Login Image Unavailable, Please Login
     
  8. Lawrence Coppari

    Lawrence Coppari Formula 3

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    #8 Lawrence Coppari, Nov 13, 2020
    That is quite a difference. I'll do the test in the dark. Thanks.
     
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  9. smg2

    smg2 F1 World Champ
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    #9 smg2, Nov 13, 2020
    That's massive burn thru... They start small... Then get bigger....
    "That's what she said!"

    Seriously.. They are not always obvious at first, breakdown starts near sharp points and edges, the dark ring is carbon burn from the electrical discharge. It's also prone in that location if the extender does not get a positive lock on the plug, then it has to arc across..

    Oh and ohm meters are useless for high voltage testing of resistance... That requires a very different rig. And the extenders are just a brass rod anyway so nothing to test.
     
  10. Lawrence Coppari

    Lawrence Coppari Formula 3

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    #10 Lawrence Coppari, Nov 14, 2020
    OK, smg2, you've convinced me. I'm definitely ordering a new set.
     
  11. Brian A

    Brian A F1 Rookie

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    #11 Brian A, Nov 14, 2020
    It is remarkable how large the clip spring is on these original extenders. Modern ones (such as from Kingsborne) have much smaller diameter spring clips and therefore keep the voltage farther away from grounding to the metal of the engine head.

    Some people demonize extenders. It seems to me (no empirical data) that the only real problem is suboptimal clip design of the original ones.
     
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