Spark plug gap

JasonNC
JasonNC Expert Adviser
edited November 2013 in HUDSON
I'm having a problem with the #2 spark plug. The gap keeps going closed. About a month ago it did the same thing one time on #3, but this is the second time in two weeks that it's happened on #2. The car runs great until that plug goes closed and then it starts to miss. Any suggestions as to cause and what can be done to stop it?

Comments

  • ESSX28-1
    ESSX28-1 Senior Contributor
    edited November 2013
    Are they closing due to being touched by piston/valve? Have you changed plugs recently?
  • JasonNC
    JasonNC Expert Adviser
    yes. The plugs are new.
  • RL Chilton
    RL Chilton Administrator, Member
    It could only be one of two things: a defective plug (not likely) or it's being hammered closed. I would take it out and compare it to another plug very carefully. Make sure the threads are the same length. If so, shine a light into the empty spark plug hole and crank the engine slowly to see if the plug could be being hit.

    I'd try replacing it anyway (first) and see if another plug does the same thing.
  • [Deleted User]
    [Deleted User]
    Is your cylinder head under 1inch 40 thousands. There is your problem. Walt.
  • RL Chilton
    RL Chilton Administrator, Member
    Walt-

    Don't you mean 1.940"?
  • lostmind
    lostmind Expert Adviser
    If you didn't have the situation before you changed the plugs, compare the new with the old to find the difference, Maybe the gasket is to thin.
  • Geoff
    Geoff Senior Contributor
    Check the plugs that they are H10's. If so then you have too thin a head and the valves are donging the gaps shut. If not H10's, it could be that the electrodes are too far extended down.
  • JasonNC
    JasonNC Expert Adviser
    Geoff, Funny you should mention H-10's because that is exactly what I had the O'Reilly clerk order when he was trying to sell me NGKs. After I got them, my mechanic told me that Champion is the worst plug made. He's got one more time to tell me something AFTER the fact and....
  • RL Chilton
    RL Chilton Administrator, Member
    Jason-

    I'm sure there is nothing wrong with your plugs, and the problem is elsewhere. There's nothing wrong with Champion plugs, per se.
  • SuperDave
    SuperDave Senior Contributor
    I did have problems with Champions over 30 years ago on GM products. Had to go to A/C to solve problems, but never a problems with the H series. Be aware that plugs with the "UN" in the prefix have an internal gap inside the insulator that can give you fits with timing issues.
  • ratlee2
    ratlee2 Expert Adviser
    Could this be corrected by using indexing washers on the spark plugs to move the plugs away from the pistons or valves.

    Rich
  • EssexAdv
    EssexAdv Expert Adviser, Member
    edited November 2013
    Get a J8 Champion and put it in the #2 spot. The J8 is shorter reach than an H series. If this fixes the problem then the piston or valve is hitting the plug. If not, it is as others have suggested.

    P.S. What motor are we discussing??
  • RonS
    RonS Senior Contributor
    I've been watching this. Jason are you talking 308? Is the engine making any unusual noises ... Like tapping or rapping ? A piston hitting a plug should be audible with a sound device even a stethoscope. Try switching the plug with another. If the plug is too long it will repeat at the new location. Is there any drivability issues before it begins to miss? If the new plug in the suspect hole flattens , as did the first, put a second gasket on it and try. I am wondering if a con rod is loose and sending the piston erratically high on compression stroke, or a valve spring keeper dislodged. These engine designs have a lot of space for pistons and valves to miss the plug... not like interference engines of today. This can be serious. If that electrode falls into the combustion chamber, look out below.
  • Geoff
    Geoff Senior Contributor
    There is no way the piston could affect the plug - it is a side valve- go figure!
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