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Spark plug gap Question

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Redfrog, Jul 6, 2001.

  1. Redfrog

    Redfrog 1/2 ton status

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    I'm going to put in new plugs in tomarrow. I believe the the gap
    is 45 what would happen if I opened it up to about 60? with a stock HEI system, any benefits or draw backs? I heard that it would help but I wanted to find out before I did it.TIA




    HEY Fords!!! how many flushes does it
    take to get rid of you
     
  2. 84_Chevy_K10

    84_Chevy_K10 Banned

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    I can think of no benifit. Drawbacks? Harder on the coil, needs more voltage to jump more gap. Also as the plugs wear, the gap opens up even more, making it harder and harder for it to fire....eventually it might not run, but I doubt it, I've seen gaps open to .090" and the engine still ran.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  3. POWERMAD

    POWERMAD 1/2 ton status

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    I am running Accel supercoils on my rigs and I am running the plugs at.045
    I wouldn't open them up anymore than that.

    my truck's not dirty, it's earth tone paint
     
  4. jarheadk5

    jarheadk5 1/2 ton status

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    IMO, running a bigger plug gap on a stock HEI isn't productive. Now if you had, say, an MSD ignition box with an MSD Blaster coil, you could open up to like .050-.060 and see improvements...

    If at first you don't succeed, failure may be your style...
    [​IMG] <font color=green>Semper Maintenance!<font color=black>
     
  5. bablazer73

    bablazer73 1/2 ton status

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    a wider gap creates a hotter spark IF you have an ignition that will run it. A stock HEI wil not. even with a "performance coil I wouldn't do it. If you are running a msd box or similar you could.

    your right. I don't understand the jeep thing!
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    Not to be argumentative, But thats not even remotely true.

    I would just like to point out one of the "myth's" regarding GM's HEI and MSD's. GM HEI is ENTIRELY adequate for a non high revving motor. (I personally say 7000RPM or less, but even 4500 is high enough for the average truck enthusiast) At the higher RPM's, coil saturation times on the GM unit are too high, causing misfires.

    As to .060 being too big, GM used .060 gap on Olds V8's with HEI (late 70's for example) with the same coil in cap that the chevy's used. I would run whatever GM says to run ON YOUR MOTOR though, I'm just pointing out the fact that .060 isn't too much for stock HEI. Has more to do with plug placement and combustion chamber design than it does with any supposed shortcomings in GM's HEI.

    Again, not here to piss anyone off, just point out some facts : )

    Dorian
    My tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
    No anti-theft measures on your truck? No pity when its stolen
     
  7. bablazer73

    bablazer73 1/2 ton status

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    ok. I didn't know that. I was only repeating what was told to me from MSD. I called them as to what plugs/gap would be best to use with there 6al box in my engine.

    your right. I don't understand the jeep thing!
     
  8. CaptCrunch

    CaptCrunch 1/2 ton status

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    I agree w/ Dorian... HEI is sound... but I think a mad coil is a good upgrade for the price... especially considering alot of our rigs have 150+ miles on them and are ten plus years old... so I think a new coil in general might not always be a bad idea. I run .060 w/ my msd offroad system and like it... I would just recommend getting the coil and let the HEI control it.... spend the other cash on some good high quality wires (like msd's or taylors IMO) and some beer for after the tune up [​IMG] LOL

    -Mikey
    1987 Chevy K5 Blazer- 350 TBI
    <A target="_blank" HREF=http://www.geocities.com/milnerlives_2000/blazer.htm>http://www.geocities.com/milnerlives_2000/blazer.htm</A>
     
  9. shawnboy

    shawnboy 1/2 ton status

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    The rule of thumb is the larger the gap the cooler the plug. On a stock HEI ignition the gap should be .035".
    If you run an MSD or Accel etc. at .035" you will notice a rough idle and occasional misfire under load. .045"
    to .055" is recomended for the hot boxes and please stay away from the hype plugs like the platinum 4's. On a hotter ignition you will run the risk of melting a valve(s) or a piston(s).
    Shawnboy.

    If you are having to much fun it's probably illegal.
     

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