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spark plugs and gapping

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by mud390, May 17, 2003.

  1. mud390

    mud390 1/2 ton status

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    I'm about to do a tune up on my 77 K5 with a 350. I've got AC Delco plugs and I have been told that 45 thousandths is the best gap distance. What do y'all run? Also, what do closing or opening up the gap do for performance? Thanks guys!
     
  2. bee32

    bee32 1/2 ton status

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    Mine run around 42. What did the part store tell you or what does your manual say? That's where I get my info.
     
  3. mud390

    mud390 1/2 ton status

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    I got the plugs at Auto zone. I don't have a manual... I think it fell through a rust hole somewhere in the truck. I thought 45 thousandths sounded a little on the high side.
     
  4. bee32

    bee32 1/2 ton status

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    /forums/images/graemlins/rotfl.gif Rust hole. Sounds like mine. I am looking at my gapper on my keychain and most marks end at around 35-42. Somwhere in there and you should be okay. Check the color of them after drivin it for a few days.
     
  5. mud390

    mud390 1/2 ton status

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    Thanks for the help!
     
  6. bee32

    bee32 1/2 ton status

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    No Prob! Good luck /forums/images/graemlins/thumb.gif
     
  7. Hossbaby50

    Hossbaby50 3/4 ton status

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    I have got mine gapped at .053 right now. I will up it .060 or .065 when I get back to AZ. But I run full MSD ignition so I can run alot wider gaps. I also run Champion Truck Plugs that are a stage hotter then normal. They are number 4018's. They work very well for me. I have been running them (different sets) since 1997.

    I think stock is .045
     
  8. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    45 is what HEI is specked. SHould be a sticker on the core suport of the air cleaner. both my 75 and 79 are .045.
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

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    Run mine at .050" no problem, and some real low (7.9-8.2 or so) compression GM engines had .080" gaps.

    Supposedly Chev had a problem burning up coils with the .045" gap, which is why they went back to .035 (what is spec'd for the 9.2:1 305's for instance, IIRC), but I find that hard to believe, since Oldsmobile was running at least .060" on the exact same PN coil.

    Haven't burned up my Chev coil in 3+ years, and it's a used unit, so I don't think I buy into the wider gap/less coil life idea. More likely, problems with ignition as the compression finally started to rise again.
     
  10. big pappa b

    big pappa b 3/4 ton status

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    Like Grim said, .045 is the average for a stock electronic ignition. The older points distributors were normally around .035
    High performance ignitions can run a wider gap
     
  11. monte0172

    monte0172 1/2 ton status

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    somewhere between 40-45 is cool!!! I have ran mine liket that for years and never had a problem.
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

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    [ QUOTE ]
    Like Grim said, .045 is the average for a stock electronic ignition. The older points distributors were normally around .035
    High performance ignitions can run a wider gap

    [/ QUOTE ]

    Did you read my post? I already said that later vehicles were running .035" *again*, and nowhere in my post did I say that I'm running an aftermarket ignition to jump the .050" gap. As a matter of fact, I stated that a Chev coil (HEI if that wasn't clear) can easily work with a .060" gap.

    Sorry if that doesn't come off as friendly, but you are not correct, and since we are posting info so people can make up their own opinion, in this case on what gap they want to run, you need to post correct info.
     
  13. TopOff

    TopOff 1/2 ton status

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    The bigger the gap the better the performance the worse the gas mileage.

    IIRC every .05 bigger gap gets 2% better power and 2% less gas - or something to that affect.

    Good luck.
     
  14. Panther

    Panther 1/2 ton status

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    I'll open a can of worms here since I'm having trouble with this myself.....

    Is it better to widen or close the gap if the engine is fouling plugs?? I know, I know, fix the problem, don't band-aid it, but I wondering what would fire easier through oil.
     
  15. 84_Chevy_K10

    84_Chevy_K10 Banned

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    They make anti foulers for engines with oil control problems (autozone in the help section). JC Whitney has plugs that'll fire in oil, too.
     
  16. dyeager535

    dyeager535 1 ton status Premium Member

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    The narrower the gap the easier it is for the spark to jump it (you'd narrow the gap running nitrous for instance) but the wider the gap, the less likely the plug is to become fouled, supposedly.

    Spark plug gap is something you can play around with, kind of like timing, when you get to the point of small changes, it's very engine specific, and very small, if any, noticeable differences.
     
  17. Panther

    Panther 1/2 ton status

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    Are those the sleeves that thread into the block and then the plug threads into those so the oil doesn't actually leak onto the plug? I read about those when my old Blazer had a fouled plug. I couldn't find them at the time though. I will check Autozone for them. Thanks 84 (and Dorian) /forums/images/graemlins/grin.gif .
     

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