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Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by santana, Jun 11, 2003.

  1. santana

    santana 1/2 ton status

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    I'm getting conflicting facts on spark plug gaps, .035, .045 .060..... I've got a 350 and the label on the rad support is for a 305, it shows .045 for the gap and I'm wondering what the actual gap should be for a 350 with an HEI. I pulled one of the plugs and its gapped at .035. Is this right?? /forums/images/graemlins/confused.gif Also the F'r misses at idle and diesels plus it lacks power.. I want to replace the plugs so I can set the timing and see WTF is going on with it. If anybody has any opinion on what could be happening I'm all /forums/images/graemlins/ears.gif /forums/images/graemlins/thumb.gif /forums/images/graemlins/k5.gif
     
  2. Bubba Ray Boudreaux

    Bubba Ray Boudreaux 1 ton status

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    The book says .035 for an '89......
     
  3. santana

    santana 1/2 ton status

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    89, That would be TBI tho, mine is carbed 350 w/HEI.. Is it the same gap as a 305?? /forums/images/graemlins/ears.gif
     
  4. 77Jimmy

    77Jimmy 1/2 ton status

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    I can't help you on your gapping question, but I had a problem w/ dieseling too. I replaced all my plugs, set the timing, and adjusted the idle down to around the 650-700rpm range. That took care of the dieseling problem.

    Then I adjusted the mixture by the screws on the carb...w/ engine running I screwed them both in as far as they would go, engine would die, screw both of them out a half turn, crank the engine, if engine died I'd screw both of them out another half turn. I repeated this process until I got the engine to idle around 650rpm.
     
  5. santana

    santana 1/2 ton status

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    Right, that is why I'm looking for the gapp size so I can set the timing correctly /forums/images/graemlins/rolleyes.gif.. I don't want to gap the plugs wrong and not get the proper timing set, I don't want to end up right back where I started from. /forums/images/graemlins/smirk.gif... /forums/images/graemlins/ears.gif..... /forums/images/graemlins/1zhelp.gif.....

    Jerry..
     
  6. Bubba Ray Boudreaux

    Bubba Ray Boudreaux 1 ton status

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    Everything with a carb says .045.....
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    You can try increasing and decreasing the gap to see if one works better than another. HEI will jump a gap anywhere up to .080". (and likely more)

    In reality, I doubt you will see a big difference no matter where it's gapped, as long as its not excessively small or excessively large. But I believe the GM HEI gap specs went from .035" minimum up to .080" max.

    Supposedly the larger gaps cause decreased coil life, but since other GM makes spec'd .060" on the exact same coil that Chev used for .035 or .045", I don't believe it makes enough difference to worry about.
     
  8. NITRO

    NITRO 1/2 ton status

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    if u have a restrictive exhaust, it can also lead to dieseling. just a thought

    NITRO
     
  9. santana

    santana 1/2 ton status

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    Thanks fellas, that pretty much clears it up. I picked up a new set of plugs and the dude at the parts store said the gap is .045. I'llgo with that and re-set the timing and see if that takes care of the problem.. /forums/images/graemlins/thumb.gif

    Jerry.. /forums/images/graemlins/k5.gif
     
  10. blasterD

    blasterD 1/2 ton status

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    I used to run .045 on my 350 It seemed to work well. Now I run .060 but I have an MSD 6, Blaster coil, and an MSD HEI. I use the Accel u-groove plugs with the longer reach, sorry I cant remember the p/n. It starts quicker and runs much smoother now.
     

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