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  1. #11
    Legend

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    I understand the the whole AC Delco thing, but I know when you go down to an auto parts store and get plugs they say .060 GAP for the 5.7 so why go down to .040
    99 K1500 Suburban LT "THE BEAST"
    Hypertech III, K&N, true dual
    285/75/16
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  2. #12

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    Quote Originally Posted by 2COR517 View Post
    Those big gaps puts a tremendous load on the entire ignition system. Coil, cap, rotor. GM issued a bulletin some years ago to crank the gaps back down to .040. I did it in my truck, made a huge difference.
    Apparently it wasn't a TSB, but something they issued through their dealer network. It probably takes five times the energy to spark the larger gap.
    When you hear hoofbeats, look for horses not zebras.

  3. #13
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    North central IN. Macy
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    You might want to chk those wires out again. I got a poor set from the zone 1 time yrs ago. I do not use inexpensive ignition parts anymore. Don't pay!

  4. #14

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    Quote Originally Posted by wildolman View Post
    You might want to chk those wires out again. I got a poor set from the zone 1 time yrs ago. I do not use inexpensive ignition parts anymore. Don't pay!
    Same here! AC Delco all the way. They are actually cheaper than Napa. NAPA BlueMax wires are OK though.
    Last edited by 2COR517; 07-08-2009 at 10:25 AM.

  5. #15
    Legend

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    So what was the difference by going to a smaller gap, did you notice better starting, or difference in MPG or throttle response

  6. #16

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    Everything is better. Most noticeably ilde is smoother, no more pinging/detonation, and more power overall.

    Apparently, GM tried big gaps in the 70's, 80's, and 90's. And each time after a few years they issued new guidance to take the gap down to .040.
    Last edited by 2COR517; 07-08-2009 at 02:05 PM.

  7. #17

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    The problem is not the plugs, wires, cap, etc as i swapped them out already with no change. i will start preparing for the leak down test and see what it shows. thanks for all of the replys.

  8. #18

    Default similar issue

    Quote Originally Posted by L0sts0ul View Post
    check your compression, sounds to me like a head gasket leak on possibly both sides or even a crack in the block... could be a craked head too...
    coolant in the exhaust (in my experience) has always come from cracked heads, or head gaskets.
    I have no coolant in my exhaust, though...thoughts?
    Carbon footprint? What carbon footprint?

  9. #19
    Sr. Apprentice hmaster77's Avatar
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    Kingsville/San Marcos TX
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    the gapping will stop the miss fire but the coolant leak is more than likely a blown or leaky headgasket or cracked head does the van ever overheat?
    2008 chevy silverado single cab short bed 4.3
    1960 chevy apache 10 single cab short bed 3.9
    1986 chevy 1 ton flatbed 5.7 (deceased)
    1990 suburban regency edition 5.7 (sold

  10. #20
    Jr. Engineer
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    Quote Originally Posted by 2COR517 View Post
    Apparently it wasn't a TSB, but something they issued through their dealer network. It probably takes five times the energy to spark the larger gap.
    This is the exact reason to use the MSD 6 box with msd coil, and wires. I have successfull run .065 gap using this setup, and haven't had any problems.

    1993 K1500 Suburban 350TBI, 378,486KMS on frame, 49,000KMS on Drivetrain. Lots of mods, built for haulin trailers and haulin @$$ :)

    2000 K2500 Yukon XL 6.0L Vortec 252000KMS custom CAI, and exhaust...but not done yet.

    "If you are dumb enough to do something you don't know how to do, and can't do it safely then WHEN you get hurt its your own fault...BONEHEAD"

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