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  1. #1
    Jr. Apprentice bsharles's Avatar
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    Jul 2009
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    Humble, Texas
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    29

    Default 97 suburban plug gap

    I need to put plugs in my 1997 suburban 350 V-8, I haven't had it very long but the owner told me he hasn't put plugs in it for a couple years. I have heard that instead of the factory specs of .060 I should gap the plugs at .040 for better gas mileage, is this true? I want to do more but money says I can only do little things at a time and a/c repair and mirror and inside door handle fixes have taken a big bite out of the cash I had so I'll do little things as I can...I plan to put the plugs in saturday and I want to be right on the gap.. thanks for the help.......its not like the old V-8s I use to work on in the back yard 20 or 30 years ago but every little bit helps..
    bsharles

  2. #2
    Legend

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    Feb 2008
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    Red Wing, Minnesota, United States
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    3,389

    Default

    I am not sure about the gas mileage thing, but I know tha has been allover the site lately about running a smaller GAP, hopefully someone will chime in with some actual real world info on the difference, I have yet to regap
    99 K1500 Suburban LT "THE BEAST"
    Hypertech III, K&N, true dual
    285/75/16
    ___________________________
    Jason

  3. #3

    Default

    Quote Originally Posted by vncj96 View Post
    I am not sure about the gas mileage thing, but I know tha has been allover the site lately about running a smaller GAP, hopefully someone will chime in with some actual real world info on the difference, I have yet to regap
    I've always believed the bigger the spark the more complete the combustion. Once the gap gets too big the plug will misfire however. Also a smaller gap will make your coils live longer. I just set my plugs to factory specs. Spark plugs have always been the most unnecessarily changed part on a vehicle. The reason is most people believe changing your plugs will make your car run better and give you better gas mileage. This is true if your plugs are worn out and your car really needs them. The truth is your computer knows the condition of your plugs by the feedback from the O2 sensors and adjusts the mixture accordingly. In defense changing plugs makes you feel better and the better you feel the better your truck runs.

    Jim

    2004 SILVERADO 2500HD LS
    Pro Comp Leveling Kit
    285-75-16 Cooper ST All Terrains
    Pro Comp Programmer
    Bilstein Shocks
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    Other rides:

    1967 Landcruiser <350 Chevy>
    1970 Camaro
    1990 Geo Metro Convertible
    2007 FJ Cruiser

  4. #4
    Jr. Engineer
    Join Date
    Feb 2007
    Location
    Edmonton, Alberta, Canada
    Posts
    298

    Default

    ^^ hear here.

    I agree completely.

    I went so far to believe that larger plug gap helps out with exploding the fuel better that I put in a full msd ignition and gapped my plugs at max range .075 and I haven't looked back in over 50,000 kms.

    no problems here. HOWERVER this isn't true for all motors. I have spent considerable time working on my vehicles and playing around with gap. I ran my 93 350TBI at .055 before the ignition and then went up .005 many times over the next few months to test it. I found that what I have works for me. you have to play with it to find out.

    I believe you have vortec in there. so you should be able to hook up a scanner if you want that runs live data, take it for a spin and watch your spark advance. (ODBSCANTOOLII is what I use) this will tell you a little about where your motor is running, and where your spark advance is. this has a little to do with o2 sensors, tpi, map and so on.

    sorry im rambling, but starting with playing with spark is a great place to start playing.

    sorry forgot this, if you want better mileage, I am pretty sure that anything you would get by playing with spark wouldn't be too noticeable in the wallet either way. If you want the best mileage you can get, you need to keep the truck mostly factory (except maybe a tune) and keep tires, fluids and filters all up to spec and changed regularily. This is the best way to ensure your mileage.
    Last edited by L0sts0ul; 08-07-2009 at 10:15 AM. Reason: forgot mileage stuff

    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"

  5. #5
    Jr. Apprentice bsharles's Avatar
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    Jul 2009
    Location
    Humble, Texas
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    Default Which plug is best? Ac delco or splitfire ?

    I bought splitfire plugs [copper classic] so should I take them back and get the ac delco? do they work better? and what is SEAFOAM? I haven't heard of it but will look it up in just a minute, I'll clean the TB and replace the pcv and air filter also, I have the 5.7 vortec 350 so it doesn't have a distributor or rotor, And where do I find the Idle Air Control ? sorry for so many questions but I haven't work on a vehicle in years except for the motorcycle I wrecked lol
    Last edited by bsharles; 08-07-2009 at 04:23 PM. Reason: tried to copy and paste ..it didnt work

  6. #6

    Default

    i just use auto lite plugs no need for expensive plugs but go with good wires

    2003 Z71 Silverado LS
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    Waiting to be installed
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