97 suburban plug gap

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by bsharles, Aug 7, 2009.

  1. bsharles

    bsharles New Member

    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..
  2. vncj96

    vncj96 Epic Member 5+ Years 1000 Posts

    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
  3. Jimmiee

    Jimmiee Epic Member 5+ Years 1000 Posts

    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. :)

  4. L0sts0ul

    L0sts0ul Rockstar 100 Posts

    ^^ 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: Aug 7, 2009
  5. bsharles

    bsharles New Member

    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: Aug 7, 2009
  6. Z71_guy

    Z71_guy Epic Member 5+ Years 1000 Posts

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

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