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My engine!! ARG!

Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by 72K5BEAST, Dec 28, 2001.

  1. 72K5BEAST

    72K5BEAST Registered Member

    Joined:
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    Location:
    Oklahoma
    Well here's the scoop, almost every time I turn my engine off...<CLANK><PSHHH><Boom><Clank>... it just sputters up a storm. Now, i've heard this could be timing. I'm open to any other ideas about what it could be and would greatly appreciate the help. Keep Blazin everyone.
     
  2. Steve_Chin

    Steve_Chin 1/2 ton status

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    Location:
    Foster City, CA, USA
    This is a condition known as "run-on" or "dieseling." It has nothing to do with ignition timing since when you turn off the key, there is no more spark. It is always related to carbon deposits in the combustion chambers causing hot spots, igniting the F/A mixture upon compression. These carbon deposits could be due to many things, primarily to low-speed carburetor calibration. Without seeing your setup, I could only guess that you probably have an overly-rich idle mixture and a throttle blade opening that is too large at idle. Couple that with too much main jet, and you're creating carbon deposits and providing the engine with a lot of fuel and air after iut is shut off.

    I would suggest that you have an experienced carburetor tuner re-jet your carburetor (if you have a Quadrajet, find someone who has extensive experience with Quadrajets, if it's a Holley, find someone with a lot of experience with that model of Holley). This will ensure proper fuel/air metering. After you do that, get a can of GM Top Cylinder Cleaner. Follow the directions on the can exactly. This will help clean out the carbon deposits and you should no longer have the problem.
     

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