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Thread: Newb from Bama

  1. #1

    Default Newb from Bama

    Hey Everybody,

    My name is Mike, I found your forum while researching a slight knock I am dealing with in my '98 K1500 Silverado. Seems as though there is great deal of knowledge and information around here. I am looking forward to utilizing that knowledge to keep my truck rolling down the road. Glad to have found this place and can hopefully I can give some of that knowledge back as I come across it as well.

    Anyway, I am dealing with a slight knock in my 5.7 L 350 vortec. The knock has recently started occuring particularly when the engine is cold at start up. The engine idles perfectly fine but whenever it is put in gear and the throttle applied there is a slight knock that eventually goes away once the engine warms up. Im not sure if this is only a cold weather thing seeing as how this winter is the first it has ever happened. I have read a little on piston slap, as well as watched some videos, the symptoms my truck has don't seem to match that of piston slap, due to the knock only occuring under load. Im really not sure though.

    I had the engine replace about 3 years ago with a crate motor, it has about 40,000 miles on it today. I have never had a problem with until now, if this is a problem.

    I also had an idea that I am running to heavy of an oil. I have recently moved to Central Alabama from North Florida which is a pretty large climate difference when it comes to winters. I am currently running and have run since the new engine was put in Mobil 1 10w-30 full synthetic, so maybe it takes a little more heat for it to get moving.

    Any Thoughts?


  2. #2


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  3. #3


    To the Club!!! How long does it knock when you start it up and how loud is it. I hear a lot of engines especially when sitting for a bit that knock when first started up. sometimes for like a minute. but if your getting down the road with it and under a load here in knocking I think you might have other issues.
    Maybe try some higher Octane fuel in it to see if its detonating. Im sure others will chime in with some suggestions also. Good luck

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  4. #4


    It only knocks for the first few minutes when moving and not at idle, basically knocks until the engine reaches running temp of 160-180, so maybe 5-10 minutes then it completely goes away. Its not a terribly loud knock but definitely enough to notice. It very well could be an octane issue.

  5. #5


    Definitely sounds to me like a viscosity thing to me bud, try a thinner oil during the winter months!

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