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Thread: Rod knock?

  1. #1
    Junior Member SHOW GUEST
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    Rod knock?

    :evil: Maybe this post should be in the angry venting category...???

    So I was helping troubleshoot a SBC problem over the phone Sunday evening. Sure sounded like a rod knocking - but it was over the phone... I wanted them to check the valves but they were going to pull the engine instead.

    Today the knock was quieter and then went away after revving the engine a little bit???

    Now I hear it's running fine and that they did check the valves - one lifter was stuck up??? I call BS! The engine would be backfiring one way or another if the valve was open. How can a lifter get stuck upward after doing a carburetor swap?

    Anyone hear of knocking "going away" the next day?
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  2. #2
    I come across this all the time with people not used to forged pistons, and complain when the engine is cold, but after is is warmed up, noise goes away

  3. #3
    Senior Member RACING JUNKIE
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    does it have mechanical fuel pump?? push rod could have been sticking in bore a little knocking the cam

  4. #4
    Senior Member RACING JUNKIE
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    Is it a solid lifter motor? I hear some lifter noise/knocking occasionally when they are cold or loading up some... they can be noisey...

    Tough to tell on the phone too...
    "I would walk through hell on Sunday before I fear the enemy"

  5. #5
    Senior Member MASTER BUILDER
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    Noise after a carb swap,something might have fell into the intake.Hope not. Bill.

  6. #6
    Senior Member DYNO OPERATOR
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    I changed rocker arms on my Pontiac years ago and broke a crank, haha. Ran better than ever.

  7. #7
    Junior Member SHOW GUEST
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    It's a stock 350, cast pistons, hydraulic lifters. It does have a mechanical fuel pump... Never heard one stick before.

    Over the phone this thing was thumping pretty hard. They said the sound seemed to come from down in the center of the engine.

    Who knows??? :?
    : G r a n i t e . C i t y . P e r f o r m a n c e :
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  8. #8
    Senior Member RACING JUNKIE
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    mechanical fuel pump. i had a new pump arm stick and not return fast enough and knock against the cam and sounds like a rod knock that can come and go. push rod for pump could be binding in its bore and do the same.

  9. #9
    Junior Member SHOW GUEST
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    flexplate?

  10. #10
    Senior Member RACING JUNKIE THERATTLER's Avatar
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    I have heard a terrible knock in a chevy 350 in a corvette..it was carbon on top of piston , sounded just like a rod...poured trans fluid in carb with engine revved up to break it loose , knock went away , still running today..
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