tick/rattle from engine under load

Discussion in 'Engine Topic' started by woody80z28, Oct 20, 2011.

  1. woody80z28

    woody80z28 Veteran Member Lifetime Gold Member

    5,308
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    Sep 8, 2004
    walton, ny usa
    The 357 I just built has a tick/rattle that you can hear under load and I can't figure it out. The best way I can think to describe it is "diesel-like" in sound. At idle and past about 2500rpm you can't hear it.

    It's not spark knock, I've checked the knock sensor with a hammer and it works, and pulling timing didn't help.

    I thought maybe it was from the small weld pinhole in my fabbed exhaust (which is the only leak I could find) and fixed that last night with no change in sound.

    Oil pressure & level is good. 80psi cold and about 40 warm at idle according to the stock gauge.

    Could it be a lifter or something mechanical? The engine has less than 150 miles on it so far. I converted the engine to an OE-roller setup and adjusted the lash a half turn past the pushrod spinning by hand (same as I have done with my other SBC).

    It runs well, but just doesn't sound normal.
     
  2. Pfrederiksen

    Pfrederiksen Veteran Member

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    Feb 21, 2011
    Edmonton,Canada
  3. woody80z28

    woody80z28 Veteran Member Lifetime Gold Member

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    Sep 8, 2004
    walton, ny usa
    Nope. Stock LT1 F-body cam.
     
  4. woody80z28

    woody80z28 Veteran Member Lifetime Gold Member

    5,308
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    Sep 8, 2004
    walton, ny usa
    Uh oh.

    Decided to check my valve lash and I could spin the pushrods by hand. So I tightened them until they stopped spinning (maybe 1/8 turn) and gave them a half turn of preload. Went back through to double check and they all could spin by hand again. So I gave them another half turn. Went to start the engine and it wouldn't fire.

    So I backed them all off and adjusted them opposite of the open valve like I always do and must have missed one in a hurry. Sounded like the engine ran on 7. So I went through and did them all one by one adjusting them just a little after valve closing.

    Now it sounds like I have one distinct lifter tick. Did I collapse a lifter running it with too much preload?

    And - the original sound is still there.
     
  5. Pfrederiksen

    Pfrederiksen Veteran Member

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    Feb 21, 2011
    Edmonton,Canada
    Adjust them with the motor warmed and running.

    P
     
  6. phbmd

    phbmd Veteran Member

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    Feb 11, 2008
    Olney, MD
    I hope you fix your problem with some simple upper valve train tuning.

    But I always remember a friend's 400 T/A that started running a little weak and made a tapping/clackety sound when he got on it....his turned out to be a broken cam lobe. Hope yours is simpler, but I thought I'd share it.
     
  7. woody80z28

    woody80z28 Veteran Member Lifetime Gold Member

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    Sep 8, 2004
    walton, ny usa
    The lifters were used out of a salvage L31 Vortec engine. Maybe I'll just pull the intake and drop in a brand new set to rule it out.
     
  8. woody80z28

    woody80z28 Veteran Member Lifetime Gold Member

    5,308
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    Sep 8, 2004
    walton, ny usa
    Can a collapsed and/or otherwise noisy lifter straighten itself out? The distinct lifter tick I was hearing has gone away and the engine is running great. I bought lifters, but I'm wondering if I really need to swap them in.
     
  9. middleagecrisis

    middleagecrisis Veteran Member

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    Oct 22, 2007
    SA, TX
    If the motor is running good, I'd chalk it off to the lifters being out of adjustment and run it as-is.
     
  10. Air_Adam

    Air_Adam Veteran Member

    This is outta left field maybe, but I've heard it in alot of mid-90s and newer 350/LT1/LS engines with a stock bottom end... are you maybe hearing some piston slap? Does it change with temperature? I've heard a few stock, untouched LS1 engines that had some wicked piston slap when cold, that would mostly (but not entirely) go away when warmed up. GM called it normal, and I've never heard of any problems that came from it. My '97 LT1 did it a very little bit too when cold (usually up to around the temp the guage would start to read), and it never caused me any problems either. It fits the 'diesel-like sound' description.. especially the LS engines lol.

    What bottom end is in your motor?
     
    Last edited: Oct 26, 2011

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