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Engine has knock when cold

This is a discussion on Engine has knock when cold within the Internal Engine forums, part of the LSx Technical Help Section category; I just picked up this 2000 SS Camaro a week and a half ago. When engine is cold, it has ...

  1. #1
    TunedByFrost supporter rel3rd's Avatar
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    Cranberry Red
    1971 Chevelle SS 402

    Question Engine has knock when cold

    I just picked up this 2000 SS Camaro a week and a half ago.

    When engine is cold, it has a noticeable "knock" that sounds like a rod knock. It is definitely NOT a valve tap...it sounds much deeper.

    When engine is warmed up, the noise is all but non-existent.

    Oil pressure reads 60psi at light throttle cruise
    Just shy of 40psi at warm idle
    50psi at cold idle.

    Original owner said he used Mobil1 only.
    Engine has 110,000 miles but runs fantastic.

    If you rev the engine up, noise is gone...or at least I cannot hear it then.

    I tried SEARCH function here and elsewhere and most engine knocks seem to be when HOT, not when COLD....

    Any ideas?
    2002 Silverado Z71 ECSB HPTuners tuned by yours truly
    2000 Pontiac Trans Am WS6 6.0, 4L80E, Rear mount Turbo, etc...
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    Member danziger's Avatar
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    Le Mans Blue
    2004 Z16

    Probably the pistons banging around until the warm up and expand. This is commonly called "piston slap". The good news is that your goes away upon warm-up. Keep a close eye on oil consumption...

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    Simpsons Did it!! 98formy's Avatar
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    83 Z28 new project
    98 Formula WS7-sold:(

    I have a 98 and it does the same thing. It gets really noticeable when its 5 below zero.

  4. #4
    TunedByFrost supporter rel3rd's Avatar
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    Cranberry Red
    1971 Chevelle SS 402

    Quote Originally Posted by danziger View Post
    Probably the pistons banging around until the warm up and expand. This is commonly called "piston slap". The good news is that your goes away upon warm-up. Keep a close eye on oil consumption...
    So far, so good on the oil...of course I haven't driven it all too far or long yet...

  5. #5
    I lika da Chevy's LETHALxLS1's Avatar
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    Mine has the slappy slappy too untill she gets warm. It eats no oil. Just start it and go back inside the house for 5 minutes LOL thats what I do.

  6. #6
    TunedByFrost supporter rel3rd's Avatar
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    Cranberry Red
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    Quote Originally Posted by BREAKxNECKxSPEED View Post
    Mine has the slappy slappy too untill she gets warm. It eats no oil. Just start it and go back inside the house for 5 minutes LOL thats what I do.
    Never thought of that, lol...

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    Member danziger's Avatar
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    Le Mans Blue
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    You could try using different brands/weights of oil and see if any reduce the slap, but I doubt it. Short-skirt pistons, long-ish rods and low tension rings are the culprits...

  8. #8
    TunedByFrost supporter rel3rd's Avatar
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    Cranberry Red
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    I plan to try that soon. I drove it to work this morning...loud as heck when I first started it, quiet as a mouse 5 minutes later....weird...

  9. #9
    Member danziger's Avatar
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    Le Mans Blue
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    Yah. Once the pistons warm up and expand, there is no room in the bore for them to rock and slap. I had some decent slap in my old 5.0 GT, but it never caused any issues...

  10. #10
    TunedByFrost supporter rel3rd's Avatar
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    Cranberry Red
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    I feel much better about it now, thanks to all the feedback and after Google-ing the heck out of "piston slap", lol.

    When I first looked at the car, it had just been parked, so it was already warm. I drove it, loved it, and bought it, and the next time I saw it was a few hours later when they delivered it to my house (so they could get their tags off the car).

    It was definitely a bit un-nerving when I first started it cold , and of course I thought the worst since I didn't know about the knock problem alot of these LS1's evidently have.

    No regrets at all though...
    Bought an 89 LX coupe about 2 years ago for $2500
    Fixed it up a bit and sold it a year later for $5500
    Took that $5500 and bought an 85 Vette.
    Sold that a few weeks ago for what amounted to $8000
    Then bought my first LS1 car...

    I thought my $2500 SS needed an engine...but now that I know different, it's all the better.

  11. #11
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    black
    1969 camaro

    Allright guys, heres the deal.. the noise is carbon buildup on the top of the pistons. You can pull the plugs and pour old school carb cleaner in the holes, let it eat for an hour, then turn over the motor( and yes... make a mess), emptying the cylinders. Install the plugs and fire it up. the noise will be taken care of for about 20k miles. oh and change the oil too.
    I am shop foreman for a gmc dealer and have run across this many times. the noise will not hurt anything. GM considers it normal, something to due with no skirt pistons and carbon build-up. The only thing I can Gaurantee is that it will return.

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    I lika da Chevy's LETHALxLS1's Avatar
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    you think sea foam will fix it??

  13. #13
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    black
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    not familiar w/ sea foam, anything that eatscarbon will work, superclean wil eat the carbon but you would have to washit out w/ water and that promotes rust... use the carb cleaner undiluted.

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