Question about 2000 Chevrolet Silverado

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Valve train tapping?

6.0l LQ4 sitting in a 2000 Chevy Silverado 2500. Now, here's the problem.

It's tapping only under at least 1/4th throttle and while accelerating the vehicle. When the engine is pushed to the full throttle mark, it's totally in audible and seems like the tap just disappears. Also, when in gear holding the breaks it will no tap even while trying to pull itself.

The engine uses hydraulic lifters with non-adjustable rocker arms. So, this system shouldn't be tapping at all. I've narrowed it down to a few problems here but have no idea where to start looking.

- Bad Lifter?
- Bent Pushrod?
- Bent Valve?
- Weak Valve Spring?

It can't be many things tapping like this, as it's clearly a tap of a smaller metal to metal sound. It really badly sounds like tapping rocker arms in a 2.0 I4 or something. It's notable increase with RPM and throttle noticeable as well.

Anyone have any experience with these engines? Or the 350 5.7l as it's using the same type of valve train? Should I pull the heads first so I can have a look at everything or would it be a wasted trip of 2 head gaskets?

I hope someone can assist me on this.

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The 6.0 engine had an issue with piston to bore clearances, from the factory these clearances were excessive. It is reffered to as "piston slap". This condition is known by GM, but most dealers say it's normal. It can be as slight as an annoying tick, to a clearly audible clacking noise. Unfortunately the condition was under played by GM, and there are many folks who haven't been able to get help with their trucks. I own an '03 Silverado w/6.0, and hear this noise everytime I start my truck. I deal with it, because I'm a mechanic and figure I'll be able to fix it if I need to. Research more online about this condition. I've found many websites that relate to this issue (Google: 6.0 piston slap) I hope this helps.

Posted on Nov 19, 2008


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Posted on Jan 02, 2017

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SOURCE: Rocker arm and pushrod have a gap of about a quarter inch, noisy,

you might want to try tapping it back in, but only if you got a brass drift as that will not mare the stud or threads. back in the day i would drill and pin each one to keep them from pulling out. as this was a commen problem with early ford and chevy high R.P.M. engines. that went away when someone invented the screw in stud. but you can drill and pin each one with out pulling off the heads it can be a chore but its a cheep fix compaired to the alternative. also did you replace the lifters? i ask this because if one was stuck maybe the rest will stick too. i am a chevy person, but i am a little parcel to fords as thats what i had in the day a 1967 fastback 289 4 speed. hope this helps.

Posted on Jan 08, 2009

  • 5158 Answers

SOURCE: falling loose pushrod inside 350 chevy engine 1992

you don't really have much choice but to disassemble the motor, or at the least remove the oil pan, the push rod should be in there. if you see any part of the pushrod from the top try using a magnet to retrieve it.

Posted on Sep 02, 2009

  • 106 Answers

SOURCE: bent pushrod

If it is a push rod or a loose rocker arm it wouldnt be rattling it would be ticking or knoking.

Posted on Nov 17, 2009

  • 152 Answers

SOURCE: it was backfire'n thru carb i removed valve cover

It is probably still getting oil, but if it is not moving as much as the other exhuast rockers chances are the cam shaft lobe for that valve is wearing away.

Same thing happened to me. As it turns out the EPA mandated that most of the anti-wear (zinc and phosphorus) additives be removed from most motor oils. This is because of emissions and because thier presence can damage the catalytic converter. Diesel oils still have all of the additives. I have been putting at least one quart of shell rotella-T into every vehicle we own. Running pure Rotella-T in the one I just put the cam in for now.

Posted on Dec 23, 2009

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SOURCE: I have a 1999 Buick Century V6 3100 that I had to

If the engine oil was full of antifreeze when the intake gasket went bad, then there is a good chance that there may be some cam and/or lifter damage. A more likely cause of your problem would be that the push rods got mixed up when you put it back together. The intake and exhaust rods are different lengths. If this is the case, and you have turned the engine over, there is a good chance that you now also have a bent pushrod and intake valve. The exhaust pushrod is the longer one and if you mix them up, the piston will contact the intake valve because it will not be able to close due to the longer pushrod. This will bend or break the pushrod and bend the valve stem.

Posted on Jan 16, 2011

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