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2002 gmc envoy_slt
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I've looked everywhere for any info on this. Are these valves actually adjustable? If so, is a shim bucket style? Thanks for any info. c good
 

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2004 gmc
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Define "everywhere."

The shop manual? ;)

Anyway, we, along with almost every modern engine, uses hydraulic lifters. No adjustment. I haven't manually adjusted a valve EVER in 35 years except on motorcycles.
 

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Hey Roadie! Yup...Everywhere. Did a Google search, bought a cheap Haynes Mnaual. Couldn't find anything about valve adjustment. Didn't even see anything about hydraulic lifters in the places I looked. Was hoping they were adjustable as I have a small "Tic, Tic, Tic" sound in the very top front end of motor. Normally I would suspect excessive valve clearance with this type of sound. Hmm, hope it is nothing more serious.
 

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Your small "tic" could be a noisy fuel injector. Also under certain conditions the fan clutch can make a ticking noise.

I'm with Roadie, I haven't adjusted valves on an engine since the 70's.
 

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no adjustments since my 1974 superbeetle. My 300zx had noisy lifters. No way to correct that other than using a thicker oil. I never noticed it when I was using 20w50 oil, but heard what everyone else was talking about when i used 10w30. Fuel injectors can make a click as stated already. Usually softer sound though.
 

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I've looked everywhere for any info on this. Are these valves actually adjustable? If so, is a shim bucket style? Thanks for any info. c good
Hello, I know these posts are very old but maybe my 26 yrs experience as a diesel mechanic may help with this question. I have also looked for a valve clearence spec but to no luck. As a diesel engine builder, I have worked with overhead cams for many yrs. Every one of the have some kind of spec. In the diesel world, when valve adjustments are needed because the valve clearence closes. Thats right, closes. The valves stretch to close the gap. So applying this, the 4.2 may use this to its advantage and that is why there is no spec that anyone can find. If there is a tick it is a worn cam lobe or follower.
 

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@ c good, --- YOUR: Hey Roadie! Yup...Everywhere. Did a Google search, bought a cheap Haynes Mnaual. (sic) Couldn't find anything about valve adjustment.

Did you have help getting that Haynes Un-Manual out from under the short piano leg?

That's where Haynes Manuals belong - shoring up a short leg on a table, piano or a bed headboard.
 

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Hello, I know these posts are very old but maybe my 26 yrs experience as a diesel mechanic may help with this question. I have also looked for a valve clearence spec but to no luck. As a diesel engine builder, I have worked with overhead cams for many yrs. Every one of the have some kind of spec. In the diesel world, when valve adjustments are needed because the valve clearence closes. Thats right, closes. The valves stretch to close the gap. So applying this, the 4.2 may use this to its advantage and that is why there is no spec that anyone can find. If there is a tick it is a worn cam lobe or follower.
I too am an old diesel mechanic - US Navy and on into civilian life in my own shops and garages, etc.

Roller lifters are a different dog all together.... like a Detroit -71 series or any other modern engines and they tend to never wear out a cam lob.

Rollers MAY fail - but they do much more than 'tic' or 'clatter'. .

Beside valve stem stretching - the seats can drop as the valves themselves can tulip - but that's really in extreme RPM and/or excessive heat situations and with poor alloys, etc. I cannot say I've seen any of those situations in many many years either.

Stem stretching can be caused by very high spring pressures too. ... just sayin'....................
 
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