Valves out of Adjustment

Old 01-11-06, 01:03 PM
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Smile Valves out of Adjustment

Have a 77 GMC truck with 250 inline 6. Have set timing according to specs however, once I accelerate to 50 mph the valves begin to start lightly rattling. Is it possible that valves have come out of adjustment? How do I correct this problem. Additionally since the previous owner installed a hot cam and bored the engine .60 over will I continually have problems with this engine regarding timing and valves. I have noticed the engine is using some oil. Can valves out of whack lead to this? All help and advice are greatly appreciated. Thanks for your time
Old 01-11-06, 02:55 PM
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ooo lot's of possibilities here what cam ? what type of lifter ? you should try to get the previous owner to give you some info on what he did. this is just a stab at what i would do. that being said, for starters, check the valve clearance. it they all are less than zero, you most likely have a hydraulic cam and lifter setup. warm it up, loosen untill you hear the rocker clatter, then tighten one turn slowly. this is a baseline adjustment. you need to get some specific information on the setup. if you find that all rockers have "some" clearance and are somewhat consistant, set them at .020" and try that. as far as valve timing, find a chilton's to check the gear/chain installation. don't let anyone talk you into anything involving " degreeing the cam" it's a waste of time with what you're dealing with. just to rule out the possibility toss an oil pressure gauge on it and observe at 50 mph. if the oil system is restricted it would cause valvetrain noise at higher rpm's. let us know how it goes.

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