my 1997 Chevy Pickup with 350 cid and 110,000 miles taps/ knocks when cold( goes away after a minute or two) and when under hard acceleration. A dose of valvemedic helped the situation for a week or so and then returned. The engine does not burn a drop of oil and still runs like the day I bought it new. Oil pressure is not a problem cold or hot, running >40PSI all the time. Is this a valve/lifter problem or some other sign of catastrophic failure?
Thanks for your help