1988 chevy cheyenne 3500 w/ 350 4 speed tranny. my truck ran fine last night with slight lifter tick like usual-(once it warms up) and today i started truck and instantly started tapping real bad almost a knock. i started to drive and it kept on knocking. i removed valve covers and it looked like there was no oil on the rockers, if there was it was verry little. i started truck back up after that and gave it a little gas and it slowely accelerated like it had no power, unlike before when i hit the gas it would spin tires. anybody have any clues on what it could of been. dipstick looked good on oil, would oil pump failure make all of this happen?