do i need a oil pump

Here is a test: rev up the engine when it's warm, than stop it and pull the dipstick out. If you see small air bubbles in the oil, it means the pump loose and the oil gets aerated. Since air can be compressed the hydr. lifters can't work properly. Sometimes the oil pump's bolts gets loose completely and hit the pan. You need to remove the oil pan and check. Clean the bolts and apply blue thread lock, it should hold them in place in the future. Zee

no you do not need an oil pump, if you did your engine would have froze up long ago due to no lubrication. you need a valve adjusment