I recently built a 4.6 stroker out of my 4.0. everything runs great, but around 3000 rpm under load, i get a random tapping noise in the engine. it isnt a knock, and i thought it was the rods on the rockers. i pulled the valve cover off and checked everything out. there is flow through the pushrods and no severe markings on the rockers. this only happens after the eninge is at operating temperature and the oil is warm. i use castrol synthetic 5w-30 in my motor. i think the oil might be too light for the engine. i have 20lbs of pressure at idle, and at 2000rpm im at 40-41lbs. would moving to a 40 weight oil help with this? i know it isnt damaging anything yet, but the wear on the rockers could lead to premature failure. i also just moved to upstate NY and i dont want to go too heavy. would a lucas oil additive be a better choice? thanks for the help guys, I need all i can get!