Just rebuilt my 1.8 zetec and ever since ive restarted it ive been getting a top end knock, sounds to me to be lifters

ive been told by some1 that this shud dissapear after the first oil change, but i dont wanna damage anything during the first 500 miles

im using 10/40 oil atm as i was advised to use non synthetic oil to allow the rings to bed in the bores, cud this be a cause? too thick an oil for the lifters to work correctly????

cheers for any help ppl, much appreciated