ive got a ej20 import wrx it has a nockin on the o/s head ive had it compresion tested and it readin fine it has all power ive just serviced it and put 5 30 fully synfetic oil in it could that be the cause or does any1 have any ideas

 

hi mate the scooby engine are known for been tappy, is a knock or a tapping noise? is it when cold? warm? or both? is it loud?

could you not get an oil pressure gauge from somewhere oil have the oil pressure tested? if its only when cold could be piston slap?

 

What age is the car mate as the earlier one's take a 10/40,5/30 is abit thin so it could be a tappet clicking.