I fitted a 16v Engine into my project car which was running perfectly before i changed it, infact after it ran perfect after too!
I snapped off the spade on the oil sensor while fitting the engine and from the first start the oil light would flash constanty, over 2000 rpm or so it would start beeping.. I presumed it was just the sensor i snapped as oil pressure would cause the tappets to go nuts!
About 3 months later (its been sitting for a while) it just started tapping quite badly, so i changed the sensor (which turned out to be the temp for the MAF) And the oil light is still flashing constantly as well as it tapping
Im worried now, its odd this began when i changed the engine.. The only thing i can think is when i fitted the engine it rested on the front engine mount and sqished the bottom of the oil filter just a little bit, but it ran fine without tapping for a while, im wondering if it just needs a good service and the oil light is electrical problems, but im not going to risk it to find out without asking opinions first.