Engine tapping until up to temp ?
 

2005 Bonneville sle L36 3.8
I am getting a tapping sound that varies with rpm up to about 2200 that happens until the car reaches operating temp. I removed the belt to make sure not HB or any other pulley and still there. Again, the sound completely diminishes when at operating temp. Doesnt sound like a lower end knock or bearing. Could this be a bad lifter? Or loose rocker arm? If anyone has experienced this or could give some input that would be great. Thank you

valve train noise?

How many miles on it?

How many miles on the current engine oil and filter?

The car has 228K on it and has always been maintained. Recently changed the oil and have always changed it at around 3500 to 4000 miles using full synthetic mobil 1 5w 30. Its definitely valve train related but strange that it 100% goes away when fully warmed up

If its valve train related, why not do an overhead valve adjustment?