if yours is intermittant, then i suggest changing your
oil to mobil 1 15/50.
i have had huge success with this.
my shop uses mobil 1 15/50 almost in every car.
if after changing and the noise returns, then change
again. absolutely works.
but if you have some mileage on your engine, i would
suggest you check you cams and rockers for wear and
make sure that the oiler tube plastic connectors are tight.