I noticed there is a rattle from what seem to be the tappets / rockers (top part of engine) is this norm? Could it indicate oil change needed as it gets worse when the engine is warm?
They do bleed down, so on start up can initally be a little noisey. Depending on millage and driving use, you could use a thicker oil, eg Mobil1 15/50 which is recommended for track time and race motors; I always run this.
