I understand the parts present and what they look like under the SOHC I6 from when I did the gasket change. however..What are the difference between rocker arms/tappets, hydraulic lash adjusters, what makes that tapping sound you don't wan't to hear etc. I'm suspect multipple names are sometimes used for 1 item. Does any1 know a site that gives a brief overview of the different components under the rocker cover?

Here is a pic with a rocker arm, a hydraulic lash adjuster (also called tappets/lifters) and a shim (the coin looking thing in the middle).



Both the HLA and the shim sit in the hole at the end of the rocker arm and push down on the valve. Its the job of the HLA to pump up with oil and take up slack between the rocker arm and the valve. When the HLA gets old (gunked up with carbon) they dont open up fully and the rocker arm bounces on top of the valve making the ticking sound. Cleaning or putting new HLA's in let them pump up and keep tension on the valve so no ticking.

This is also why some people get ticking after installing a regrind cam. When the cam is reground with a new profile the distance between the rocker and the valve is increased to a point where the HLA cant pump up with oil to bridge the gap. To get around this you add extra shims which pushed the HLA closer to the valve in the rocker gear. If not enough shims are added, the HLA still will have a gap and it will tick (if too many are added the HLA will force the valve open all the time which is bad as well).

ahh, awesome. Jesus mate, your so helpful all the time, when I start earning good money, I swear i'm buying you a present.