Keith,
In general lifters come in two design types: solid and hydraulic.
A solid lifter is just that and requires periodic adjustment called valve lash. It can be a roller type with a ‘wheel’ on the bottom that rides on the cam - or - a solid cylinder. Even when correctly adjusted you still hear the ‘tic tic tic’ of the valve train. Its more exaggerated if one is out of adjustment (too much play) and you get tic TIC tic. Too tight and you may get a rough running engine as the valve will not seat properly and eventually ruin the valve / seat.
Hydraulic lifters have been around for a long time and in wide production since the 60s. They really are a marvel of engineering. They are, quite literally, a small piston and cylinder with an internal spring. As they operate, they pump oil up thru the pushrod and supply oil to the rocker mechanism. And they too come in a roller type (which your engine has) as well as a cylinder (albeit not solid!). The advantage of these is they do not require periodic adjustment and are much quieter than the solid type. Their adjustment is basically a one time, upon install, situation.
If you (not your mechanic) are indeed hearing a tic TIC tic then the rocker stud can be pulling out causing the initial adjustment to no longer be valid, hence why Scott suggests using that straight edge > the tops of the studs should be in line with each other > if one is high, it is pulling out. One way to help narrow down which bank is to use a large screwdriver and place the tip on the engine (while running) and put the other end on your ear. This ‘stethoscope’ process can even help narrow down which cylinder. Just be careful of loose clothing and rotating parts! Also be ready to replace the valve cover gasket when you do this > they should not be reused.
Other potential causes are a failing lifter or even low oil pressure (but that would show in other ways, i.e., oil pressure gauge, lots of the valves TIC'ing, etc.)
Good luck and post how it goes.
