the shim sits in the rocker arm. initially the point might be to provide a base for the HLA's to sit on and control oil flow i assume.

in regrind cams they are used to offset the amount ground off the cam so the rockers/HLA's are still in contact with the valves and cam at all times.

Ive got a reground cam........its got washers holding up the HLA's, as installed by Jaysen, its run perfectly for the past 30,000k's...........and I'm quite confident for the rest of the motor's life.

Cheap as chips, never given me and issues (only one being, they take a while to fill with oil.......and as a result make a noise when i start the car, if noises dont bother you, then howabout some washers?)

One other thing..........you can't really assume that if one person used 1 shim, that you will get by with the same (even if it is same cam/same model car).........me and Sir Kezz run the same cam, same rocker gear/motor (untill Jay gave me EF rocker gear), one of us has more shims (cant remember, it doesn't really worry me) Jay checked out the clearancing of the rockers, and from there, determined what to use.

Did this over a year ago, and don't really remember correctly, but im almost 100% certain on both the use of washers in my car, and that me and Kezz have different amount of shims. (If Jaysen comes on and corrects me, then yea, I was wrong, but it was ages ago )