Understanding Subaru Valve Lash "Shim" Numbering?
 

I'm trying to set the valve clearance on a 2013 FA20 engine,.........does anyone have a listing that gives actual shim thickness (preferably in imperial), that can be associated with the numbering system that Subaru is using to ID their shims? This has got to be the most confusing deal I've run into in a LONG time! The numbers that are etched onto the shims don't seem to relate to an actual thickness, but in the part # specs for a "1.94" shim indicate that is "T",.....which I would assume "T" would be the thickness of the shim. I measured the shim an the thickness measures aprox. .0024"! 1.94mm equals .076",.............I'm TOTALLY not understanding what the number that is etched on the shim means?
On a second note, it seems to me that I saw someware that there are OEM rockers available that have added/reduced clearance, to help get you back in the "range" of available shims, after having cylinder heads remachined. Does anyone have info on these rockers?

The numbers on the shim are the size in mm. So the 194 is a 1.94mm shim. The actual size needed is a bit trickier due to the rocker ratio making the clearance different. There is a formula in the service manual to calculate the correct shim size.
There are 2 different rocker designs. Early engines have valves about 5mm shorter than later engines which require a different rocker. They are not interchangeable, the difference is to much.
It is possible to shorten the rocker pivots to create more clearance. This is best avoided unless you know exactly what you're doing! If your heads are unmodified shims should be available to get it right.
It is also possible to machine the top of the shims to get some more clearance. Again, not recommended but if you know what you're doing and you're desperate it can get you out of a bind.

I know this is old but in case anyone is stuck on it:

Measure and calculate the desired shim thickness per service manual as mentioned above (have conversion to mm and in, I can’t remember which was used).
Call up the best Subaru/Toyota parts counter in your area and walk through all the shims you need by thickness - they can give you the corresponding part number. It’s frustrating that the thickness is not just in the part name but not much we can do about it.

As a note, I was surprised that about half my shims were borderline too loose after 117k miles, one pair was out iirc, worth putting in the effort if you’re hunting for those last tenths of a pony. Injector cleaning was probably worth more though.

I'm surprised the gap was "loose". With wear, I would think that recession of the valve would have decreased the lash.