I've dug up this thread because I had exactly the same question. Some of my tappets had ruined surfaces (craters starting in the centre), some had random chip-marks (but smooth-feeling surfaces) and some had blue-ish rings as though the tappet had been rotating very, very fast...
The cams still look in good condition without evidence of rounding or rapid wear. My theory is that disintegrating tappet surfaces cause the cam wear that seems to be common in these engines, rather than the other way around.
So, I grabbed a handful of tappets from a spare 2.0TS cylinder head (not mine, I had to make a two-hour return visit to a specialist). All had excellent condition surfaces.
I was in the process of fitting them when I noticed that most of them are 'squashy'. Tappets from my engine are not squashy (I can push in the 'piston' (cone-shaped piece), which squirts oil out, and then the piston stays in until I pull it out).
Three of the replacements are not squashy - they can't be pushed in at all, or pulled out - they seem to be 'stuck'. I sharpened the tip of a butane aerosol can and tried pressurising the oil hole - liquid/gas shot out from around the piston but still the piston did not move.
My question was going to be whether it is OK to use the six squashy tappets that do push in - I've left them soaking in kerosene and also tried pushing them while soaking - I can get all the air bubbles out (so, the squashiness is not caused by air!) and then I get little jets of kerosene from the oil holes, so that suggests they are serviceable.
Then, I found Smaky's brilliant photos of a sectioned tappet: http://www.alfaowner.com/Forum/attac...-pics-043a.jpg
This shows there is a spring inside! Therefore, the 'squashy' feeling must be normal. My guess is that the spring was eliminated in the newer tappets, perhaps because the spring breaks and jams the tappet?
It would be nice to buy a complete set of new tappets, but this is the end of a huge project for me and I literally have no money left
So, I'm going to use the six squashy tappets on the exhaust valves, the three that don't squash, I won't use at all as I think they are jammed, and the remaining 10 tappets are from my engine - they don't squash but they do push-and-pull.
Still, I thought this was worth mentioning and asking about, since I think the 'dead' ones are the ones that aren't squashy - it appears that some tappets are meant to be squashy, and others are meant to be free to push/pull.