The valve gaps are measured between the "slipper" on the rocker and the back of the cam lobe (not the lifting part of the lobe).  I just rotate the engine as necessary to get the lobe facing away from the rocker - 0.012" (0.30mm) inlet, 0.014" (0.35mm) exhaust.

The cam shaft lobes are lubricated by oil that is sprayed from little holes at the base of each rocker.  The problem with the Gamma flat four is that the oil in the cam chamber drains back to the sump when the engine is not running and over time the lobes can loose the oil film protection.  It takes 3 - 5 seconds for oil pressure to build up at start-up and re-establish the oil film through the rocker spray holes.  So, if a long period has elapsed since the engine was last run, it is good practise to disconect the HT lead from the dizzy and turn the engine over on the starter motor until the oil pressure warning light goes out.  This re-lubricates the cam lobes and the HT lead can then be replaced and the engine started.  It is also recommended to use fully synthetic oil as the film strength is stronger (even though the oil seems thinner) although I generall use a good quality semi-synthetic for "classic" engines.
Of course, the real answer is to use your Gamma regularly!

hi all as you are aware I'm in the middle of a pair of head replacements and noticed one of my camshaft lobes had worn quite badly so I've replaced the shaft   but i can  see the cam rotating shaft is lubricated by engine oil pressure via small holes but can see nothing for the lobes so do the rely on oil spray ect?

thanks to everyone who has helped with this little problem i had well heads are ready gaskets on the way so onto valve clearance when i refit heads as I've read the rule of 9 does not work so i would guess clearance is checked between cam lobe and rocker arm and not rocker arm and valve and possibly on the lowest part of the cam i.e. opposite the lobe lift  end is this correct or is there a cunning way to do this?
thanks again

Hi Neromoto yes as i had to send the head to my machine shop for a new valve seat to be fitted they confirmed it has 9mm valves   so should be later series 2 valves thanks for all the advise it really helps.

If you are replacing a new intake or exhaust valve, check the stem diameter.
S1 and S2 have different stem diameters.

hi thanks for that i think where i have misunderstood s1 s2 heads is the picture above shows a series 2 head but at glance it looked different to mine but looking again it still has the gasket attached so blocks off some holes, also the fresh air holes on series 1 heads  do i need to block these off on mine i assume not as the heads  that came off were not blocked and it all seemed ok.

I think where I've misunderstood about the heads is the picture of the head above which is a series 2 must still have the old gasket attached as i can see more cooling holes in my head than i can see on that so thats why i thought they differed by the way the fresh air ports for s1 heads should i block these off on my series 2 or does it not matter as they were not blocked on the heads that came off.
thanks
Keri

Keri,
The heads are the same it is just the gasket
that was updated with aids to cooling flow

  thanks for the pictures of the head and gaskets but to confirm is the picture of the head defo series 2 as it has less cooling holes in it than the 4 heads i have here so I've assumed the series 2 head has more cooling holes than early head? and also the gaskets that came of mine are the same as the ones out of the packets on the pictures with more holes so are these gaskets series one or two just so i can order the correct ones.
thanks again for all your help