I guess the question I have is, does the housing-with-compressible-gasket have to come off to adjust the valves? Is there not some special tool to depress buckets and pop out shims? EDIT: I guess from diameter measurement that the shims are under the tappets... oh dear.
When I built my SOHC 1498cc engine for my 128 coupe, you could possibly have said the same thing - the cam housing had a gasket where it bolted to the head (pictured) - the paper gasket leaked at the front corner so I replaced it with something rubbery of unknown thickness. Plus, I had about 1.5mm taken off the cam housing base as a 'seat of the pants' judgement based on the reduced base circle reground cam I was going to use; I guessed that I wanted to use thinner shims rather than thicker.
This is when everything taken everything apart again after the head gasket blew (second pic), maybe the 10.8:1 compression wasn't such a great idea.
But the point is that the gasket thickness didn't matter because valves could be adjusted easily after the housing is torqued down - tappets depressed with special tool A60421 (how I remember that, long story as I broke the only one belonging to the specialist and had to get a replacement) - not so easy when cam too close to buckets as a result of 1.5mm off the housing (that's why the tool broke), but anyway. Because we have all been saving these 'coins' since we were little boys, it's just a matter of swapping them from a supply of, oh, about a hundred, to correct measured clearances (so, gasket not an issue for the FIAT engine, and milling - no way!
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That's the FIAT engine as in 128, X1/9, Uno, Tipo, Punto etc. There must be 15 million cars out there with that motor... Our original 1969 128 saloon had the earliest 1116cc type, while a close friend has a 1995 Punto 90 (1580cc MPI version) which is perhaps the last of the type. My personal favourite is the 1301cc small-bore version in my Uno Turbo.
I think it was just as well that I learned on simple engines like the FIAT's, at least parts were plentiful when I broke things! Third pic shows shims being removed from Uno 1301cc 'big-bore' non-turbo engine. With 14psi boost in my Uno Turbo, I think you can see why I'm happy for the head gasket to have the bores a little further apart.
I'm still trying to get my head around how to adjust inlet valve clearances on the Alfa V6, so maybe the Maserati is just too difficult for me to comprehend...
It seems a pity that the design genius of the FIAT SOHC and DOHC engines, in terms of serviceability and durability, could not be scaled-up to the performance engines...
-Alex