The jag head is a straightforward 2 valve head, apart from the number of cylinders these are straightforward to work with.
The design is simple: a single cam drives a line of valves mounted vertically via bucket tappets. Valve clearance is set by a shim between the tappet and the valve stem. Setting clearance involves measuring observed clearance and replacing shim as required.I removed the tappet blocks to allow access to the cylinder head securing bolts. One flaw in the design of the V12 is this requirement: everything would be so much easier if the head bolts could be reached more easily.
Nothing unusual was found, combustion chambers are a little coked-up but otherwise there is low corrosion and no other obvious problem. Important to keep tappets in order...Valves were cruddy but generally fine. one of the intake valves showed radial cracking, so i replaced the whole set with new ones (as inlet valve sets come up regularly on eBay....but no exhausts...)
Heads were sent for skimming by a local company here in Malaysia, new bronze valve guides were fitted.