-Stephen- Above a couple of photos on the last project that my father Julian and myself had been working on together. Being a totally brand new SOHC engine with a works type cam box with enclosed rockers; and yes, you do see alloy rockers (the originals being steel).
The valve stem ends do not enter the cam box but pushers (or tappets) are used. We have copied the cambox as per the one I managed to get hold of and I am under the impression that only 6 of these camboxes were ever produced, plus an initial first off which looks a little different. The first off never had enough room for the valve lift used by the works racers and is in Germany somewhere. I may have to modify the set up for the operation of the valves and increase the diameter of the pushers just like on the DOHC camboxes. My copy is also slightly different to the original in that it will fit standard crankcases. With the original cambox the top bevel sits 1/16" further out so if you find an original you will have to modify you crankcases to use the cam box.
-JdK- Have a look at this entry and this entry for more info on these camboxes