I don't think the Vincent engine is well equipped to handle big upgrades in cam, follower, valve, and valve spring up grades.........i don't exactly know how they've done it but the Horner brothers seem to get good results.......I have spoken to ken about this many times and he often says the areas to work with are too small and restrictive........Obviously their fix was to go with roller followers, ratio type rockers and a full pressure oil pump system........On their 2 valve twins the valves are 2.25" titanium and run 170 Lb seat pressures.......My experience with cams that wear prematurely seems to be from either the cam and or followers not being hard enough.......The oil delivery through the cam spindles is very important........relying on the oil returning down the pushrod tubes is a bit of a myth, this applies to the center 2 tubes but the outer 2, the oil simply runs off the bottom edge of the tube and misses the cam all together........One answer i have heard of is to blank the lower oil returns from the timing chest back to the crank case......You may get away with this on a street engine, but on a racer it will pump oil out of absolutely every where. The timing gears act like a giant oil pump and throw oil in mass........however, this oil does not actually get to the cam lobes where it is needed.......My answer on the single racer was like Marcus's where extra oil is fed into the cam spindle and thus pumps a lot more oil out of the holes in the cam lobes directing oil exactly where it is needed. So far it looks good with no signs of either the cam or followers breaking up........I am still running the Morris castor oil in this engine, so with the easy ability to remove the timing cover (cometic gasket) I will keep a close and regular eye on them..........Cheers.