on ratioed rockers etc. John, if you want higher lift it would be much easier just to use the mk 4 cams you started with. One of the things learned from the Mercedes F1cam developmeht program was that there is a point of diminishing returns for valve lift and also a point of no return whatsoever.. The mk 5s are a little lower lift than the mk4s because the program determined that there was no advantage in lifting the big Vincent valves beyond .440 (memory on the number, cant find the graph right now)
To put this in perspective, Irvings mk 1sgive .312 lift at valve, his mk 2s give .343 , Terry's mk 2s something like .370, mk5s .440 and mk 4s even higher.
So ratioed rockers with Vincent mk 2 s might be approximating mk 5 total lift? As Greg mentions, higher lift = higher valve train wear, so not much reason to go there if there is no power advantage. The mk5s took Malcom Hewitt to 162 mph at Bonneville.
To put this in perspective, Irvings mk 1sgive .312 lift at valve, his mk 2s give .343 , Terry's mk 2s something like .370, mk5s .440 and mk 4s even higher.
So ratioed rockers with Vincent mk 2 s might be approximating mk 5 total lift? As Greg mentions, higher lift = higher valve train wear, so not much reason to go there if there is no power advantage. The mk5s took Malcom Hewitt to 162 mph at Bonneville.