Question: I am attempting to install the cams, and shim the tappets, but my cam lobe is contacting the tappet guide. My first thought was maybe one “floated,” but further analysis reveals that it is all of them. I have been following Des Hammond’s book, Power tuning XK engines and have scoured the discussion boards and I cannot find any instance where the tops of the tappet guides need to be machined to allow for the cam lobes to clear. I am using a performance cam from Piper Cams, which does have more lift than stock, but so far I haven’t been able to find a documented solution. Piper Cams have been less than helpful.
I am rebuilding an XK engine for my Series II XJ6. Engine block and head are S III components. Machining on the head included a few new valve guides and resurfacing the deck. New performance valves, and stiffer springs have been installed. Due to the laborious nature of shimming the tappets I intended to tackle that portion myself when I encountered this problem.