I still use the Castrol Valvemaster in my bikes (because I have some) but I believe it is no longer produced. This counters the valve seat recession caused on some old engines by lack of lead in the fuel. Ariel tended to use high quality materials and so there is no real need to use products like this on an Ariel since the valve seat recession is negligible compared with (for example) my Triumph 2000 car when I ran it on LPG in the early 1980s.
Square Fours are good at sticking valves. My MKII suffered from sticking inlet valves at start up after little more than 1000 miles from rebuild. This happened one morning after the Club Long Distance Run and Allan Simpson said to me "It's no good Paul, you will have to take the head off." This spurred the necessary obstinacy and I gave the bike a (very) good dose of Redex over a prolonged period. I never did remove the head - there was no need.
36 4G, 37 VH, 53 ex ISDT KHA (project), 54 KH(A), 54 4G Mk IV (project), Healey 1000/4 (project)
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser.