I'm thankful for the advice, but a friend in Shetland told me a story. He had a Chater-Lea, which has an overhead face-cam. The numpty (a person of low competence, see under "Westminster, recently elected") to whom he gave the cam spindle to fix, thought the 0.005" increase in diameter where the cam fits was a mistake, so he ground it off. "If you don't know, just bash on", as Andrew Lansley would say.
Even outside Shetland, Chater-Lea cams 0.005" undersize are rarely in stock in B & Q, so he had recourse to Captain Loctite, heavy-duty bearing fit company. Two years later, his Chater-Lea was still running perfectly. You may object that the ambient temperature in Shetland is low. I wouldn't argue. But it isn't low inside a Chater-Lea cylinder head.
Besides, Gary R sells good stuff.