I assume that the sprocket plate is tight enough, but I don't really know for sure. The other ends are plugged with either a bolt or the drive for the tacho generator.
I have 2 pairs of original S1 cams at home; they are not threaded. I don't have any later cams.
Here's a picture of two S1 car heads I did a while back; no plugs in cams.
I also have a pair of new billet cams, they are threaded and provided with a plug.
Hope this helps.
Andrew.
881824, 1E21538. 889457. 1961 4.3l Mk2. 1975 XJS. 1979 MGB (supercharged).
Adelaide, Australia