I think that you will find that R – R invented Wellseal, and Hylomar in their Research Department, many years ago.
Wellseal was used to seal the wet liner to the recess at the top of the cylinder block on the C Range engines. Messy (and smelly) stuff as it seemed that only trichlorethylene would dissolve it, to clean hands or tools, or anything else. For many years trich has been banned, because of the effect of breathing in the vapour.
At Perkins, Hylomar was used extensively for many years. Both are non setting jointing compounds, unlike Hermetite, which will set like concrete, if not harder, and has to be virtually chipped off.
If the machined surface is reasonably flat, and has a good finish, applying a sealant, such as Wellseal, Hylomar, or silicone rubber results in a metal/metal joint, with the sealant merely acting as a gap filler where the surfaces depart from ABSOLUTELY flat. Again, you need something fairly exotic as a solvent ,such as methyl chloride, for Hylomar. Silicone rubber is good, but beware of excess being squeezed out to block small passageways, such as steam ports if used on cylinder covers.
There are grades of Loctite, and probably other anaerobic sealants, that will do the same job.
Howard