Hi Mike, Now I am not sure if you are pulling my leg, or if the Wilkinson chain of hardware stores have not reached your area. I suppose I could have said B&Q
Type of silicone?
Well to be honest I have always just used domestic transparent RTV (Room Temerature Vulcanising) general purpose silicone in a cartridge.
More or less what you use to seal the bath! But be wary, because there are many less expensive sealants that are not based on silicone and will not stand the heat. I also use this to seal the exhaust, ie no gasket, just metal on metal with the silicone. Must have saved a fortune on gaskets over the years! To be fair, it was necessary to find another way.
If you look at the skirt thickness of a 600 barrel at top +60 overbore. That is 3″ with Silk pistons, it is very thin and frail. As I make Aluminium blocks, I increased sizes to give a decent skirt wall. In this case, the conventional cork rings do not fit. I just run a good bead of silicone round the sholder where the cork ring usually sits. I never had a problem. It would be interesting to fit a Detachable head as I do with thin shim rings instead of the thick copper asbestos gaskets. As long as the pistons do not hit the top, it could give a nice compression boost. The last time I was in town, I called into a plumbers merchant and bought a cartridge of Dow Corning silicone “Flue Sealer”. This is a silicone made with special attention to sealing flues near stoves such as AGA etc. I thought I would try it out. It was not expensive and might have a marginally better performance on exhaust flanges..
I should perhaps add that I always degrease well before using silicone sealant or Loctite. Paul Dodds brought some expensive silicone sealant sold as a gasket substitute to a race meeting. It was many times more expensive than the cartridges I buy and did nothing different, except it set harder and was a swine to clean off when you dismantled things, then wanted to clean for re assembly. It works for me folks!