block to crankcase joint - external seal?

[Nick Turley]

I am a convert to silicone gaskets for normal engines and have built several engines using them and they do not leak. This following the advice that Ruairidh kindly gave fitting them.
The trick for me is cleanliness - no oil - dry fit - nip down - nip down again next day - cut the excess off. Leave it alone and just use the engine.
The first one with a silicone gasket I did has now done over 9000 miles and is still oil tight, happy with that.

For high performance engines I like the Sikaflex idea ,making sure it is a high modulas with no gasket, applied correctly it glues the block on - does not leak and helps keep the block and case together.
One thing to note is that it does not achieve its full strength for about 5 days.
The only problem is getting the block off becomes a task and requires cheese wire to cut through the Urethane.

[Steve kay]

I thought that I had tried to contribute earlier today, taking a break from this very job. Some of my thoughts have subsequently been mentioned by others, but briefly; the only reason I have split the block from the crankcase is because the workshop is rather occupied by what may one day become a Chummy, currently making the chain block inacessible. I completely agree with all comments about engine removal being preferable, lying under the machine offering up big ends whilst the rain wets the feet sticking out from the side of the car might have been fun decades ago, but is not now. I was recruited to the silicon tribe by what I found removing the sump gasket, bought from Jamie, and the valve chest gasket made on the bench. Both were as clean and free of leaks or the slightest dribble, as if they had been put on the previous day. 

Work was interrupted by a visitor, with some old Seven newsletters and magazines. These told of The Seven Workshop at Denvers Yard, Barwick, or The 750 Spares Garage offering 18mm spark plugs for 57p a plug, or a head gasket for £2.80. And a photo of a sporting Austin, not one of ours but Louis Kings in the Twenty known as "Black Maria". Lots of Sevens to be seen at the Lawns this weekend, but sadly not a Twenty on the entry list.