Your way of thinking is wrong. A car engine has a load path outside the water jacket. The Norton barrell can't provide such a load path, especielly if the sleev breaks through the base casting. A sleeve should not be considered a stressed member unless it has a 100% thermal fit surface contact.
The cylinder barrell comes under tension at the combustion phase. The friction achieved between barrell and sleeve when sleeve breaks through is obviously small.
-Knut
