27-07-2021, 10:05 PM
Minx 1600 new .024 to .032. The wear limit (presumably for reassembly) for Beetle .035. The major Australian ring manufactuer ACL manual states max new .005 per inch dia plus .001 plus another .010 if rehoned.
Cast iron does expand when heated red but is weakend. (A trick applied to ci pistons.) Model engineers make rings by heating but probably not to scaling temp.
many ring sets were sold pregapped and for anything but min tolerance new bores gave generous gaps. many mechanics ordered next size up and gapped.
In days when Seven owners were impecunious old rings were reused, often a size down. no light should be visible!! normally second rings lead a very genlte life and can be reused. top rings wear vertically.
The oil burning of engines is often a puzzle. A slight chamfer on ring top edges may assist.