valve chest breather/diagnosis of contributing issues

[JonE]

Bob - any indication of what those "quite large gaps" would be in numeric terms?

[Hedd_Jones]

with the top end problems on the RP here, I did for a split second think about re tempering the rings in it for shits and giggles.

My man, who makes his own rings (non IC applications) tells me if they are heated to beyond the critical temp they also grow, which means the gap is reduced. Which if excessive might be good. But it does mean they are not quite as round as they were before, and need a lot of descaling. So they will need a good bit of running in.

Given until I take it apart, I don't actually know what is wrong, that is where I left it.

My view is unless your leaving clouds of blue smoke, wait till the winter to mess with it.

[Bob Culver]

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.