I actually know very little about rotary engines. I have some aviation engine books but information on why & how they did things is actually quite sparse. They are not well documented & vary between models & manufacturers. I have LK Blackmore's (building the the quarter scale working replica) Bentley BR2. It has some FS pics & sketches interspersed but more for visual reference, again quite brief. Apparently the drawings have some boo-boos & omissions, I've never felt brave enough to build it. It has knackered better model engineers than me.
There is some documentation out there above the typical forum chit chat, but I suspect the real dope is locked away in museums & the craniums of those who maintain them.
Pre-Order and Advance Information for Rotary Engines Book
wobentleyrotary.com
There is a Clerget in Calgary which I have from authority was discovered brand new in a barn amongst the chicken dung. Apparently some found their way to farms as war surplus. Thankfully it never saw that service. That engine was one of the critical bits that made the Sopwith Triplane project proceed back in the 70's. I have some familiarity with that airframe, did some volunteer construction work in my teens. Its a work of art faithfully reproduced to factory drawings. But it will never fly. Maybe better that way.
thehangarmuseum.ca