Dang! I fat-fingered the keyboard and lost several paragraphs of a reply! There is a detailed procedure on how to measure cylinder taper accurately with nothing but an old piston ring and a feeler gauge in John's tech tip on rebuilding his 261. Stand by- - - - -!
Jerry

Try this method: https://www.stovebolt.com/techtips/engines/cylinder%20taper/index.html

Note: A ring running in a taper-worn cylinder at 2000 RPM is flexing 60 times per second, trying to maintain contact with the cylinder wall- - - -expanding and contracting in less than 2 inches of piston movement. It doesn't take long for the ring to lose its spring tension and stop sealing compression and/or oil.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!