I bought two stuart steam engine castings kits at NAMES a couple years
ago. Every so often I get them out and do a little work on them.

I was wondering how much piston/cylinder clearance is required.
The bore is 1 inch and the stroke is 1 inch. The cylinder and piston
are both cast iron and the piston is suppose to have 1 ring.

Should I stick with the CI ring or change to a teflon ring like
PM research uses?

I hope to build a PM Research kit and run them on live steam but
I suspect they will run on compressed air most of the time.

chuck