Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

I am not a machinist but I am a good mechanic. 

First tip is do not cut a flywheel casting outer face and sides all the way down to the blueprint spec. 
Leave as much metal as you can. Take off just enough to show a nice bright metal finish. You can always cut off more later if you don't like it. You cannot easily add back what you shaved off. More rotating mass = longer freewheeling time.

The Debolt Star is a great runner. Call and ask for Paul or George.
www.deboltmachine.com 

The 1/3 scale Galloway is a great runner.   Ask for Doug.
https://www.ministeam.com/acatalog/MiniCasting-Hit-and-Miss-Engines.html
http://minicastings.com/acatalog/Hit-Miss-Engine-Kits.html

The Callahan is a great runner if you can find a set of castings, as is the Debolt Vaughn.

Bob Herder has castings for the vertical Domestic, hopper cooled and air cooled Domestic and the Stove Pipe Domestic.
His website is old but the phone number is good.
https://bobherder.tripod.com/