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

Hi Gil,..having no experience with re-working pistons, either method is probably same with such tight piston to liner clearance....I'm going the cylinder head "Spacer" plate route  initially, to see what the reduced CR effect does, is reversible & can be non-metallic thermal insulating to get more heat to the plug & Mixer for better fuel vaporization & combustion efficiency..just have to fab the pushrod extension..The cylinder liner deal is all about achieving a nano-size (> 0.001" dia) Telflon Coated steel ball Shot Peened Teflon impacted-deposited Oil Retaining micro-dimpled surface finish (instead of abrading linear crosshatch scratch pattern) to reduce O-ring oil wiping/starvation effect without abrading the soft pliable O-ring or causing compression leakage...Just Amazing what off the wall, exotic concepts the M90 lends itself to !! .....Cheers to you & family ...Happy holidays,...tom.