Newbie thinking bout building alpha engine

[Lugnut]

Need help in piston cylinder clearances. Brass cylinder and carbon graphite piston..hold thumb over cylinder and piston does not drop, release thumb and piston drops. Does this type of engine have air blow by piston or does it have to be air tight.

[Ian S C]

lugnut, that sounds about right. The cylinder needs to be highly polished in the bore, or the piston will wear quickly.
Ian S C

[Lugnut]

Thanks Ian , I'm in the deep thought process or trial an error process, but will be ready to build model soon. Thanks for your input.