Upsure Farm Engine question

[HobbyNut]

I built an Upsure Engine that was detailed in Strictly IC a few(!) years ago, but I think there may have been a mistake in the plans, as My piston only came to about .168" of the top of the cylinder. This meant that I had almost no compression. I could put my hand over the bore and the piston would not fall out, so sealing was not a problem. Anyone out there that can tell me from first hand experience, how close is the piston to the top of the bore? in your build.

[Robert Hornby]

A friend of mine built a model hit and miss engine which ran sort of OK but was not really happy with it. He broached his concerns to our club meeting and was advised to check the compression ratio. He did this and found it to be 9:1, way too high. The advice was it should be around 4.5:1 for smooth running. He made a new piston and the engine runs like a gem.
Robert