w8ye, yeah you might be right, it most likely is 1/4"-28 (coarser) insted of the finer 1/4"-32. William, I think that's what I'll try doing to get the exact thread type. As for the cylinder being like an OK .60 you might be right. Is it possible that IT IS the cylinder from an OK .60? The .55 displacement that I stated is a somewhat rough figure. I was able to measure the bore accurately with my Starrett (just to brag a little hahaha)...but as for the stroke I just got a pretty good but rough idea. And I came up with .54 as the displacement. This of course is closer to .60 I'm sure since I didn't take into account the fact that the piston top is somewhat sloped. It's sloped/cut out on one side to make the exit of exhaust gasses easier and it is sloped on the opposite side as well to ease the passage of the fresh charge into the combustion chamber. PLUS, there is a good amount of space left at the top of the chamber when the piston is at TDC (although I didn't actually cc it to get an exact figure). In any case it looks like the compression ratio is not all that high and so that's why I perhaps though that it might have been an ignition engine originally. I have my doubts as to whether it will even run with a glow plug.

Anyways, any thoughts about the rpm range on these old engines and whether a 'modern' .35 or .40 r/c carb would be good for this engine?