Hi Bruce,

Looking at the picture the larger one appears to have an angled plug, and the smaller one has a bolt on venturi. That rules out the .35 Stunt, and little brother .19 Stunt. The small one may still be a .19, Duke Fox made numerous versions of .15,.19,.25,.29. etc.

My guess is that the bigger one is a .36 X, or maybe a .29. These are less desireable than the famous .35 Stunt, but are still good solid engines. I don't need any more at this time, but can tell you that at swap meets and on various forums either of these usually bring in the $20 -30 range, maybe a bit more if they are in really good shape.