I am converting an OPS maxi 30cc. This is an older glow engine with bearings all around and comes with a "walbro" type carb, it also takes a standard walbro as a bolt on.

The head is a turned disk that is held down by the head cover piece that you see. The current "head disk" is made for a glow plug and too thin for a CM-6 plug. It has about 0.040" squish band clearance as designed. The inside countour of the head is basically rectangular with rounded corners. Since I am making a new head disk should I make any changes? Tighter squish band? Increase or decrease the volume of the chamber? If I did want to change the volume of the chamber how do I detemine final compression ratio and what should that be? 10:1 for regular gas? So that is 3CC for this 30CC engine? Put it on a scale and see how much water it hold in grams? Grams = CC.