Originally posted by cdelong
stock nova based .12's are around 0.018" (0.03mm). Thats not the shim size- it's the head button to piston clearance. Each set varies a little with manufacturers.
I usually measure my clearance by taking the head off and placing a small ball size piece of clay on the head button. Re assemble the engine and rotate it only one time. Take the head off again and measure the thickness of the clay with some calipers.
I would think you are good with 0.015"- 0.018" running 30%.
thanks thats a great idea