Can anyone explain the purpose of the pistons skirts hanging out of the sleeve at BDC? I'm a registered drag racer, and I have been building race engines for more that 30 years. In a real race engine, pistons hanging out the bottom of the sleeve is not a good thing and causes piston-rock. Several pistons have broken in a few of my little nitro engines and I'm wondering if piston-rock (due to several mm of the piston hanging out of the sleeve at BDC) is a factor. What do you guys think? I'm thinking of machining the piston so that there is no part of the piston that extends beyond the sleeve. Has anyone ever did this?