It's recycled aluminum. It cuts like butter w/ a dremel shaping bit. don,t even try the grinding stones... They clog/shatter in no time
I used my drill press just like a mill, and took out about an 1/8" at a pass on my engine cases.
All you REALLY have to work on is matching the intake, and head port. Once you get a good funnel shape you have increased velocity, and HP.
Look at the HPI Ign. It's a bad ass set up. Just the inner rotor set increases rpm/hp by shaving off 2-3 lbs from the crank, It's instant revs.