I use a grinding wheel from a steel cutting chop saw. its about 13 inches across and is very flat. I bought it for $3.99 at Big Lots. I just laid it flat on a wooden table rubbed the head on it turning it as I went. It raised my compression from 120 lbs to 160 lbs in about 15 minutes and I noticed a big improvment. It might be fun to raise the compression to about 240 lbs and experiment running methanol at a very rich 7:1 fuel air mix and 15 percent oil.