RE: Diff. between .21 and .28
axisrc, I wouldn't suggest a Surefire .32. It's just not a very good motor. Believe it or not, but a lot of the top racers around Chicago who have the RBs and Novarossi engines have a healthy respect for the Sportwerks .26v2. If you're looking for a powerhouse motor that won't kill your wallet that's the motor. Another is the SH ProSpec .28. I run that and it's amazing for the money.