I have a Nova/Losi R21 3port and it is super smooth and gets 12mins. on a tank! The internals are great it has the R7 conrod and the Team CNC piston and the good front bearing (17011 I think) and I am surprised more people don't run this engine all the people that have let run or run with have nothing but good things to say about R21. I use a RE10 pipe for more power and RE11 for more runtime also cost less than $250! Give it a try you want be dissapointed!