it depends on what engine you want. i assume you are looking at a two stroke. i would not reccomend mds engines i have heard nothing but trash about them. same with magnums. however, thunder tiger (tt) makes some nice ball bearing engines, and so does os. i would personally reccomend os though because their break in really consists of 2 tanks. after 2 tanks, they will be almost at their beak. within the next 5 tanks or so, you will notice very little change.