Just wanted to see what each of these engines could do in a Cen Magnum chassis now that they are both about the same price and available at less than $130 new. After braking them in and running them around for a few hours what I found is they are very close in performance. The 3.3 is a high RPM engine with good power from mid range to top end. The OS strength was at the bottom end to mid range where I had to back off numerous times due to wheel stands but did continue to pull hard through all RPM ranges. After running these two engine I find that they are as strong as some low budget .21 big block engines but without the high torque axle breaking issues. Of all the engines I have run in the Cen 1/10 chassis, Ofna .15R Force, .18 XTM, .18 DTX, .18 Sirio, OS .18CVRX, and .21 Vertex, these engines have the best performance to date.