from what I read on the HPI Monster Truck forum you will need new bearings seeing the ones they supply with the K series suck

I bought a brand new K4.6 and put it in my savage and honestly its the worst engine I've had to date in anything(counting a .15FE with no compression in this). It broke a conrod's Brass bearing somewhere in the 1st 9-10 tanks (counting 6 breakin tanks) which then get wedged in the engine and was slowly ground up. I'm only glad the brass was so brittle they used that it didn't actually damage the piston or sleeve at all. I actually haven't even touched my savage since replacing the rod the engine irks me so. Think I'll save up some and get a LRP 30 or so next spring and maybe auction the K4.6 off.