I have a HPI rs4 rtr evo3+ and i need a new engine, i want to get an O.S engine becuase i know there reliable and its easy to get perts for.

my question is what O.S engine is the best( fastest, most reliable)?[/FONT]

Going with OS then I would go with the TZ series, the TZ 12 screams. It also depends on weather you want pull start or box. I don't think they make this engine pull start but the TZ 18 does come pull start or non pull start. The os cvr 18 is not bad eather. Not quite as fast but has alot of torqe and only cost about $120 (much cheaper), and is great if your just bashing.