powerful off-road motor to consider:
RB C5-buggy (personal fav), WS7-II,
(RB distributed by sigma trading http://www.sigmatrading.com )

Novarossi RX21P5
( TRINITY PRODUCTS)

TOP PT 21 CLB,
(RON PARIS RACING, http://wwww.parisracing.com )

REX PR 21 CLB,
(MUGEN SEIKI RACING, )

other engines to consider .. any of the JP black off-road engine or RR moded RB.

but... the more power the engine have the more maintenance it needs. (high power = more ware and tare). RB for example recomend con-rod change after every 2-3 gal. (racing condition).

more info on
http://www.rbproducts.com/rbww/ubb/c...ultimatebb.cgi