well for a .18 sized engin i would go with the OS 18 cv-rx or the hpi 18ss engine, or an OS 12cv-rx would work good too, those are all under $190 usd
i have an os 18 cv-rx, good engine, also ahve an 18ss, havent ran it in a while, but it runs strong, revs high, even more powerful if you modifiy it