STAMFORD — After 19 years in business, Clearview Capital’s investment strategy has not changed much. Its record has argued for staying the course. The Stamford-based private equity firm is riding the momentum of two recent deals for companies that were each sold for several times the price for which Clearview bought them. Such results are nothing new for the group. Clearview officials credit their series of strong performances on a steady strategy that values the growth of small but promising businesses.