I built a 3.1 for my Trooper based on Goeffs, one tough engine, but it started loosing oil pressure after a few years, so I figure I did something wrong. But it was running great until then. I am now in the process of putting a 3.4 in my Trooper, might get it fired up today. Took it from a 95 Camero. I have had several of the 4 cylinders also but like the v6 better.