Build your own engines, or have them built?

i dont have a machineshop but im not simply asembling my engines either i carefully check every part and clearance as i put it togheter,if it needs to be corrected i go to the machineshop,but this way i know its all up to me if it blows or if it works and that i have done all i can to make sure it survives as long as one can demand,headwork was left to someone that realy knows what he is doing,since i didnt have the time and tools for it,not enought reserch time either to learn how to port the heads