If you are talking pipe threaded square drain plug shown...Normally metal to metal will seal if torqued ...?maybe30-35 ft lbs? I don't think they ever spec that value. Looking at the pan bolts reminds me of my Intek ( I am not familiar with your engine). My engine is a vibrating beast which loosened all the pan retention bolts and several were sitting on their heads waiting for me to find them (hmm , do the designers know the engine vibrates apart?). Any way with crankcase pressure sections of the pan gasket got blown out. That leaves a step in the sealing plane and no tightening of the pan bolts really stops the leaking until you go in and replace. Mine is a weeper because of that. You got a clean engine there!