the bypass is behind the big nut on the pump housing....Note, I don't remember if the small block has a nut behind the valve, or if it is retained another way...I have not seen a small block in a long time...have to go look for a pic. According to the manual, there seems to be a cotter pin thru the housing that keeps a retainer from popping out, then comes the spring and valve....yep, that is what the pics on Summit look like as well...remove the pin, while putting something over the back of the hole that the pin is keeping the retainer from popping out of...this to catch the spring as it unloads...remove the valve...check for debris, a burr, or anything that might keep it from sealing completely on the bottom end...
strange? well, it means something is wrong. There is not enuf oil being circulated when the engine speeds up to maintain pressure so the pressure drops as the volume increases....should not happen so something is wrong. If the high pressure bypass is not closing all the way, then it will bleed the volume back and the pressure will drop. If the pick up tube is cracked, it will suck air; if a galley plug was left out, or fell out, the oil will leak out that hole and pressure will fall, and so on.
At the simplest, pressure is a measure of the resistance to flow so any "leak" will increase flow and drop pressure
