I have just fired up my rebuilt Chev 307, yes i primed it with a power drill but when i connect the pressure guage " i tried three" i am getting zero or no reading even when rpm is increased. i have removed the rocker covers and there is oil up top doing what it is suposed to but " No Registed pressure" rebuild inc block mach, bearings rings pistons gaskets oil pump etc etc. can any body offer any thoughts ?