will your oil pressure drop after you install a blower,my used to run 75 cold and 60-65 hot,idle at 50 hot.now its 65 cold and 55-58 hot and idles at 45 hot,the moter is a 509 merlin with a 871 bds blower.thanks i also changed to a solid cam if it makes a difference

I can't imagine why oil pressure would drop with the addition of the blower. 45 pounds at a hot idle isn't bad, I'd guess you're fine.

I'm running at about 75-80 pounds at a cold idle (~1500RPM) and about 60 pounds at a hot idle, that's with a high volume pump in a tall-deck 427 & 6-71 that's all fresh and new.

One thing that might account for the differences are idle speed, are you measuring oil pressures at exactly the same engine speeds? Just a slight change in engine speed can radically change cold oil pressure.