How quickly should oil pressure come up?

1973dust said
It seems like the oil pressure on my 318 "comes to life" later than it used too and I'm trying to decide if I should be concerned or am just worrying too much as usual. On a cold start or a warm start after sitting for an hour, it will take 2 - 3 seconds for the mechanical gage to come up with the lifters also rattling. The lifters quiet down and the gage comes up simultaneously as expected. It's a 74 318 with 46000 miles that I'm fairly sure has never had anyone in the bottom end. Pressure on a cold start at 1300 fast idle is 66 psi. Once warmed up to 180-190, the pressure at 750 is 22 with 58 going down the road at 2000 rpm. It tops out at 64psi at 3000rpm warm. I am using 10w-40 Lucas "Hot Rod Oil" and a Wix filter. A blip of the throttle at idle instantly increases the pressure. What do you guys think?

I would drop the oil pan and plastigage the main and rod brgs. To do the mains you need to hold the crank up so the crank weight does not give a false reading. My method to hold the crank up is to remove the #2 aand #4 main caps and put a short piece of shirt cardboard or cereal box in and just snug the bolts. Then you can check #'s 1, 3, and 5. After that "shim" 1, 3 and 5 to check 2 and 4.
Also remove and check the oil pump clearances. To mark the pump gears to get gear teeth back with their matching teeth, mark with brazing rod sharpened. Works like a pencil but won't easily wash off. Gerotor pumps are hunting so do not matter. End clearance must be checked between the gears and pump housing using a straight edge and feeler gauges.
Cam journal bearings can also be a source of low oil pressure, but the mains and rods would be my first suspects and easier to change. 0.001" undersize bearings can be purchased if Std bearings are on the upper limit of tollerance.