i've got an '86 gxl that will read 30 psi oil pressure at idle, however when i rev the engine to 3000 and hold, the pressure will slowly drop and start to weaver between 10 and 30 psi. i've consulted the factory manual and it suggests that it could be:
oil leak (i checked, nope)
insufficient oil (checked again, nope)
worn or damaged pump gear
clogged oil strainer
malfunction of oil pressure control valve
malfunction of oil cooler bypass valve
malfunction of oil pressure regulator valve (different from control valve?)
clogged oil filter (changed that a month ago)
malfunction of eccentric shaft bypass valve
excessive clearance between eccentric shaft and main bearing

i really don't want to have to tear the front of the engine down to rebuild the oiling system, any help in pinpointing the problem would be appreciated!

 

The stock gauges are far from accurate. Go by an aftermarket mechanical Oil pressure gauge, hook it up and see if there is a difference. Read the FAQ sticky as well.

 

yeah get aftermarket gauge first before you start worrying

 

Check your oil pressure sending unit as they do break down. Had the same problem and replace mine with a new one. Problen gone.

 

Sounds like the front cover oil o ring. Mazdatrix has a great page to show this.

 

Yep, front cover O ring or poor quality oil, or bad oil pump

Did you do some front cover engine work recently or was the motor rebuilt recently?