I think I found why oil pressure is low...

[wallaka]

Well, I finally got around to pulling the main caps and this is what I find--
I started with No. 7 because it is closest to the oil sender.

Notice the copper colored line?
And here's the thrust bearing--not sure if the sides are supposed to look like that. I suspect not.

It's possible that there was some grit or something on my glove when I assembled the engine, or some bearing material left in an oil passage from when I spun those bearings that the steam-cleaner couldn't reach. That might account for the #7. Not sure about the thrust bearing, though. The rest looked good, and I can't see or feel anything on the crank. I had the crank resurfaced when I rebuilt it.

 

[addo]

I don't believe that's enough to lose significant oil pressure.

Checking the oil pump for clearances would be a good start, then inspecting the shaft for 100% engagement, then looking for suction leaks in the pick-up.

 

[wallaka]

Just seems strange that all of a sudden it would lose pressure. It was fine at first. I'll keep looking--what should the clearances be in the oil pump?

 

[addo]

You've got a gear mesh clearance, and a coverplate clearance.

Clearance to the coverplate should be air-gap only. Mill, lap or linish the coverplate if need be to get this right. With match-marks aligned on your inner and outer rotors, the clearance between outer rotor and case should be 6-12 thou.

Drive shaft needs to be a sliding fit - 1½ thou is recommended.

I also have a figure of 9½ pounds at 1.078" compressed length, for the bypass spring. You could check this with some home scales, a crude lever (like a weak valve spring tester) and a cardboard length gauge.

 

[nitrousnick]

fyi,I long time ago I picked up an adjustable rocker assembly from a guy that blew up his 200.When I got it home my dad noticed the shaft was upside down,oil holes on the top,this may have lead to low oil pressure and resulted in his engine blowing up.

 

[wallaka]

Hmmm. That would be easy to do, wouldn't it?

 

[Lazy JW]

I don't believe that's enough to lose significant oil pressure...

Yup. I have torn down a fair number of engines that had the bearings worn completely into the copper and still had decent oil pressure.
Joe

 

[XFlow_Fairlane]

def an oil supply issue there. looks like you had some debris in a galley hole or somewhere when you assembled it.

btw I like using oven cleaner cleaning inside the block. will remove all oil film and once rinsed gives you a real clean surface.

 

[MustangSix]

I had one pop the plug from the camshaft oil gallery once. Caused an internal oil leak that dropped pressure to near nothing. Look for the plug behind the cam gear.