Vavle train oiling

Okay, so what exactly is the problem with my engine then?  I understand that oil pumps either work or do not work at all, they do not work poorly.  With that said, what else would cause the low oil pressure condition?  Too much main bearing clearance due to excessive wear?  I am assuming my poor valve train lubrication is due to the low oil pressure (insufficient oil pressure to pump oil up to the heads), correct?  
1969 GTO, YS code 400, 350hp/445 ft lbs of torque (stock specs), LT headers, H-pipe, 750 Holley 4160, Ignitor II ignition.  Complete Painless wiring.

You could have a weak oil pump but it could be a problem with the bearing clearances.
Yes the poor valve train oil is most likely due to the low oil pressure.  
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Something else that might contribute to the low oil pressure is the fuel in my oil.  The old carb was dumping way excessive amounts of fuel into the engine.  The spark plugs were all fouled out and fuel was ending up in my oil.  I fixed that with the new carb and then changed the oil, but inevitably, there may still be some fuel in the oil because not all the oil comes out through the drain plug or oil filter.  Maybe there is still some fuel in the oil, thinning it out, and contributing to the low oil pressure.

I always heard that oil pumps do not get weak and put out low pressure, but that they either work or do not work at all...  
1969 GTO, YS code 400, 350hp/445 ft lbs of torque (stock specs), LT headers, H-pipe, 750 Holley 4160, Ignitor II ignition.  Complete Painless wiring.

I have seen oil pressure issues not often but have seen were the oil pump was weak and not pumping like it should.
Fuel in the oil will thin it out a lot depending on how much gets in the oil but still the oil pressure should not be that low.
What weight of oil is in the engine?  
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Rotella T 15W 40.  Also, even though the engine is really clean internally as I saw when I did the heads, is it possible that the oil pump screen where it picks up oil is gunked up and clogged?  The car has done years and years of sitting.  
1969 GTO, YS code 400, 350hp/445 ft lbs of torque (stock specs), LT headers, H-pipe, 750 Holley 4160, Ignitor II ignition.  Complete Painless wiring.

Yes that is possible as well.  
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Is it possible to access the oil pump from underneath without removing the engine from the car?  
1969 GTO, YS code 400, 350hp/445 ft lbs of torque (stock specs), LT headers, H-pipe, 750 Holley 4160, Ignitor II ignition.  Complete Painless wiring.

Yes it should be as long as you have enough room to drop the pan. if not then removal of the engine will be necessary.  
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I could also loosed the engine mounts and jack up the engine if the pan doesn't clear.

My boss said that my oil pressure numbers were normal, and "not bad."  And other sources tell me that my oil pressure is good too.  Is it really bad that the engine has 20 psi at idle, and 50 psi at cold start??  
1969 GTO, YS code 400, 350hp/445 ft lbs of torque (stock specs), LT headers, H-pipe, 750 Holley 4160, Ignitor II ignition.  Complete Painless wiring.

Yes you could if needed.
Ok my 301 Pontiac in my green regal but has a new oil pump has 35PSI at hot idle @ 750RPM and 55PSI hot @ 1000RPM and 60PSI cold idle @ 1000RPM and it has 136,000 miles on it.  
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Do you have a "high pressure" or "high volume" oil pump in your Regal?

By the way, I know 301 engines are not performers, but how does it do as far as acceleration and power?  Is it a stock 301?  
1969 GTO, YS code 400, 350hp/445 ft lbs of torque (stock specs), LT headers, H-pipe, 750 Holley 4160, Ignitor II ignition.  Complete Painless wiring.

Hi pressure w/ screen which is all you can get through summit.
Yes it is stock but has had a new oil pump,cam&lifters and a timing set all stock replacement.
Oh and it performs very well for a 301.  
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In one of your post you say you only get 15PSI what RPM is that @ and is that hot or cold.  
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Actually now with the new carb on it, the needle vibrates between 16-17 psi at idle in park at about 750 rpms hot engine.

What kind of gas mileage do you get with the 301.  I can imagine that it would be too bad like my 400 gets.  I want to buy a 301 equipped car for a daily driver.  
1969 GTO, YS code 400, 350hp/445 ft lbs of torque (stock specs), LT headers, H-pipe, 750 Holley 4160, Ignitor II ignition.  Complete Painless wiring.

Not sure what the gas mileage is but it does not burn much even with the 4bbl carb.
There is nothing wrong with a 301 Pontiac Engine just don't expect a lot of power.
16-17Psi at hot idle  is not good.  
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