Oil pump

[CipherLogic]

Just got engine and tranny back in truck, tranny was rebuilt, engine was just degunked and resealed.

1st start had about 70psi oil. Then today tore down the starter and cleaned all the contacts in the solenoid and ran all the belts and put the front clip back together added water etc. Oil was at around 50psi on first pop, slowly dropped to nothing.

Strange clanking on the bottom end, hard to tell since it's open headers and I can barely hear myself think much less distinguish a sound.

What are the odds that the pickup decided to screw up my night and fall off into the oil pan and is causing the clanking and oil pressure to be nil?

Also, how much effort is it to pull the pan with engine still in?

EDIT: 1985 c10 / 305

[bake74]

     I would say it's a safe bet that either the pick up tube fell off or something clogged it up.  I know you said it was resealed, but I have seen it before.
     As far as how hard without pulling the engine.  You more than likely will have to raise it at least some to get it off completely.

[CipherLogic]

I hate hindsight, should have spent a few bucks on a new pump while I had it out. Will be pulling the pan in the morning.

[CipherLogic]

Got the pan off without having to move anything.

Oil pump and pickup still attached.

Fresh oil was thoroughly grungy, no metal in pan but plenty of the old burnt oil/particulate. Oil was blackish with a hint of grey. Felt like fresh oil but looked old. I had planned on changing the oil a couple times to get all the sludge out.

The oil pressure gauge is a mechanical gauge plumbed into the port on the back of the engine near the distributor. How likely is it that this port got stopped up and does anyone know of a way to inspect the oil pump by hand to make sure it is the cause? 

Also, could the oil filter got slap clogged up from this and could that cause the low/no oil pressure?

[roundhouse]

What did you use to de- gunk the engine?

Probably some sludge in the filter

Usually with old engines its best to just leave the gunk  than stir it up

You need mufflers on it so you can tell f it's
Making any death rattles

[bd]

That's a frustrating bit of luck. 

Remove the pump cover and inspect for gouges and galling.  Then remove the pressure release valve and give the pump a thorough cleaning -OR- just replace it - they aren't that expensive.  Since it clattered, take the time to at least inspect the rod and main bearings.  Peer upward and take a close look at the cam lobes.  Carefully cut the oil filter open for inspection.  "Oil was blackish with a hint of grey," suggests very fine metal particles mixed with sludge.  Check the oil very closely for a "silvery glint" under good directed light.  Drag a strong magnet through the oil and pan just to make sure there's no steel moss.

Remove the oil gauge line at both ends and spray it out with some carb cleaner and compressed air.  Check the oil pressure with a mechanical test gauge and compare it to the dash gauge.

Frequent changes with fresh 30wt oil and filter are a given until the oil drains clean.

[CipherLogic]

De-sludging it with fresh oil. When I had the tranny in the shop I got after most of the sludge with putty knifes and a spudge and a hoover.

The engine originally leaked from every seal so the oil was never changed it was just constantly added to.

[SomeTexan]

Sounds like a main bearing spun. You will often notice a drop in oil pressure when they turn, before the clanking starts.

[CipherLogic]

Sounds like a main bearing spun. You will often notice a drop in oil pressure when they turn, before the clanking starts.

Worn out, not spun though.

Will there be a tactile difference in how a worn out oil pump feels spun by hand compared to a new one?

[bd]

How does the crank look?

If you started this ordeal with 70 PSI, the pump isn't worn out, but there's a good chance that the pressure relief valve is sticky.  You probably won't be able to 'feel' any difference between a new and worn out pump, unless the gears are galled.  A thorough inspection following disassembly and cleaning should tell you what you want to know. 
Personally, I would install a new Melling standard volume/pressure pump and hardened drive shaft.

[CipherLogic]

How does the crank look?

If you started this ordeal with 70 PSI, the pump isn't worn out, but there's a good chance that the pressure relief valve is sticky.  You probably won't be able to 'feel' any difference between a new and worn out pump, unless the gears are galled.  A thorough inspection following disassembly and cleaning should tell you what you want to know. 
Personally, I would install a new Melling standard volume/pressure pump and hardened drive shaft.

I already got a new melling pump/pickup and hardened shaft.

Going to have to get a new rear seal and rear main bearing since I can't in good conscience put that bearing back in.

I believe the crank looked good, I didn't give it a real hard look since just before than some nasty oil dripped into my eye and it was burning like fire.

I should have it all back together mid morning tomorrow, will also put an air tank up to about 60psi and put it to the back of the gauge to be sure it didn't fail.

Everything on this truck is 9 to 29 yrs old so I wouldn't be surprised if the oil pressure gauge keeled over.

This engine was a rebuilt 305 me and my dad put in when I was in HS like 16 years ago.

[CipherLogic]

Need help identifying the old bearing as the numbers are of a bearing I guess ACL no longer sells.

I imagine it's .010 but want to be 100% certain before I go back with new one.