Oil pressure

[Wannabe]

I saw a lot of similar conditions in these threads but mine is still different so here's my story. I bought a 73 C10 stepside from a guy who had no clue to what was going on. The factory gauge didn't work which was no big deal because I planned on putting in aftermarket gauges anyway. I got the truck just about ready to go and when I fired it up the pressure gauge went to 20 and stayed there. As it got warmer the pressure would drop. At 160 idling in gear, pressure was zero. I shut it down and dropped the pan. I looked at the pump and there was no pickup on it. Even this was not the low pressure source because the pump is submerged. I dropped #7 rod cap and the bearing was perfect, I took the bottom off the pump and there were some super fine scratches but still no reason for the pressure to read 0. I added some small washers to the end of the spring in the pump. This had no effect either. So I was frustrated and I put in a full bottle of 90 wt. gear oil. STILL no increase in pressure. Pulled the valve covers and it was oiling but not as much as a normal sbc but still adequate. I checked the mechanical gauge with a known good gauge,, same thing. Anybody got an idea?

 

[Rusty Nail]

Vulcanized oil clogging the push rods is my idea. 90wt oil only exacerbated the issue

How old is the oil? Running an engine with expired motor oil even for a little bit is not okay. Go ahead and pull out the money for an oil change, big spender.

Does Motor Oil Expire? When To Change Your Oil

You've probably seen a lot of conflicting information about whether motor oil expires. Here's how to tell if your oil has gone bad, and what you can do about it

mechanicbase.com

Might could get away with running an oil system cleaner or 1/5 of transmission fluid but stay far far away from putting 90 weight gear oil into your crankcase. There's never a reason for that. YOU want thinner oil, not thicker, in this case.
Maybe add a quart of diesel fuel, not gear oil.

Hope this helps!

 

[Rusty Nail]

https://www.dictionary.com/browse/vulcanize

 

[Wannabe]

Vulcanized oil clogging the push rods is my idea. 90wt oil only exacerbated the issue

How old is the oil? Running an engine with expired motor oil even for a little bit is not okay. Go ahead and pull out the money for an oil change, big spender.

Does Motor Oil Expire? When To Change Your Oil

You've probably seen a lot of conflicting information about whether motor oil expires. Here's how to tell if your oil has gone bad, and what you can do about it

mechanicbase.com

Might could get away with running an oil system cleaner or 1/5 of transmission fluid but stay far far away from putting 90 weight gear oil into your crankcase. There's never a reason for that. YOU want thinner oil, not thicker, in this case.
Maybe add a quart of diesel fuel, not gear oil.

Hope this helps!

I find it hard to believe the pushrods are clogged, when I rev it a little bit the oil hits the fenderwell. The oil was changed just before I got the new gauges because I wanted it ready to go when the new oil, (Valvoline 10-30,, Wix filter). I'll get some diesel fuel and run it through the engine

 

[Rusty Nail]

The gauge shows 20 psi THEN it drops.

My second idea us a build up of electrical resistance in the gauge power.
Did you install the new gauges or only buy them?
I don't think its very easy to reach the oil pan through the cylinder head oil returns with a clothes hanger or something..but if the oil pump didn't gave a pickup on it?

Its only so many causes but I feel like you're leaving stuff out, like new oil for example, which makes it harder to think to good ideas and try to help.
Pretty shocking you pulled the oil pan so soon in that story..where did the pickup go?

 

[Wannabe]

Cold startup, pressure is 18-20. As the engine warms up the pressure drops,, at 160 degrees the pressure is 10-12. If I drop it in gear pressure drops to zero. Gauge is brand new mechanical, no kinks in tubing. Oil was new when I first fired it up and I noticed the issue. Valvoline 10w30 and Wix filter. The pickup was laying in the pan but at idle this is a moot point because the pump inlet is submerged in oil

 

[Rusty Nail]

Reckon you oughta have a gander at the distributor gear then. They got that piece of plastic that connects the oil pump drive shafts together, or whatever you call em. The chances of having a bad oil pump have got to be astronomical but anything is possible. They say..
If you watch the engine run without valve covers and there's no oil coming out of the pushrods..then what does that mean?
Makes ya wonder about the distributor and cam gear? You've got bigger bearing troubles than you thought? There is some clog in the oiling system?

Combustion cycle of the engine spins the cam which drives the distributor which spins the oil pump.There's nothing else to it... It's all connected. Can't have one without the other.

 

[PrairieDrifter]

If the pickup tube was off, the oil pressure is what it is. Even under light throttle it would suck the oil below pump level. You could try replacing the oil pump, that's your only option. Otherwise the damage has been done, you could find another pressure gauge and test it again.

But at cold startup is your highest oil pressure. Then normal operation is as the oil warms up you lose oil pressure, as the oil thins out. In gear is your lowest idle, so obviously completely lowest pressure. Run it till it can't or replace or rebuild.

If you're getting pressure it's not the drive coupler. It could possibly be a stuck oil filter bypass, or partially stuck but I highly doubt that.

 

[Rusty Nail]

Coupler! Thats the thing. But them parts arent gonna come apart even without a coupler. I agree . Without a pick up its

 

[Buck69]

You need a pick up tube and any scratches in the pump indicate it is likely trash. Internal clearances dictate whether it is not.
When checking bearings for damage, you should also check the farthest from the pump. Although the closest are the first to get air, the farthest are the last to get the oil.

 

[dvdswan]

Change the oil/filter, connect an oil pressure gauge to the side of the block by the oil filter and retest. Chances are it's a tired engine, oil galleys are partially clogged, oil pump is tired, old oil in the line from the top of the block to the gauge, etc.

 

[85K304SPD]

That motor is probably worn out. If you are trying to keep it running, throw in a new high pressure oil pump and pick up in there and you will probably get some oil pressure. No telling how long it will last. It would be a good time to pull it out and rebuild it.

 

[Wannabe]

Reckon you oughta have a gander at the distributor gear then. They got that piece of plastic that connects the oil pump drive shafts together, or whatever you call em. The chances of having a bad oil pump have got to be astronomical but anything is possible. They say..
If you watch the engine run without valve covers and there's no oil coming out of the pushrods..then what does that mean?
Makes ya wonder about the distributor and cam gear? You've got bigger bearing troubles than you thought? There is some clog in the oiling system?

Combustion cycle of the engine spins the cam which drives the distributor which spins the oil pump.There's nothing else to it... It's all connected. Can't have one without the other.

 

[Wannabe]

The engine runs too smooth to be the distributor gear and I know the coupler is good because the oil pump gear would not drop down more than the coupler allowed. With valve covers off the pushrods are all open and oil is coming out, if I rev it, just a little the oil shoots all the way to the fenderwells. I have to think blockage in the engine to gauge line but when I was getting things buttoned up I had put the line on the block but did not get it tight, something interrupted me and then I forgot all about tightening it. When I fired it it blew the line out and it pumped out 3 quarts of oil in seconds so I don't see a blockage there. Since I have already looked at a rod bearing I know the engine still had sufficient oil so no harm was done except to my garage floor. I think I might try a pump but one thing I am wondering about is the oil galley plugs at the front of the block.

 

[Wannabe]

Change the oil/filter, connect an oil pressure gauge to the side of the block by the oil filter and retest. Chances are it's a tired engine, oil galleys are partially clogged, oil pump is tired, old oil in the line from the top of the block to the gauge, etc.

I was just thinking about your suggestion, that will be my next step, at least it's free, I refuse to just throw parts at it. Thanks for the suggestion.