Oil pressure help

[84prspctr]

i just got done with a water pump swap on my engine and the motor did not have a thermostat in it, so I put a 180 in. Before doing the water pump and thermostat I would run at 140- 180 degrees on the temp highway driving, now I run 200-210 highway driving at only 85 degree ambient. When I got the truck the oil was old and felt thin like 10w30 and it had 0lbs of pressure at hot idle and like 20 hot at 2000 rpm. I changed the oil right after I got it with 20w50 because of the very hot climate I live in and put in rislone zinc additive. It instantly ran 45psi cold idle, 15-20 hot idle, 25 psi at 2K rpm. Now with the thermostat running at 200 degrees it is at 25 psi at 2500 rpm, 0 psi 600 rpm anything above 1200 it jumps up to 20 psi and increases to 25 psi as they increase above that. It is going to start getting hot and stop getting cold pretty soon, should I just take the thermostat out and run it like it was before with no issues? Engine runs good no noises when idling with “0” psi. It warms up quicker with the thermostat but I can’t tell a difference after driving for 10 min with or without. I drove it over an hour straight without the thermostat and never had any oil pressure problems. It’s a 350 engine What should I do?
Thanks

 

[Ricko1966]

Check your readings with another gauge if you really have 0 psi at idle you have problems and we need to fix them now. 10 psi per 1000 engine rpm is acceptable 0 is not.

 

[Rickf]

"T" in a second gauge that is mechanical.

 

[75gmck25]

How do you know the specific temp readings on the highway, since the stock gauge in a ‘73 did not have any numbers on it? Is this the original gauge cluster, and/or have you added something aftermarket?
It’s also very common to have the wrong temperature sending unit (GM changed them several times over the years) in an older engine, and that would screw up rhe temp reading.

The original oil pressure gauge in the cluster should also be mechanical. Is that what you are using?

 

[84prspctr]

It has all mechanical gauges. Mechanical temp and oil pressure. It might have 5 psi at idle I’m not sure as the first tick on the gauge is 5 psi it is a short sweep gauge

 

[84prspctr]

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This is after running for a few min

 

[fast 99]

Need to verify temp. Depending on where the sender is located reading will change. Get a cheap heat gun. Harbor freight

Also need to verify oil p with another gauge. If actually 0 quit driving it. Have seen SB with 10 at idle run a long time. If no other noises that will work, not ideal.

 

[Rickf]

Look under a valve cover for sludge. If there is a lot of sludge be prepared to drop the pan and replace the pump or engine.

 

[75gmck25]

So you are using the aftermarket mechanical oil pressure gauge instead of the dash gauge? Or are both working? Some aftermarket gauges can get flaky as they get older.

That temp reading makes sense at idle with a 180 degree thermostat, but the highway reading should be similar, or even lower.

Your 210 temp reading on the highway is not going to hurt the engine, but it usually means your radiator is not working effectively. On the highway you are generating more heat, but also running a lot more air through the radiator ( the fan efficiency is mostly irrelevant at that point ). If the radiator cannot keep up it may be undersized, partially plugged, etc. Retarded timing can also make it run hotter.

I wouldn’t be in a big hurry to work on the cooling system. The solution may be as simple as having the radiator rodded out by a shop, or using a higher capacity OEM radiator. A new aluminum radiator is an excellent choice but will cost more.

 

[84prspctr]

none of the factory gauges are hooked up, the cluster does not work. It is all mechanical gauges, I will pick up a 20 dollar full sweep gauge today. I can’t see oil moving in the line when it says 0. The oil is still crystal clear after 600 miles or so. I looked under the oil fill cap and it didn’t look too bad no real “sludge” at the bottom

 

[84prspctr]

It had ok pressure before I put in the thermostat and water pump

 

[84prspctr]

When I changed the old oil I couldn’t see any metal shavings. There was one small little shaving on the magnetic drain plug

 

[GTX63]

I brought a 78 Chevy with a 305 back to life that had been sitting in a barn (yes, a barn find) for about a decade. 120K on the original motor, granny driven.
After getting it running, I changed the oil with the Rotella 20w 50 stuff.
The oil pressure was 5psi at idle and about 20psi tooling down the road. Not a tick, click, knock, bang or clunk. No smoke, no oil usage. The engine was as quiet as day 1. All I could hear with the hood shut was the clutch fan. I ran a mechanical pressure test and changed out the sending unit. No difference.
The truth is that not a whole lot of oil pressure is needed to keep an SBC lubricated. 5psi per thousand rpm is what I was taught growing up in the 80s.

I would keep the 180 thermostat in the truck. It was designed for it and should have one.

 

[84prspctr]

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[84prspctr]

It looks clean to me