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Engine new, old, miles? 0 is not good. If an old engine, what viscosity oil?

I had an Aerostar and after 90K I had to run 20-50. The oil pump had worn some.

Viscosity helps some, but probably not enough if at 0.

On the stock SBC 20 at idle was common.
 

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My oil pressure at idle is 25psi.Something is wrong :confused: Keep troubleshooting....don't blow up your motor :eek: bm
 

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Rice Killer said:
when my motor is warmed up my oil pressure reads just a hair over 0 at idle but at 2500 rpm (for instance) it reads over 50psi.

Is it ok to run like this?

I have heard that even as low as 7psi at idle is plenty...I however would be very concerned about mine if I only had 7psi at idle...all I can say is "Houston we have a problem". Is this a fresh motor? What weight of oil are you running? are you sure the guage is accurate? :)
 

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What make and model OP guage do you have? It sounds like you have the plastic capillary. Those are on the economy guages but you can buy the kit from autometer. Our Pontiac had that type of line on autogage brand guage but we redid the dash and switched to the model one step below liquid filled which has steel braid. Anyway the movement on the pressure gauge is called a D'arsenval. Made of brass, it looks like a coiled tube. As pressure increases, the coil unwinds moving the indcator needle. Air is far more compressible than oil. Bubbles will throw it off. Burp the line and see if it helps. Also don't neglect the other replies. All of them bring great things to consider. By the way, how is hok paint to work with? Your car reminds me of the old silver mint that mine was.
 

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Jeffblk72 said:
. Air is far more compressible than oil. Bubbles will throw it off. Burp the line and see if it helps.
.
Air is more compressable than oil is correct but once the pressure stabilizes it will read correctly even with air in the line. It will be slower to reach
pressure and will show pressure longer when the engine is shut off until the air pressure bleeds off but the end result is the gauge will read correctly under operating conditions even with air in the lines.
 

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You've probably overcrimped the little brass ferrule under the tube nut.

You'll need to get a new one from Home depot and try again
 

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I had to switch over my mega-mile, beat to death, almost impossible to kill 307 to 50W20. It read 0 psi at idle after getting off the highway or driving at a constant rpm for awhile. With the thick oil I have about 15-20 psi at idle. All better:).

Kev
 

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wskaiser said:
Air is more compressable than oil is correct but once the pressure stabilizes it will read correctly even with air in the line. It will be slower to reach
pressure and will show pressure longer when the engine is shut off until the air pressure bleeds off but the end result is the gauge will read correctly under operating conditions even with air in the lines.
Pressure is pressure in a dial guage.You are not compressing the oil nor the air,(compressing liquid would be an ugly situation,if possible at all).
 

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keithsixty3 said:
Pressure is pressure in a dial guage.You are not compressing the oil nor the air,(compressing liquid would be an ugly situation,if possible at all).
You have described in better words what I was trying to say but I still say the air in the line is compressed equal to the oil pressure in the line. That is why the gauge response is delayed if there are air bubbles. It takes a while to compress the air on startup and a while for the pressure to bleed off at shutdown, short as it may be.
 

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In the low pressure world of cars, I'll give you the guage pressure is just that, but air will tend to take up fluctuations (needle twitch). In the area of thermodynamics, I wouldn't stick my neck out and make a statement like that. Sorry, my b.s. in mechanical engineering and FAA mechanic license are showing. As far as fluids go, I wouldn't test that pressure is pressure regardless of medium idea with brake fluid. You'd be suprised how hydraulic fluid boils in a mini cup car or aircraft hydraulic system with just one little biddy bubble.
 

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Before you make any major changes like 50 weight oil, you might just want to remove the plastic line from the gauge and see if it is open. I'll bet it's crimped nearly closed. This is very common with plastic and copper 1/8 lines.
Check the easy things first.
 

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If you are sure the gauge and line are fine then your bearings are probably worn out.
 

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novaboy009 said:
I had to switch over my mega-mile, beat to death, almost impossible to kill 307 to 50W20. It read 0 psi at idle after getting off the highway or driving at a constant rpm for awhile. With the thick oil I have about 15-20 psi at idle. All better:).

I have had a similar experience. I built a mild bracket engine with very loose bearing clearances (.0035 rods and .004 mains). I was making use of some parts that were worn and since I was building it for myself I knew there would be no panic or complaints. It was fine on the dragstrip since the engine was started cool and then cooled off after ever run. I eventually put the engine in a street car and had 5 psi oil pressure at idle and 30 psi at 2500 rpm when the car had warmed up to 180 degrees. This was with 10-40 oil. The engine also had a standard oil pump and did not have a high pressure spring. I changed the oil to 4 quarts 20-50 and one quart Lucas. The idle oil pressure went to 22 lbs and the driving speed pressure was 45-50 at 2500-2800. I knew nothing was wrong with the engine except being to loose in the bearing clearances. I put almost 5000 trouble free miles on it before I changed it out to another engine. If you have cut your filter apart and did not find metal particles and residue the oil change is the cheapest and simpliest way to increase pressure. I DO NOT WANT TO TELL YOU TO DO THIS AND THEN SOMETHING BREAKS AND BLOWS UP BECAUSE OF MECHANICAL PROBLEMS. DO THIS ONLY IF YOU THINK THERE IS NO MECHANICAL DAMAGE IN YOUR ENGINE.
 

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Jeffblk72 said:
In the low pressure world of cars, I'll give you the guage pressure is just that, but air will tend to take up fluctuations (needle twitch). In the area of thermodynamics, I wouldn't stick my neck out and make a statement like that. Sorry, my b.s. in mechanical engineering and FAA mechanic license are showing. As far as fluids go, I wouldn't test that pressure is pressure regardless of medium idea with brake fluid. You'd be suprised how hydraulic fluid boils in a mini cup car or aircraft hydraulic system with just one little biddy bubble.
Pressure is pressure period.Your statement about compressing oil and air was inaccurate.Even in hydraulics arent you pumping the fluid to increase the pressure.Liquid+compression,nasty.I know all about needle fluctuation,I work with it every day.Speaking of hydraulics,we have recently switched over to a synthetic oil that resists those evil temptations of boiling.It also has an increased run life,probably costs triple the amount of the organic based oils.
 

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Paul Wright said:
If you are sure the gauge and line are fine then your bearings are probably worn out.
Both ends of the line are fine. I dont know if the gauge is fine, "its auto gauge".

Old School:

What lucas oil product did you use?

I'll cut my filter after work today and tell you what I see.
 

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Rice Killer,
The bearings seem to be it. You may want to go with autometer. If the oil gets too hot (need oil temp guage to know for sure), you may want to consider a cooler. Your machine shop may have used their judgment in place of yours if you specified a set of tolerances when they bored, sold you bearings, ect.

For the rest of you
I am not going to argue. By the same token, I was looking at the accuracy in the guage, not its precision, and I don't ever come out and say "you're wrong" without checking what exactly a reference point is. Ten pounds by a certain guage is ten pounds, however is it ten pounds by standard? He could have five at idle and fifty-five at 2500. I can mash on a brake pedal with the same force, exerting the same pressure and have good brakes or little, depending on if there is air in the system and other little things like cylinder sizes and displacements. Isn't it great that auto manufacturers and some aftermarket vendors and machine shops, do things for us and sell us parts designed for their purpose, doing all of the brain work for us so that we don't have to?
 

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Rice Killer said:
So do you guys think that if I put new rod bearings and main bearings in, my pressure should be good?
Have you tried a different gauge? You realy need to hook up a manual gauge to rule out your gauge or the sending unit as the culprits.
 
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