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oil pressure question

Huicho417

Huicho417

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I recently added an electronic Bosch oil pressure gauge to my 67 Coronet, where before it only had the sensor light. What is the proper oil pressure at idle and when the car is running? I have noticed that when I first start the engine its at about 35 to 40 then gradually goes down as the engine warms. My worry is that it goes down to about 10-15 psi, but does go up as i increase speed. The only point of reference I have is my 2014 truck which is constantly at 40 psi. The sensor light has never turned on, except when I initially turn the key. Then turns off when the engine starts. But I am sure they are two completely different systems.
 
An older street engine will idle quite happily at 10 psi. And 40 is OK.
If there are no knocks/rattles nothing to worry about.
Do not batter it too much it will probably run for years, might be a problem however if you try some racing.
I assume the engine is old??and stock??
 
Id say that 10-15 PSI @ idle would get my attention, but if it is not rattling and the pressure goes up and holds as the RPM goes up you are probably ok. Might try a little thicker oil to see if it goes up a little. Generally I want to see north of 25 at idle at least but I have had cars that had pretty low pressure that ran fine, usually these were high mileage motors.
 
It sounds just fine. Cold oil makes more pressure. More rpm makes more pressure. 10-15 at idle on a warm used engine is just fine. You didn’t know anything without that gauge. Was it working fine before? Is it working fine now?
 
Huicho417 said:
I recently added an electronic Bosch oil pressure gauge to my 67 Coronet, where before it only had the sensor light. What is the proper oil pressure at idle and when the car is running? I have noticed that when I first start the engine its at about 35 to 40 then gradually goes down as the engine warms. My worry is that it goes down to about 10-15 psi, but does go up as i increase speed. The only point of reference I have is my 2014 truck which is constantly at 40 psi. The sensor light has never turned on, except when I initially turn the key. Then turns off when the engine starts. But I am sure they are two completely different systems.
Click to expand...
Most stock pumps do around 30-40 psi I run 50 at idel in a 360 jeep and 75 on the Charger most of the oil warning red lites are set around 15 positive oil pressure is a must there is lots of room for discussion. I do my oil changes by the pressure . Oil is the liquid ball bearing between surfaces . Sloppy is fast as long as you have the pump to back it up.
 
I actually took the engine out several months ago and gave it a major overhaul with exception of removing the pistons, crank and cam. When I took delivery of the car it sounded great so I felt like it did not need that messed with. I did rebuild the heads, cleaned out the water jacket, replaced expansion plugs, new water pump, new starter, new alternator and so on. I went home during my lunch break and let it idle for a bit and it stayed at 45 oil pressure. It must have been after I ran it for a while that I noticed it go down to the 10-15 psi.

The car idles and sounds great with no engine noise at all. I also checked engine vacuum and it stayed steady at 20 inches of mercury. Kinda sounds like I may be worrying over nothing. Thank you everyone for the feedback!
 
Problem is we dont have enough info about your car or motor to know if you may have an issue, as others have said, a little oil pressure is enough at idle, with no load on engine. However, bear in mind, one of the main reasons for low oil pressure is worn pump...... a much more prevalent cause of low pressure is worn main and rod bearings, as it dumps right back into the pan before getting much up top..... If you still have enough pressure at load to overcome loss and lubricate the valve train, then you are fine.

***EDIT*** Reading the above post, I'd say you have no worries....
 
Lefty71 said:
Problem is we dont have enough info about your car or motor to know if you may have an issue, as others have said, a little oil pressure is enough at idle, with no load on engine. However, bear in mind, one of the main reasons for low oil pressure is worn pump...... a much more prevalent cause of low pressure is worn main and rod bearings, as it dumps right back into the pan before getting much up top..... If you still have enough pressure at load to overcome loss and lubricate the valve train, then you are fine.

***EDIT*** Reading the above post, I'd say you have no worries....
Click to expand...
You know your stuff so if a motor is built with .001 on the mains and rods for clearance thats the best? Or do you do .003 with a high volume oil pump and thicker oil?
 
You don’t need a hi volume pump with .003 bearing clearance. And it’s not good to have .001 bearing clearance. It depends on the diameter of the journals also.

the oil gets hot from driving and loading the engine, sitting at idle doesn’t really get it hot, the coolant will be hot.
 
440 Charger said:
Or do you do .003 with a high volume oil pump and thicker oil?
Click to expand...

A loaded question lol.... When building up a motor I consider it's use, and build to the tighter side of factory spec if it's a normal rebuild, when setting the bearings and the (if file fit) rings. If the use is special, I work with my machinist for any special considerations... I do usually use a HV pump for a hipo motor, and for a summer use race motor we will use 20w50 oil. However, on the subject of oil, be wary of using heavier oils in a worn engine that starting to burn oil.... they are stickier, and they will actually encourage further oil burning as such and will lead to heavy deposits even faster.... the rings and valve seals will suck heavy oil easier than a light oil due to the fact that it sticks to the valves and cylinder walls better than a standard oil.
 
Lefty71 said:
A loaded question lol.... When building up a motor I consider it's use, and build to the tighter side of factory spec if it's a normal rebuild, when setting the bearings and the (if file fit) rings. If the use is special, I work with my machinist for any special considerations... I do usually use a HV pump for a hipo motor, and for a summer use race motor we will use 20w50 oil. However, on the subject of oil, be wary of using heavier oils in a worn engine that starting to burn oil.... they are stickier, and they will actually encourage further oil burning as such and will lead to heavy deposits even faster.... the rings and valve seals will suck heavy oil easier than a light oil due to the fact that it sticks to the valves and cylinder walls better than a standard oil.
Click to expand...
I would type you know your stuff. These thing were all figured out before Mopar recommends straight 30 oil for mine.
 
Huicho417 said:
.....................and gave it a major overhaul with exception of removing the pistons, crank and cam.
Click to expand...

I would consider calling what you did "freshened up the heads", and maybe not calling it a major overhaul.

None the less, good for you. You need to start somewhere.

10 psi is fine. And, if its an electric gauge, I would not even bet its correct.
 
Of course one could refer to the FSM.
An example from the 1970..........

upload_2021-5-26_7-22-17.png

upload_2021-5-26_7-12-40.png
 
Daves69 said:
Of course one could refer to the FSM.
An example from the 1970..........

View attachment 1115179
View attachment 1115174
Click to expand...
Very nice and true. Seems to me if you have positive oil pressure you are probly ok. Over 100 pops seals flow is the key sloppy is fast. Easy way to tell if you need an oil change see what pressure you have at idle with motor hot say its 45psi when it drops after a few thousand miles the oil has thinned.
 
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