Oil Pressure
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Oil pressure is caused by resistance to the flow of the oil. If there is little flow, because of excessive clearances in the pump, the pressure will be low. Likewise, if there is little resistance to the flow, pressure won't build up. The very FIRST step, is to verify the oil pressure readings, by hooking up a known good, mechanical, oil pressure gauge. You make no mention of the year, mileage, or general condition of the engine. That oil pressure isn't so awful. What are the (true) readings at higher rpms? You could try a thicker oil and see what happens. Again, it is difficult to make recommendations with so little information. An age old, and still good, rule of thumb, is approx 10 psi of oil pressure for every 1000 rpms. Even 4 psi at a 6-700 rpm idle isn't too far off.
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Thread Starter
Burning Brakes
Joined: Jan 2005
Posts: 1,217
Likes: 0
From: Augusta GA
Originally Posted by CFI-EFI
Oil pressure is caused by resistance to the flow of the oil. If there is little flow, because of excessive clearances in the pump, the pressure will be low. Likewise, if there is little resistance to the flow, pressure won't build up. The very FIRST step, is to verify the oil pressure readings, by hooking up a known good, mechanical, oil pressure gauge. You make no mention of the year, mileage, or general condition of the engine. That oil pressure isn't so awful. What are the (true) readings at higher rpms? You could try a thicker oil and see what happens. Again, it is difficult to make recommendations with so little information. An age old, and still good, rule of thumb, is approx 10 psi of oil pressure for every 1000 rpms. Even 4 psi at a 6-700 rpm idle isn't too far off.
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Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
I generally don't look where someones home town is supposed to be for car info. Most people will give the car and engine info in the text with the problem. Also, I didn't see 50,000 miles or 383 listed as part of where you live. Although you didn't say (there is SO much you didn't say) I thought you were talking about idle pressures. Step one, above, is still valid. If the pressure IS that low, you have serious problems, and they aren't likely to be the oil pump.
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Thread Starter
Burning Brakes
Joined: Jan 2005
Posts: 1,217
Likes: 0
From: Augusta GA
Originally Posted by CFI-EFI
I generally don't look where someones home town is supposed to be for car info. Most people will give the car and engine info in the text with the problem. Also, I didn't see 50,000 miles or 383 listed as part of where you live. Although you didn't say (there is SO much you didn't say) I thought you were talking about idle pressures. Step one, above, is still valid. If the pressure IS that low, you have serious problems, and they aren't likely to be the oil pump.
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Le Mans Master
Joined: Jan 2002
Posts: 9,036
Likes: 13
From: Edmonton AB
Originally Posted by red_johnny
You say serious problems but you don't say what they might be.
First check whether the gauge is accurate - sometimes senders or
gauges go bad and display faulty readings.
If a test (see above) proves that pressures are as low as 4-10 psi
at higher RPM then somewhere in the engine, clearances have
enlarged to such an extent that the pump can not keep up with the
leakage through the clearances. Or the pump itself has become worn
and is unable to generate enough pressure.
The head gasket is not usually implicated in low oil pressure issues.
.
Thread Starter
Burning Brakes
Joined: Jan 2005
Posts: 1,217
Likes: 0
From: Augusta GA
Originally Posted by Slalom4me
Read CFI-EFI's comments again.
First check whether the gauge is accurate - sometimes senders or
gauges go bad and display faulty readings.
If a test (see above) proves that pressures are as low as 4-10 psi
at higher RPM then somewhere in the engine, clearances have
enlarged to such an extent that the pump can not keep up with the
leakage through the clearances. Or the pump itself has become worn
and is unable to generate enough pressure.
The head gasket is not usually implicated in low oil pressure issues.
.
First check whether the gauge is accurate - sometimes senders or
gauges go bad and display faulty readings.
If a test (see above) proves that pressures are as low as 4-10 psi
at higher RPM then somewhere in the engine, clearances have
enlarged to such an extent that the pump can not keep up with the
leakage through the clearances. Or the pump itself has become worn
and is unable to generate enough pressure.
The head gasket is not usually implicated in low oil pressure issues.
.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
I told you how oil pressure is developed. I told you what the next step is. How much dumber do you want me to dumb it down? 'Splain to me the relationship between oil pressure and the head gasket.
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Le Mans Master
Joined: Jan 2002
Posts: 9,036
Likes: 13
From: Edmonton AB
Don't run the engine much until you can verify whether
the pressures are really that low, certainly do not drive
it anywhere.
Right now you have an engine that MAY be sick but which
is intact and in operational condition. Running it with low
oil pressure can be harmful to your wallet.
Any increase in engine noise as the pressures have been
dropping? How about oil & coolant operating temperature
changes?
.
the pressures are really that low, certainly do not drive
it anywhere.
Right now you have an engine that MAY be sick but which
is intact and in operational condition. Running it with low
oil pressure can be harmful to your wallet.
Any increase in engine noise as the pressures have been
dropping? How about oil & coolant operating temperature
changes?
.
Burning Brakes
Joined: May 2006
Posts: 857
Likes: 1
From: Morrisonville Illinios
THis is real stupid but I am sure you have checked the oil level? But with pressure that low the oil pressure switch should shut the engine down. I would get a mechanical gauge to see what the pressure is at idle. If its that LOW you don't need to go any farther. shut it off and you may want to think about droppin the pan. Pump is not hard to swap out but I think I would look at the bearings and check the them with some plastic-gage. wro87
Thread Starter
Burning Brakes
Joined: Jan 2005
Posts: 1,217
Likes: 0
From: Augusta GA
Originally Posted by Slalom4me
Don't run the engine much until you can verify whether
the pressures are really that low, certainly do not drive
it anywhere.
Right now you have an engine that MAY be sick but which
is intact and in operational condition. Running it with low
oil pressure can be harmful to your wallet.
Any increase in engine noise as the pressures have been
dropping? How about oil & coolant operating temperature
changes?
.
the pressures are really that low, certainly do not drive
it anywhere.
Right now you have an engine that MAY be sick but which
is intact and in operational condition. Running it with low
oil pressure can be harmful to your wallet.
Any increase in engine noise as the pressures have been
dropping? How about oil & coolant operating temperature
changes?
.
Race Director
Joined: Jun 1999
Posts: 14,924
Likes: 9
From: Merritt Ils Fl
The SBC oil pump is about as close as you will ever come to mechanical part that never fails, not much can go wrong with two gears. CFI_EFI is right on in his suggestion about a mechanical pressure gauge check. That will tell you a bunch.
Le Mans Master
Joined: Jan 2002
Posts: 9,036
Likes: 13
From: Edmonton AB
Check for trash in the air intake and/or between the rad & the A/C
condensor. This step should be performed a few times each year.
Use a garden hose to flow water through from the engine compartment
forward or pull the rad and clean in there thoroughly.
Came back from the shop?
.
condensor. This step should be performed a few times each year.
Use a garden hose to flow water through from the engine compartment
forward or pull the rad and clean in there thoroughly.
Came back from the shop?
.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by wro87
But with pressure that low the oil pressure switch should shut the engine down.
For the umpteenth time, there is NO low oil pressure switch on ANY C4!
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Thread Starter
Burning Brakes
Joined: Jan 2005
Posts: 1,217
Likes: 0
From: Augusta GA
Originally Posted by CFI-EFI
Oil pressure is caused by resistance to the flow of the oil. If there is little flow, because of excessive clearances in the pump, the pressure will be low. Likewise, if there is little resistance to the flow, pressure won't build up. The very FIRST step, is to verify the oil pressure readings, by hooking up a known good, mechanical, oil pressure gauge. You make no mention of the year, mileage, or general condition of the engine. That oil pressure isn't so awful. What are the (true) readings at higher rpms? You could try a thicker oil and see what happens. Again, it is difficult to make recommendations with so little information. An age old, and still good, rule of thumb, is approx 10 psi of oil pressure for every 1000 rpms. Even 4 psi at a 6-700 rpm idle isn't too far off.
RACE ON!!!
RACE ON!!!
Thread Starter
Burning Brakes
Joined: Jan 2005
Posts: 1,217
Likes: 0
From: Augusta GA
Originally Posted by kopbet89c4
Valve rattle? 245-255 degree coolant? Sounds like detonation/pinging to me! My friend overheated his old 305 Silverado and we actually thought of valve rattle.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by red_johnny
So should have the first step been check the oil?
Originally Posted by red_johnny
Let me dumb it down for everyone, if you dont have enough oil in your oil pan then your PSI readings will be lower than normal so first thing you should always check is your oil level.
Originally Posted by red_johnny
See I got a high performance 383 stroked engine with piston rings that allow oil seepage. So basically every two weeks 1 quart of oil passes through and gets burnt off.
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Thread Starter
Burning Brakes
Joined: Jan 2005
Posts: 1,217
Likes: 0
From: Augusta GA
Originally Posted by CFI-EFI
And every two weeks you scratch your head and wonder what could be the cause of the oil pressure dropping off like that... again. Where can I get some of them high performance, stroked piston rings that allow seepage like that? I bet that keeps them from rusting.