25 replies to this topic

[cian]

Hey guys what oil pressure is "normal" at idle?  I'm just finished a rebuild with an sw8 cam and it idles at 20psi drives at a steady 50 psi 

[dklawson]

There is no carved in stone value in spite of what you may find posted.  The oil pressure will be a function of the engine condition, the grade of oil you are using, the engine operating temperature, and the engine idle speed.

 

That being said, for a freshly rebuilt engine 20 PSI is very low.  What was replaced during the rebuild and what was not replaced (oil pump, bearings...)?

[pusb]

Mine idles at about 70 when cold, then 50 when warm (although after a high speed run it can drop as low as 35 for a few minutes)

 

Driving it is normally between 60 and 75 hot and cold.

[cian]

All bearings where replaced and the pump too

[Gremlin]

20 is too low for a full engine rebuild, have you altered the relief valve at all? and what oil are you using?

[Gr4h4m]

I would check the relief valve first

[dklawson]

I agree, the relief valve may be stuck open or not fully closing because of swarf.  Hopefully that is all it is.

[Morry Stu]

My 948 runs at 20psi idle 45psi hot.

Has done for 30 years. Has never changed despite 2 full rebuilds.

You dont need super high pressure.

[Captain Mainwaring]

I think you may be surprised at just how inaccurate the gauge may be

[Morry Stu]

My gauge is spot on. Had oil pressure checked with calibrated workshop gauge recently. Its also had a new gauge. All have had the same readings.

I only use mechanical guages like Speco or VDO

[BKozan]

I agree, 20 is a bit low. 

 

Mine idles at about 70 when cold, then 50 when warm (although after a high speed run it can drop as low as 35 for a few minutes)

 

Driving it is normally between 60 and 75 hot and cold.

 

My Rover is exactly the same - 70 cold idle, 50 warm idle and 60-75 driving. I am very, very curious though, why is it, that after an hour of freeway driving the oil pressure drops down to 35-40 for 15 minutes? The only possibility I can come up with is "thinning" of the oil itself, but I am wondering if anyone has a firm answer on this. 

[pusb]

I agree, 20 is a bit low. 

 

Mine idles at about 70 when cold, then 50 when warm (although after a high speed run it can drop as low as 35 for a few minutes)

 

Driving it is normally between 60 and 75 hot and cold.

 

My Rover is exactly the same - 70 cold idle, 50 warm idle and 60-75 driving. I am very, very curious though, why is it, that after an hour of freeway driving the oil pressure drops down to 35-40 for 15 minutes? The only possibility I can come up with is "thinning" of the oil itself, but I am wondering if anyone has a firm answer on this. 

 

I asked the question on here before, and apparently its just that after a long fast drive the oil is very warm and, like you say that causes it to thin out.

[Morry Stu]

Hey guys what oil pressure is "normal" at idle?  I'm just finished a rebuild with an sw8 cam and it idles at 20psi drives at a steady 50 psi 

I would be perfectly happy with that. They come out of the factory at 40-50psi.

[Morry Stu]

I agree, 20 is a bit low. 

Why do you think its to low. ?

[cian]

Hi I'm liking the responses guys I'm using a scrappy halfords mineral oil to run it in,  and I'm just running the standard bullet relief valve 

Edited by cian, 05 June 2014 - 06:58 AM.