Think I should clean the oil pump screen?

[85_Olds_Ciera]

Man that article is way off on oil pressure.
RE:
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Engine Oil Pressure
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Oil Pressure should be 25-40psi at 1000rpm and 45-55psi at 2000rpm. Minimum oil pressure should be 15psi at 1000rpm and 30psi at 2000rpm. If this is not the case clearances betwen the bearings and crankshaft journals are excessive. Pressure should be checked only when the engine is warmed-up.

At 1,000 RPM Hot...the 25 psi may be a valid number...I have not checked this RPM...but off idle, my oil pressure does pick up quickly.

>45-55psi at 2000rpm

This is within the range I am seeing (*45*) at 2100 RPM HOT...but I feel this new Milling pump's bypass circuit is kicking in...since even if you take it up to 4,000+ RPM...it's still *45* psi.

>Engines don't need enormous amounts of pressure.

True...when enough bearing surface area exists...

My 855 Cumins (N14) maxes out at 45 psi Hot at 2100 RPM; that's the way they designed it to save fuel in 1994...at idle, they allow 10 psi on the low side....at 1,000 RPM, its up to 30 psi.

Gas engines, if enough bearing surface area exists, don't need much for lower horsepower applications. My in-law's 1 ton 4x4 has around 45 psi hot at idle...if I recall the conversation correctly

[85_Olds_Ciera]

Man that article is way off on oil pressure.

1988 Chevrolet Owners Manual: Beretta

Readings of 205 to 275 kPa (30 to 40 psi) may be considered normal during moderate road speeds of 55 to 60 km/h (35 to 40 mph) with the engine at proper operating temperature. If equipped with the optional LB6 engine (engine Code W), the oil pressure reading could be extend an additional 10 psi (70 kPa) higher under the same operating conditions described above.

But again, the OEM pump had its spring set at 70 psi (Code W: LB6)...but this Milling Oil Pump blows at 60 psi. Hence, unless an OEM pump was installed...who knows to be exact on readings.

[geoffinbc]

The bypass is NOT temp dependent. It is just a spring and piston.

Oil pressure has no correlation with bearing surface. If an engine is requiring large amounts of pressure to stay alive it is like that because it needs that much flow. If you want more flow through the same hole then the pressure increases accordingly.

[85_Olds_Ciera]

The bypass is NOT temp dependent. It is just a spring and piston.

From 2100 RPM onward with motor up to temp....same old reading with this new pump.

Logically, it points to a temp/by-pass relationship...as the temp rises, the by-pass set point lowers.

When springs get hot...their elastic property increases...which decreases set-point.

It has a violet colored spring in this Milling pump...but I could not get any tech info from their site.

This is what I observe....with motor up to temp....no increase in oil pressure past 2100 RPM.

PS: Have they re -engineered these pumps? As I noted, Cumins uses 45 PSI max on N14 motors....I talked to an engineer there...I know this...

[85_Olds_Ciera]

If an engine is requiring large amounts of pressure to stay alive it is like that because it needs that much flow.

How Much Oil Pressure?

Vehicle manufacturers have traditionally recommend a minimum of 10 psi of oil pressure for every 1,000 rpm of engine speed. Using these numbers, most stock engines don't need any more than 50 to 60 psi of oil pressure. With tighter bearing clearances, pressure goes up requiring less flow from the pump and less parasitic horsepower loss to drive the oil pump. In racing applications, the old school of thought was more oil pressure was needed to keep the engine lubed. That's true if bearing clearances are loosened up. But most engine builders today tighten clearances so less oil flow is needed to maintain adequate oil pressure. This approach increases the horsepower output because less power is needed to drive the pump at high rpm.

A stock oil pump is usually more than adequate for most street performance engines, and even many racing engines. NASCAR engines typically get by just fine with no more than 50 psi of oil pressure at 9,000 rpm!
....
...

[85_Olds_Ciera]

The bypass is NOT temp dependent. It is just a spring and piston.

If this is true...then I have no idea what is going on...

[85_Olds_Ciera]

Also 5W30 and 10W30 are the exact same Viscosity at 200*F.

Interesting chart here on second page...notice the sentence above the chart:

Figure 2 shows the sensitivity of oil viscosity with changing temperature. The viscosity change as a function of temperature is a huge factor in regulating the
flow with a pressure reactive device.

[geoffinbc]

Precisely. And oil is rated just the same The first number you read 0 5 10 or 20 is a crank rating for the oil. Basically at cold temp the higher the number the thicker it is. Your second number is your oil viscosity at 100*C. 10 15 20 30 40 50 and so on, automotive oils rarely go above 70 most oil above 30 are for air cooled or racing engines.

If you are getting a huge oil pressure spike during cold operating temperature then you may be exceeding the pressure relief capacity. It is common practice to increase the relief orifice on pumps that are modified with larger pickups or high volume. If you bought a Melling HV pump this may be the case. It may still be true on a stock pump and a high crank rated oil. Try the 5W you may see a difference.

The last piece of advice is NEVER trust the stock gauge. If you truly want to know your oil pressure you need a mechanical gauge or accurate electric gauge (like an Autometer) with pressure taken on the return side of the oil filter, after oil has passed the filter and is about to enter the main entrance gallery up to the oil passages above the cam.

[85_Olds_Ciera]

Melling HV pump this may be the case.

2.8 Engine: Melling M-95B: Melling stock replacement oil pump to fit GM cars & trucks, Jeeps and Isuzu's with the Chevy 2.8L(173ci) and 3.1L(189ci) engines in the following applications;

The last piece of advice is NEVER trust the stock gauge.

I'm fully aware....and am aware my bench test of "calibrating" digital dash readout to air pressure applied to Oil Sender Unit is not perfect.

Tonight, I have sent an email to Milling Tech Support....to find out if ByPass Circuit is temperature dependent or not.


From one of your previous posts here:

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Posted: 11-26-2006, 01:04 PM
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A member on S-Series used an HV pump on his blown 4.3L build. The engine lasted only a few thousand miles before it ate itself. The problem ended up being the HV pump which was causeing excess airation in the oil.

Do not overlook Oil Screen: here's a tech note from Milling. A bad screen could create the same type of effect...all depending.

Further, screens come in different cross-sectional areas; on the 3.8 motor I put back together, it used a fine mesh screen, whereas this 2.8 uses a coarse screen.

[geoffinbc]

Well the screen causing a failure is a long shot. And the HV pump was observed to be the killer of the 4.3L motor. The bubbles in the oil could be seen clearly on the dipstick even when the motor was off.

[85_Olds_Ciera]

...bubbles in the oil could be seen clearly on the dipstick even when the motor was off.

Unless the parts were examined (oil pump..block), its speculation...Points:

1. Was the Screen placed in correct position? When I put in new pump recently...I made sure it was in same position when I took it out...and spot welded tube to pump after this check.

2. If Screen got plugged, or was not the right screen (too small) could the pump suck air where tube inserts into oil pump?

3. Was the pump's mating surface flat against block...no warpage/etc.

If your engine is tight...there's no need for a High Volume pump...I would agree with you on this point...but with loose clearances, a HV would be OK.

Btw, does the 2.8 engine have a plugged oil port on block/heads that I could get a direct reading?

I have this feeling the OEM digital Oil Sender is not in a choice location...the response lags.

[geoffinbc]

Almost all our engines use a port on the oil filter adaptor.


Take a look at these 2 adaptors one is an s-10 and one is a Camaro (black). The pressure is read right as the oil enters the block. This is the ideal location for measuring the pressure. The S-10 adaptor actually has 2 locations. This is left over from when the trucks used to have a seperate guage sender and oil pressure switch which send 12V to the fuel pump. On the newer models the guage and switch were all in one. Your vehicle should use a similar adaptor. If I remember (havent looked in a while) there is a plug in the block near the filter mount that will serve the same porpose. Check it out it will be easy to spot.

[85_Olds_Ciera]

If I remember (havent looked in a while) there is a plug in the block near the filter mount that will serve the same porpose. Check it out it will be easy to spot.

On 1988 2.8 installed in Beretta...now that I think about it....on block side, there is an individual cavity (port) with I think it has a check ball within it...and behind check ball is where Oil Sender is connected on block side.

I had the adapter off...and should have got my glasses...but thats what it looked like...and the adapter had a separate cavity that fed this Oil Sender circuit for oil going to engine (filter's output side).

I guess I will have to put a T line in with sender...what a pill...to do it right and clean gasket off...off comes starter and AC compressor...then you can see it all clearly.

thanks...

[85_Olds_Ciera]

Engines don't need enormous amounts of pressure. They just need a constant non failing supply of oil.

Tidbit: THE 3.4 DOHC 24 VALVE

The 3.4L DOHC motor was designed....Revamped oiling system with high volume pump. An oil cooler.

[geoffinbc]

Well take that statement lightly. It said the 3.4L has a forged crank and pistons. All wrong information.

I am not sure what pump is actually in the DOHC motor but a simple P/N cross reference will tell you.