Adjusting Oil Pressure

First some history, and then a little tech.

I've just replaced the spring in my oil pump.

I had a high volume pump which gave me about 35 PSI of oil pressure
at ~900 RPM and 60 PSI by 3500 RPM.

Once the pressure hit 60 PSI on the gauge at 3500 RPM, "SOMETHING"
limited the pressure to 60 PSI as the RPM of the motor raised from
3500 to 6000 RPM.


The new spring (Black) allows for 60 PSI cold up to about 5500 RPM and 20 PSI at 900 RPM.

Once the engine is warm, the pressure "LIMITS" to 40 PSI at
3500 RPM. As the motor raises above 3500 RPM, the pressure
drops to about 30 PSI and climbs back to 40 PSI...it never exceeds
40 PSI.

My questions are:

1. How much oil pressure is adequate for 6000 RPM? This is a street/strip
motor. I use 10W30 motor oil.

I've always been told that 10 PSI per 1000 RPM is the rule.

2. Should I return to the high pressure spring that limits 60 PSI
from 3500 RPM upward to 6000 RPM?

3. What is regulating the pressure? Is it the valve in the oil pump,
or the adapter at the oil filter?

4. Lastly, if I use the high pressure oil spring, is any oil getting
bypassed around the filter once the pressure is limited to 60 PSI,
or does it flow back into the oil pan? What and when does the
spring open in the device located at the oil filter adapter?

I've tried researching the oil circuit and protection devices, but
I'm coming up with vague information.

Tomorrow I'd like to drop the oil pan to fix a leak and adjust the oil
pump pressure while I'm in the process.

Some pros and cons for high volume pumps, as well as oil circuit protection
devices would be awesome!

Just so you don't think I took the easy way out, here are my
findings:

1. I was told 10 PSI per 1000 RPM

2. Not sure, what is the difference?

3. I believe the valve in the oil pump is regulating the pressure.

4. The relief valve in the oil filter adapter only opens once there
is a block in flow. The pressure differential between the spring
in the adapter and the oil circuit must be at least (xxx PSI) before
the bypass circuit is active.

I am guessing this bypass circuit opens once the pressure differential
reaches about 35 PSI (60 PSI of filter flow plus 35 PSI of pressure "back up").

10 psi per 1000 rpm is normal but also excessive. A pump trying to produce 60 psi at 6000 rpm is using up a lot of HP doing it. A maximum of 40 psi is all that's required and 10 psi at idle is fine.

Pressure is just an indication of how tight or loose the internal parts are. The key is to have volume. You want the pump to push as much oil through the system as possible to keep everything lubricated. If pressure is too high then there's restriction somewhere. Too low and oil is flowing out somewhere too quickly. Think of a garden hose. A half inch hose free flowing could probably fill a bucket in about a minute but there's little pressure. Cover part of the opening with your finger and you increase the pressure but it should still fill the bucket in roughly the same time.

The old trick for pumping more oil is to use a BBC pump on a SBC. They're interchangable but the BBC pump pushes more oil. A SBC pump has 4 bolts on the pump cover. The BBC pump has 5.

Originally posted by Stephen 87 IROC
[BThe old trick for pumping more oil is to use a BBC pump on a SBC. They're interchangable but the BBC pump pushes more oil. A SBC pump has 4 bolts on the pump cover. The BBC pump has 5. [/B]
I thought thats what most "high volume" pumps were. Basically just big block pumps with screens to fit small block pans? (in reference to the basic Melling or Speed Pro pumps)

Becuase, before the M55-HV, wasn't the M77 what was used?

Personally I would go to a regular volume pump with a high pressure spring. The GM white spring is a good one to use.

Good article on oil pumps.

http://www.stockcarracing.com/techarticles/134_0309_pump/

Should answer many of your questions.

-Mindgame

Nice! What a great article.

Thanks for all of the replies everyone. My assumptions have been
confirmed - and then some!

You don't realize the impact on the ignition even though the distributor
is driven from the same point.

Cool stuff!

Now I just have to get my head around watching the oil gauge
sit at 30 PSI @ 6000 RPM.

It will be a big psychological hurdle to over come. I'm sure the
paranoia will set in for a while :)

Originally posted by Zero_to_69
Now I just have to get my head around watching the oil gauge
sit at 30 PSI @ 6000 RPM.

That's easy. I don't even watch mine. Right beside it I have a 2" round red clearance light mounted in the dash. I would have used a 4" round tail light but there wasn't enough room to mount it. It's connected to another sensor on the block. When oil pressure gets below 5 psi, the big red light comes on. That's the only time I worry.

One race I crossed the finish line and the light was flickering. I quickly glanced at the gauge and it said I still had good pressure. I came back up the return road and the light was still flickering but pressure was good. I use a mechanical gauge. When I got back to the pits I found the wire at the sending unit for the light fell off. It provides a ground and was brushing up against the header creating a ground and making the light flicker.

I use both the pressure gauge and warning light but rely more on the light. It's hard to watch gauges while going down the track but when a big red light comes on, you can't miss it.

I just finished reading that article. Just about mentions everything I said in my above post :)

Another trick to do is to use a larger capacity oil pan but don't use the extra oil. The engine only needs to have enough oil to keep everything lubricated so only a minimum of oil is needed in the pan. I use a 7 quart pan on my BBC but keep it at the ADD level. This still allows plenty of oil to cover the pickup plus it keeps the oil below the crank and windage tray. The baffels in the pan keep the oil in the sump during hard launches and decelleration. There are even some racers that only keep 3 quarts in the pan.

The block can also be modified for better oil control. SBC require the drain holes in the lifter valley to be plugged which will force the oil to return to the front of the block and drain into the timing chain area. This keeps the oil from draining down onto the crank causing windage.

I meant that quote more to mean, I'm accustomed to seeing
50 PSI @ 6000, not 30 PSI.

I don't want it to freak me out once I glance down and see the
new reading.

That's a good idea about the warning lamp. I guess it wouldn't
take much to screw in an electric sender and wire up a light.

As for my only unanswered question: When/How does the relief
valve in the oil filter adapter come into play?

How much pressure is required to open that valve? 100 PSI? 5 PSI?

Does it partially open under high pressure oil pump action?

What if the filter was totally plugged, how sensistive is that bypass
valve to allow unfiltered oil to the engine?

Are you picking up what I'm putting down? :)

From a GM service manual

"Oil enters the pump through a screened inlet located near the bottom rear of the oil pan. The pressurized oil from the pump passes through the oil filter. The oil filter base has a by-pass valve which, in the event of filter restriction, will open at 5.5 to 6.5 psi."

Oil flowing through the filter although it's pressurized, it's unrestricted. The by-pass valve is actually looking for backpressure. If the outlet pressure is less than the inlet pressure then there must be a restriction in the filter and the by-pass opens. It's just a simple valve with equal oil pressure on both sides. When the outlet side pressure drops, the valve opens. Newer vehicles with a factory oil cooler have a similar system but it's set at around 12 PSI difference. If the cooler plugs and the pressure drops more than 12 psi, the oil is by-passed around the cooler.

Something like the brake pressure differential valve. When brake pressure is the same on both sides there's no fault. Lose pressure on one side and the valve moves over, completes a curcuit and turns on the brake warning light.

Generally,and I mean generally,40PSI will be good enough out the back door.It has to have the volume to produce the pressire.
10psi per thousand RPM's is not needed except on a loose clearanced,8000+RPM,trailer queen or a BB F***If you have a street/strip engine 40psi@ 6000RPM's hot should be plenty.The pump spring is doing all the regulating.

Nice answers guys. That puts a wrap on my 'black box' understanding
of the oil system.

I'm actually impressed that I picked off most of the operating
principals in my second post.

It's so difficult to find good information these days. It's amazing
how many different versions of concept you'll hear by talking to
a handful of people. The sad part is, most of them picked it up
from daddy, or Mr. Dumb's Internet site and take it to the bank.

Thanks for all of your time everyone!

Originally posted by Stephen 87 IROC
I just finished reading that article. Just about mentions everything I said in my above post :)

And then some. :)



System One has a pretty nice, and easily adjustable, oil pump on the market. Not that it's too tough a chore but the price is a little steep.

-Mindgame

Originally posted by Stephen 87 IROC
You want the pump to push as much oil through the system as possible to keep everything lubricated.

I'd prefer it to state push as much oil through the system as NECESSARY. Pushing as much as possible, is too much/overkill. Sounds like to old adage, more is better. In due respect, I find your post contradictory.

Originally posted by Mindgame
Good article on oil pumps.

http://www.stockcarracing.com/techarticles/134_0309_pump/

I read the article through. I find it misleading and contradictory as well. If you can generate pressure, you have adequate volume for the circuit/passages/clearances needing lubing. As noted above, the circuit in question, will determine the pressure generated.

Originally posted by Stephen 87 IROC
I use a 7 quart pan on my BBC but keep it at the ADD level. This still allows plenty of oil to cover the pickup plus it keeps the oil below the crank and windage tray. The baffels in the pan keep the oil in the sump during hard launches and decelleration. There are even some racers that only keep 3 quarts in the pan.

The block can also be modified for better oil control. SBC require the drain holes in the lifter valley to be plugged which will force the oil to return to the front of the block and drain into the timing chain area. This keeps the oil from draining down onto the crank causing windage.

Although I subscribe to these very techniques myself, in fairness, a warning could be attached to these paragraphs to prevent some unwary individual from copying these techniques on their stocker. Depending on pump in use, a qt. low, could be fatal. Even though roller lifters are used, for high mileage expectations, it should be noted, there is no direct lifter/cam lobe lubrication, so this area depends on oil 'splash' for lube. Some of this splash comes from center access holes in block.

Originally posted by Stephen 87 IROC
From a GM service manual, ".....The oil filter base has a by-pass valve which, in the event of filter restriction, will open at 5.5 to 6.5 psi."

The testing I've done, concludes something more like 8.0-8.5#, so, I consider the manual.... ah, close. More in line with what I've read elsewhere.

Newer vehicles with a factory oil cooler have a similar system but it's set at around 12 PSI difference. If the cooler plugs and the pressure drops more than 12 psi, the oil is by-passed around the cooler.

The LT systems I've come across, use the same identical valve/spring assembly in the oil filter differential bypass valve as what is in the cooler adapter. Not able to speak for all LTx vehicles, but would believe they are the same.

Something like the brake pressure differential valve.

I prefer to describe it as a pressure differential bypass valve myself.

Originally posted by 1racerdude
Generally,and I mean generally,40PSI will be good enough out the back door. It has to have the volume to produce the pressure.
10psi per thousand RPM's is not needed.....If you have a street/strip engine 40psi@ 6000RPM's hot should be plenty.The pump spring is doing all the regulating.


I agree with this guy, especially about the "It has to.... pressure".

Originally posted by arnie
I read the article through. I find it misleading and contradictory as well. If you can generate pressure, you have adequate volume for the circuit/passages/clearances needing lubing. As noted above, the circuit in question, will determine the pressure generated.

Alot of stuff there, which part(s) do you find "contradictory" or "misleading" arnie?

That article was obviously a product of interviews with the two engineers from Melling, Mike Osterhaus and Cal Rydjord. So maybe they are "misleading" on purpose or are they unaware of such deeds?

:)

-Mindgame

Originally posted by Mindgame
Alot of stuff there, which part(s) do you find "contradictory" or "misleading" arnie?

That article was obviously a product of interviews with the two engineers from Melling, Mike Osterhaus and Cal Rydjord.

MG, as you stated, the article was not written by engineers. It was written by 'Sleepy' from an interview. IOW, Sleepy's interpretation, and maybe he (Sleepy) was. I'll follow through when more time available.

Originally posted by Mindgame
Alot of stuff there, which part(s) do you find "contradictory" or "misleading" arnie?

That article was obviously a product of interviews with the two engineers from Melling, Mike Osterhaus and Cal Rydjord. So maybe they are "misleading" on purpose....?

In Opening statement

Like other parts in an engine, it can wear out, and it's inexpensive insurance to replace a stock pump.

[Comment #1: so far I agree]

Misleading:

Article omits to clarify there is an association between volume and pressure, in regards to what ends up going thru bearings. Also, written in a way as to put a product in one light (favorable),
and promote that product (hv pump). IOW, article suffers from a conflict of interest.

EXAMPLES:

In Opening Statement

The high-volume pump is designed to pump a higher volume of oil at the same pressure.

[Comment #2: to clarify; hv pump is designed to pump a higher volume, at a given equal specified pressure.]

....it may raise the oil pressure because a higher volume pumped into the same oil gallery space will cause a pressure increase.

[Comment #3: to continue sentence; IF... the volume requirement was higher than a given pump was supplying. IOW, if the volume pumped into gallery space was inadequate, in the first place. If adequate, pressure attained will be equal/limited to what pump was adjusted for.]

Under Heading: Stock Oil Flow

Usually, the bearing clearances are stock. Therefore, even to 7,000 rpm, a stock pump has sufficient volume and pressure to supply oil to the engine.

[Comment #4: This is important to note, cuz this includes 95% of forum members' engines. Know of many engines built with clearances not within the range specified in oem specs?]

Under Heading: High-Pressure Pumps

If this extra pressure is not needed, then the engine is using horsepower to pump oil to a peak pressure that is unnecessary--thus resulting in less power to the wheels. An additional loss is that windmilling the unneeded oil back into the pan aerates the oil and raises its temperature. A higher oil temperature can also affect the engine by raising the water temperature.

[Comment #5: This statement also applies to excessive volume as well.]

He said that although each engine might be different, the relief valve would probably start to open around the oil volume that could be used at 3,500 engine rpm. So, consider that too much oil pressure wastes horsepower.

[Comment #6: Having met the pressure requirement, means the volume requirement has been met as well. If volume requirementis not met, pressure would not build to that set by relief valve. See post from the 'dude', along my previous post.]

"The stock pump can take care of the bearings on most stock or near-stock engines. There are two good instances where a high-volume pump should be used. In a case where the bearing clearances have been opened up, allowing more oil to flow through, the higher-volume [pump] would be a benefit. This situation is not as prevalent now as in the past. Most engine builders seem to tighten up the bearing clearances now.

[Comment #7: See comment #4 under 'Stock Oil Flow'.]

"The other situation is when an oil cooler, or some other restriction, is added to the oil system. Then, additional flow is needed."

[Comment #8: "or other restriction"...Correct me if I am wrong here. Since when will volume correct a restriction? I am in the camp that reasons, a restriction calls for more pressure to overcome. Bearing clearances, a form of restriction, allow pressure to build. AFAIK, more volume is of little value in overcoming a restriction. Bearing clearances need to be increased, before more volume can be used effectively. Without supply changes (pressure or volume), increased clearances will cause pressure to drop.]

The high-volume pump can refill the accumulator faster while still having enough capacity to supply oil to the engine. In case you
haven't heard me say it before, I think an oil accumulator should always be used on a circle track race engine with a stock pan.

[Comment #9: Faster, yes. The oem sbc pump is capable of
delivering 9 gpm. How much time is needed to deplete/refill the
reservoir? Remember, it was stated, excessive pressure is not
required at high rpm. At what point, is the accumulator a band-aid, for a situation that calls for a system superior to 'stock', or
even a dry sump system?]

Under Heading: Use A Big-Block Pump?

Osterhaus and I had spoken before about the use of a big-block
Chevy oil pump on a small-block engine. My long-held opinion was that the big-block pump was costly overkill. I had thought it pumped too much oil, therefore heating up the oil, and was thus unnecessary on a stock-type engine.

[Comment #10: I don't recall a relevant rebuttal from either engineer!!]

Under Heading: Stock Conclusions

Use a high-volume pump when an oil cooler or an oil accumulator are plumbed into the oil system. High-pressure pumps can overwork the oil and cost power. The Chevy big-block pump may be a good alternative.

[Comment #11: First sentence; don't know 'bout you, but I'm not convinced. Second sentence; see comment #5 above. Third sentence; this article presented no evidence/proof to support such a claim. In fact, no relevant support info was even addressed.]

Originally posted by Zero_to_69
Once the engine is warm, the pressure "LIMITS" to 40 PSI at 3500 RPM. As the motor raises above 3500 RPM, the pressure drops to about 30 PSI and climbs back to 40 PSI...it never exceeds 40 PSI.

That dip/drop in pressure is a warning sign. Depending on how responsive your gauge is, it could conceivably be dropping lower than it is registering. You could very well be cavitating/sucking air. The question is why?

That was the first thing I checked - oil level. It's reading proper on
the stick.

Failing that, I tried a new oil filter. Same issue.

A little more history: My previous motor had what I believed to be
a stock oil pump and pressure regulation.

Hot values were 20 PSI @ ~900 RPM, and up to 60 PSI @ 6000 RPM.

I thought this was the norm and grew accustomed to it.

When I dropped in my new motor, I picked up a new pump and
it had the pink spring for high pressure operation. Not my liking,
hence the installation of the black spring.

I was told the black spring was stock regulation? I was also told
the white would give me stock regulation? Hmmmm...

Not sure what's going on. I don't believe it's a bad pump because
it threw out 60 PSI with a pink spring, and afterall it's "new".

Now I'm a little uncertain as to what I should keep. To be honest,
I think the drop in pressure is a little strange while rev'ing over
3500. I would expect the gauge to hold steady rather than drop
and climb again.

I've used the same oil grade/brand, same oil pan, etc. and never
experienced issues with cavitating, or sucking air.

Lastly, the bearings were plasti-gauge to 0.0015"

Photo link:
http://members.rogers.com/tdese739/plast.jpg

Arnie,
Don't know what the problem is about a HV pump.I can tell you that in my dirt track sprint car from the late '60's to early '70 we used the GM BB pump.My engine had .003 on the main's and .0025 on the rods.We ran Kendal GT-1 50W not for the clearances but when the radiator got packed up,water temp went over 300* and the oil was like water and you still had 15 laps to go(didn't know what syn. oil was)I ran the same block,crank,rod's and piston's for three years@5 nights a week in Penn.It wasn't robing us of enough power to worry about and the engine ran all season without a teardown.When I got time I would look at the plugs and lash.So to me the questions about a HV pump are a non factor.If you go screwing around with the relief spring you SURELY CAN have to much pressure and cut a nice groove all the way around the brg.(not good)If you want to experiment, put it in a bucket of oil and ger a BIG drill make a guage adaptor and see what it does.But those engineers pretty much know what it takes to get the job done.
The reason for the small clearances on todays engines is from the modern day THIN oil,and service LIMITS on an LT-1 are from .0007 to .0030 on the main's.So LIMITS are not any different than in the '60's

Just wanted to see you write all that Arnie. :lol:

I don't agree with everything written there either but I don't agree with alot of stuff out there these days.

Anti-cavitation features and blueprinting are more important to me than volume/pressure etc.. So I like to use pumps built with those things in mind in lieu of modifying stock pumps.

-Mindgame

Originally posted by Mindgame
Just wanted to see you write all that Arnie. :lol:


After finished typing it, that is kinda what I felt like, too. :( :rolleyes: :)