Excessive oil pressure

[af2]

No that is why they made a HV oil pump. More volume per revolution
reed

2 more gears is why I use the BB pump.

[Kevin Johnson]

Since oil is essentially incompressible, I believe delivery per revolution depends only on the gear displacement. 'Porting' efforts could reduce internal pressure differentials, cavitation, etc. and possibly slightly lower drive power requirements.

Hi Bill,

Yes, partly. A digression to Yves's threads (he was provided a graph by Melling of a gear pump he was considering)...

Here is a graph from Melling of the output of a gear pump with an orifice (bypass). The flow output of a positive displacement gear pump continues to increase through the fixed orifice and approach a theoretical maximum. At rpm beyond 2000, by decreasing the friction and turbulence on the intake side of the pump, in the then active recirculation circuit of the bypass, the effective available flow is increased over the baseline output. This increase in available flow at a given rpm constitutes an increase in pump volume over the unmodified pump. The red area is strictly hypothetical. If the "port" were to be contoured poorly, available flow could drop beneath the baseline. Beware of backyard porting.

Melling_pump_output_through_fixed_orifice.jpg

Increased_flow_over_baseline_output.gif

[wilson1970]

In response to original post the car has been driven a hundred miles or so. Oil pressure with Valvoline VR1 10w30 has oil pressure at 60-65 when cold. After warmed up and driven hard for awhile pressure is 35 -40 sitting at stoplight. More acceptable.

[racear2865]

No that is why they made a HV oil pump. More volume per revolution
reed

2 more gears is why I use the BB pump.

Sorry you lost me on 2 more gears.
reed

[Kevin Johnson]

The BBC gear pump has additional teeth on each gear. This reduces the pressure fluctuations/spikes. I posted some pics from an SAE paper written by Mercedes in 1975 that show the effect of additional gears on different positive displacement pumps. The paper is: 750051


https://www.sae.org/publications/techni ... nt/750051/

[racear2865]

The BBC gear pump has additional teeth on each gear. This reduces the pressure fluctuations/spikes. I posted some pics from an SAE paper written by Mercedes in 1975 that show the effect of additional gears on different positive displacement pumps. The paper is: 750051


https://www.sae.org/publications/techni ... nt/750051/

Kevin--back in the early days, I ran many BBC oil pumps on our SBC. At that time, it was the thing to do but later found, not so especially with the "stuff" available today. You jst lost me on 2 extra gears. I thought you had a BBC pump with 4 gears. You meant a gear with an extra tooth.
reed

[af2]

No that is why they made a HV oil pump. More volume per revolution
reed

2 more gears is why I use the BB pump.

Sorry I meant 5 more teeth. Than the small block pump.

[GARY C]

The only difference I see is lighting and where QC probably removed unwanted casting. You would have to know what it looked like prior the touching it with a burr to conclude why it was done.

I think you would have to order an HV vs SV to get an idea and probably several brands to further conclude one vs the other.

This is what I think of when someone says modified oi pump.

[Kevin Johnson]

...
I think you would have to order an HV vs SV to get an idea and probably several brands to further conclude one vs the other.
...

Please let us know what you discover in your investigations.

[GARY C]

...
I think you would have to order an HV vs SV to get an idea and probably several brands to further conclude one vs the other.
...

Please let us know what you discover in your investigations.

I don't worry about it, I run a stock BBC oil pump on my race SBC's and a stock volume pump on my street stuff, both still make more pressure than needed. I know CGT, Randy331 spend a lot of time dissecting and modifying pumps to reduce pressure because most out of the box stuff is over kill and hurts power.

One thing I never understood about using a HV pump is that the engine cavities them selves would restrict the volume so it never made since to increase the volume at the pump if you don't have an HV passage to feed. It just increases pressure and robs power or worse, it damages the distributor/cam gear, drive gears of the pump and possibly breaks the housing.

[Kevin Johnson]

Please let us know what you discover in your investigations.

I don't worry about it, I run a stock BBC oil pump on my race SBC's and a stock volume pump on my street stuff, both still make more pressure than needed. I know CGT, Randy331 spend a lot of time dissecting and modifying pumps to reduce pressure because most out of the box stuff is over kill and hurts power. ...

I find it odd that there is such antipathy to the idea that a lubrication engineer at GM could also be a performance enthusiast and recognize the value of a small simple mod. What's up with that MadBill? I did not find that to be the case when I spoke with engineers at Mopar.

...
One thing I never understood about using a HV pump is that the engine cavities them selves would restrict the volume so it never made since to increase the volume at the pump if you don't have an HV passage to feed. It just increases pressure and robs power or worse, it damages the distributor/cam gear, drive gears of the pump and possibly breaks the housing.

Excess capacity helps pulverize free air bubbles to smaller sizes which helps them dissolve into the liquid phase (oil). If you are running lower pressures this is even more important, right? This is straight forward physical chemistry and hydraulic engineering. I think that I have cited the SAE papers that discuss this previously.

I know that I also mentioned that contemporary to the Mercedes paper (750051) was the development of the Porsche V8. By amazing coincidence, the Mercedes V8 was used as the mule motor for the 928. The Porsche engineers published a remarkable history of the development (Project 928 http://jenniskens.livedsl.nl/brochures/ ... 28Book.pdf) I think the Mercedes engineers were well aware of the tribulations experienced at Porsche (their compatriots in Stuttgart ala the big three in Detroit) and were trying to convince them to simply use the motor they started with. I mean, cough, the 924 used an Audi straight four that was also used in a van. It's all good -- it's all German, richtig?

If you take the time to actually read it and carefully examine the photographs you can see that the HUGE VOLUME oil pump was being over-driven and pressure relieved at ~ 5bar (~70psi at 5,000 rpm). Then if you examine longitudinal examples of the production engines (longitudinal in this sense means over time) you will see further great efforts to control aeration. I feel pretty certain that the German engineers did not sleep through their chemistry and hydraulics classes at university.

[CGT]

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New 93442037 purchased today. No super secret cnc deburring on this one. So i guess its just standard volume. I may hit it that area with a flat file and convert it to high volume in the future.

[Kevin Johnson]

...
New 93442037 purchased today. No super secret cnc deburring on this one. So i guess its just standard volume. I may hit it that area with a flat file and convert it to high volume in the future.

Okay, thank you for taking the time to check that specifically.

I did call Melling just now and the technical rep there said that he was unaware of any special milling operation but he did say they checked the pumps for flow. He was skeptical that GM would have this type of "porting" done.

The technical rep at GM Powertrain Performance said he did not have any way to speak with the engineer or team that specced the pump.

It could be that parts are scanned and those that meet the flow design spec are approved and those that do not are milled (??). That could mean that GM is looking at a normal distribution curve for casting flow and specified that only pumps that are one or two standard deviations above the mean are used for performance engines and the balance, including those that fall below the mean are used as standard volume pumps. Again, I am trying to use the principle of charity in interpreting information in the best possible light so as to conform to published "high volume" claims.

[swampbuggy]

CGT, I believe you should opt. For a piece of thick glass w/sandpaper secured to it....over a file.