High Pressure Oil Pump Decisions...

[Gerald Morris]

Good Sunday Morn C-body Moparians!

Took the family to Phoenix and back yesterday for the Babushka's birthday, with Gertrude cruising effortlessly along I-10 at average speed ~85 mph. This engine has never run better for us in the near 10 years we've used it. I attribute some of this good performance to the 440 Source adjustable pressure relief valve cap and screw combo I installed on the standard Melling M63 pump this past spring, giving us a highway oil pressure averaging 60 psi. Alas! Higher oil pressure can also LEAK more readily, and that damned cap spews oil into the driver's side compartment on my nice new suspension rubber! NOT acceptable! I had to replace about 6 oz of oil for the 224 mile run, most of that having been lost through that adjustable cap.

So, WTFITBD? I have an embarrassing number of oil pumps, including one Melling 63HP of unknown condition. I suspect any other oil pump I own will require new O-rings and a gasket, though the rotors, relief valve plungers and springs likely are fine for MOST of these.

So, should I just bust a #20 and get a new high pressure spring, and O-rings, and cap that M63 with a standard cap? I think this will prove the surest way to eliminating the spew. I want to keep the oil pressure around 60 psi when running the engine over 3000 rpm, and see no other new leaks around the engine to worry me for now. Aside from the high pressure spring, do ANY of these HP pumps have any differences from the standard ones? I've not seen such, but admit this makes no basis for a conclusion by itself.

 

[CBODY67]

Not understanding the "spewing" mentioned and how it relates to the oil pump.


CBODY67

 

[413]

You don't need a high pressure oil pump. And the 60 psi oil pressure didn't make the engine run better on your road trip, that was your attention to the tune and timing. Along with a good tank of gas instead of some old junk gas from a discount station.

The oil on the bushings needs to stop right away as you know.

More pressure is more work for the pump and more drag. If you go by the wives tale 10 psi per 1000 RPM then you need 30 psi on the Highway.

I use stock pumps on stock-ish engines and get from 45-50 on the freeway when hot. It all depends on bearing clearances and weight of oil.

You can shim the spring with a thin washer to taylor the pressure where you like it.

 

[Gerald Morris]

You don't need a high pressure oil pump. And the 60 psi oil pressure didn't make the engine run better on your road trip, that was your attention to the tune and timing. Along with a good tank of gas instead of some old junk gas from a discount station.

The oil on the bushings needs to stop right away as you know.

More pressure is more work for the pump and more drag. If you go by the wives tale 10 psi per 1000 RPM then you need 30 psi on the Highway.

I use stock pumps on stock-ish engines and get from 45-50 on the freeway when hot. It all depends on bearing clearances and weight of oil.

You can shim the spring with a thin washer to taylor the pressure where you like it.

This has occurred to me. Now with the timing and ignition nicely tuned, I'll listen carefully to that engine at a lower oil pressure. I DON'T like to use power to turn that oil pump against a high load. Yes, I don't care to change out my new rubber anytime soon, so I might drop the pressure back down permanently, if I hear no evil sound from the lower part of the engine.

I run Chevron 91 octane gas. They're the only vendor down here worth buying from. The rest sell moonshine, summer and winter.

 

[Gerald Morris]

Not understanding the "spewing" mentioned and how it relates to the oil pump.


CBODY67

Leaking at the gasket and the pressure relief cap.

 

[Gerald Morris]

A coda...

Changed the oil and reverted my oil pump to the stock Melling pressure relief valve cap, shimmed with a couple 1/4-20 lock washers in the cap, which gives me oil pressure ~55 psi @ 3k rpm, 180 F temperature running my winter weight 10W 30 oil. I saw when removing the pump to twiddle it that my previous installation resulted in a tear in the pump to block gasket, making the second leak, in addition to the more visible but less destructive leak around the 440 Source cap, and the most destructive leak in the WIX oil filter gasket. I wiped off the more readily removable oil from the surfaces around the pump, to more readily discern if any further leaks occur. Such doesn't appear to be so. Now, I must replace a sway bar link bushing and the lower radiator hose. The bushing was BADLY eroded by the oil shower. I saw no sign of it getting to the LCA bushing, for which I thank St. Joe and his Boss both....

For future reference: Those paper oil pump to block gaskets are best stuck down to the oil pump before attempting to guide it around the transmission cooler lines, then back onto the driver shaft from the cam/distributor shaft, then tightening it onto the block. That torn gasket was NOT my first, alas, but WILL be my LAST! I dabbed some Indian Head shellac onto the pump surface, stuck the gasket exactly in position and gave the shellac a half hour to firm up enough to retain it, then bolted the pump onto the block sans difficulty. I chose the venerable shellac over some carb gasket "tackifier" also from Permatex which I keep handy purely for cost effect. (I've used Indian head on the 2-bbl carb gaskets with good result in the past too.) This time, not even the WIX oil filter gasket leaks. I still will lose a little oil out the #1 & 3 cylinders, but that's about it for oil loss now.

 

[furious70]

Relevant perhaps, the HV pumps have a longer body for the bigger rotors, are all hp pumps built with those bigger rotors?
A HV pump will aid weak hot idle psi without pumping up drive rpm psi.

 

[CBODY67]

(High Volume pump, Standard Pressure)

 

[Gerald Morris]

Relevant perhaps, the HV pumps have a longer body for the bigger rotors, are all hp pumps built with those bigger rotors?
A HV pump will aid weak hot idle psi without pumping up drive rpm psi.

I'm familiar w the HV pumps. The HV rotors are taller, for the added volume, otherwise identical. In Gertrude's case, BAD idea. HV pumps drain the sump quickly, and with a standard 4 qt sump, I DARE NOT risk such interruptions.

Idle in gear pressure now ranges from ~11 psi when 190F to 20 psi at 160 F, 600 rpm. Warm max pressure, for w >= 3500 rpm ~55 psi. At 160 F, the same w = 58-60 psi. That's plenty of pressure, and I hear no lifter clatter or rod knocking warm or cold. I should obtain some milder vacuum advance pots than the 12.5 degree ones I've been rebuilding my distributors with, as those push the timing up a few degrees beyond optimum. I think I have ONE 9.5 degree vac pot, which I'll install to the current distributor, which otherwise, sans vac advance, is running the engine fairly well. The mech advance cam is 11.5 degrees, which, I think, is fairly common for mid 1960s car distributors. I prefer to limit the vacuum, as I like mech advance, especially for WOT conditions when the engine is accelerating up from traffic light idle through the low thousand rpms range.

These sundry little adjustments can be tried around Yuletide, AFTER I get brakes, suspension, cooling and tires all up to my specs.

 

[413]

Relevant perhaps, the HV pumps have a longer body for the bigger rotors, are all hp pumps built with those bigger rotors?
A HV pump will aid weak hot idle psi without pumping up drive rpm psi.

This information is contradictory to my experiences with the thick oil pumps. They have high pressure at all times. Idle and revved up.

I see no option to buy high volume standard pressure pump. They just label them high volume.

 

[Gerald Morris]

This information is contradictory to my experiences with the thick oil pumps. They have high pressure at all times. Idle and revved up.

I see no option to buy high volume standard pressure pump. They just label them high volume.

Well, if one increases the volume of a fluid flowing through the same sized aperture, the pressure MUST increase.

 

[plymouthguy1960]

You don't need a high pressure oil pump. And the 60 psi oil pressure didn't make the engine run better on your road trip, that was your attention to the tune and timing. Along with a good tank of gas instead of some old junk gas from a discount station.

The oil on the bushings needs to stop right away as you know.

More pressure is more work for the pump and more drag. If you go by the wives tale 10 psi per 1000 RPM then you need 30 psi on the Highway.

I use stock pumps on stock-ish engines and get from 45-50 on the freeway when hot. It all depends on bearing clearances and weight of oil.

You can shim the spring with a thin washer to taylor the pressure where you like it.

That's how we used to do it back in the day. We'd just remove the cap from the spring chamber and add a washer or two to get he pressure where we wanted it on the gauge.

 

[furious70]

Well, if one increases the volume of a fluid flowing through the same sized aperture, the pressure MUST increase.

Yes, but the pressure relief system must be considered. At hot idle the HV pump isn't going to make enough psi to be on the bypass but it will make more psi than the standard rotor pump because of this principle. At higher rpm, more psi, and pressure the bypass will come into play.

 

[Gerald Morris]

Yes, but the pressure relief system must be considered. At hot idle the HV pump isn't going to make enough psi to be on the bypass but it will make more psi than the standard rotor pump because of this principle. At higher rpm, more psi, and pressure the bypass will come into play.

All true enough up to a point, that being which the pressure relief valve has fully compressed the piston in the relief cylinder. Increased volume through the galleys, bearings et al beyond that point will increase pressure. Mind, the increased volumetric capacity of the HV pumps isn't so great as to blow gaskets, usually, and with the right spring in the relief valve, things will level out.

 

[furious70]

Just another tool in the toolbox, the HV pump will give more hot idle psi without having to stack washers in the spring that will affect the psi at other rpm. A person may or may not want that (nobody needs 80psi going down the road)