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Oil pump question

furyus

furyus

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Guys, I have a 505 stroker that is all new. Roller cam, Indy heads.
When my engine gets warm, around 190*, the pressure drops below 20 psi at around 800 rpm. This is the same thing that it did with the old 440. I used this pump because it was new. So, I need an oil pump that has higher output at idle rpms, but not at higher rpms. So my questions are, if I shim the pump, does that raise the idle psi? If not, then I need recommendations for a new pump. I don't want to use a stock style, cast iron pump. I'm looking for something that is maybe billet, but mostly I just need one that puts out more at idle. Thanks
 
A high volume pump will get you a couple more hot idle psi over a standard pump, otherwise you could try thicker oil. I did both those, and then cut 3/4 coil off the stock black spring to get my cruise pressure down to the low/mid 60's.
 
Turn up the idle a little.
 
High volume pump. Motors are too expensive to FAFO experimenting with dangerously low oil pressure for no good reason.
 
For oil pumps,
High Volume = taller gear rotors
High Pressure = stronger relief spring
A relief spring doesn't even come into play until you hit the relief pressure. So at 20 PSI it doesn't matter what spring you have, the pump is putting out max pressure/volume regardless. With taller rotors, the pump is capable of higher volume, which can translate to higher pressure at idle depending on clearances.
In your case, a high volume standard pressure pump is what you want.
FYI, if a high volume pump doesn't make a difference, maybe those hyd rollers are bleeding off too much oil? But with 20 PSI at hot idle it's fine.
 
Last edited:
Shimming will increase the oil pressure. I would try a 1/16" shim, make sure it is hardened [ a s/steel washer would be good ].
 
As above....
High volume standard pressure pump is what you want (more spring/shim will only get you more cruise pressure, won't do a thing at idle)
If that still doesn't get you comfy, bump the idle speed a bit, and run straight heavier weight oil. You probably have some loose clearances somewhere.
And there's nothing wrong with a iron pump (more durable than a aluminum pump) except 2 or 3 more pounds.
 
Geoff 2 said:
Shimming will increase the oil pressure. I would try a 1/16" shim, make sure it is hardened [ a s/steel washer would be good ].
Click to expand...
Shimming the spring will not raise the idle pressures.
 
Pressure readings are resistance to flow. Large internal clearances or oil viscosity is thin enough don't create as much resistance. The pump can't produce enough volume to create high resistance to flow at low rpm. Once pump speed goes up pressure increases as more volume is being moved and pressure increases. Thick oil to increase idle pressure is a band aid. Thick oil reduces flow. Reducing flow doesn't cool bearings as well. Bearing cooling is an important consideration. If pressure is suffcient at working rpm at normal running temps, then the viscosity is fine. A higher volume pump will move more volume increasing idle pressure. The relief spring only comes into play when the pumps volume is great enough that the resistance to flow exceeds the pressure setting of the spring. Then the bypass valve opens limiting pressure. Shimming the spring will increase higher rpm pressure. As for 20 psi at idle? If the pressure is 60 psi or higher at at higher rpm? I'd be fine with it.
Doug
 
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dvw said:
Pressure readings are resistance to flow. Large internal clearances or oil viscosity is thin enough don't create as much resistance. The pump can't produce enough volume to create high resistance to flow at low rpm. Once pump speed goes up pressure increases as more volume is being moved and pressure increases. Thick oil to increase idle pressure is a band aid. Thick oil reduces flow. Reducing flow doesn't cool bearings as well. Bearing cooling is an important consideration. If pressure is suffcient at working rpm at normal running temps, then the viscosity is fine. A higher volume pump will move more volume increasing idle pressure. The relief spring only comes into play when the pumps volume is great enough that the resistance to flow exceeds the pressure setting of the spring. Then the bypass valve opens limiting pressure. Shimming the spring will increase highr rpm pressure. As for 20 psi at idle? If the pressure is 60 psi or higher at at higher rpm? I'd be fine with it.
Doug
Click to expand...
Well said.
 
turbine68rt said:
Do you know what your bearing clearances are, and what type of mains you have? Half or full-groove?
Click to expand...
I don't know what the bearing clearances are. It was a 440 source kit that was built in 2020.the shop that built the short block is gone. I will go to the 440 source website, and see what type of bearings they gave with the kit.
 
dvw said:
Pressure readings are resistance to flow. Large internal clearances or oil viscosity is thin enough don't create as much resistance. The pump can't produce enough volume to create high resistance to flow at low rpm. Once pump speed goes up pressure increases as more volume is being moved and pressure increases. Thick oil to increase idle pressure is a band aid. Thick oil reduces flow. Reducing flow doesn't cool bearings as well. Bearing cooling is an important consideration. If pressure is suffcient at working rpm at normal running temps, then the viscosity is fine. A higher volume pump will move more volume increasing idle pressure. The relief spring only comes into play when the pumps volume is great enough that the resistance to flow exceeds the pressure setting of the spring. Then the bypass valve opens limiting pressure. Shimming the spring will increase highr rpm pressure. As for 20 psi at idle? If the pressure is 60 psi or higher at at higher rpm? I'd be fine with it.
Doug
Click to expand...
Wow, what a great explanation. I already have 20w-50 oil in it. i would be happier if it had another 5 psi. Thanks for taking the time to explain all that.
 
So, my question is still
Are there any pumps that put out better pressure at idle than the generic high volume pump.?
Do hydraulic roller lifters cause lower pressure? (Howard's brand).
 
I have the same low oil pressure issue with my SB stroker. Oil pressure changes with just a thermostat change, 180 vs 195. Have gone from 10-30 to 10-40 and now 20-50. Haven't lost an engine yet with low pressure, been 5 years, rod and mains, rest of engine parts look fine.

10-40 oil/ 195 thermostat/ 15 oil psi at idle
20-50/ 195 thermostat/ 22 psi at idle, was just experimenting with this, may go back to the 10-40.

Lucas Hot Rod with Hot Shot FR3 additive
Maybe a straight weight oil would change things, but I am staying in this window.
 
Bird 426 said:
I have the same low oil pressure issue with my SB stroker. Oil pressure changes with just a thermostat change, 180 vs 195. Have gone from 10-30 to 10-40 and now 20-50. Haven't lost an engine yet with low pressure, been 5 years, rod and mains, rest of engine parts look fine.

10-40 oil/ 195 thermostat/ 15 oil psi at idle
20-50/ 195 thermostat/ 22 psi at idle, was just experimenting with this, may go back to the 10-40.

Lucas Hot Rod with Hot Shot FR3 additive
Maybe a straight weight oil would change things, but I am staying in this window.
Click to expand...
Thanks. This is interesting. I guess I will have to stop worrying about it.
 
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