Oil pressure, how much is too much

[dan juhasz]

So I just finished installing a mechanical water temp and oil pressure gauge. In a 67 street Hemi, stock trim. I was surprised that on a cold start high idle (1500 rpm) it reads 90 psi. Once warm choke off 700 rpm it drops to 40 psi. Off idle driving 75/80 psi . I wasn’t expecting these numbers. Engine was rebuilt over a decade ago, I don’t have specifics of the build. Is it ok or should I install a different pressure relief spring?
Thanks

 

[R413]

I don’t like it that high. Its not that necessary. Takes lots of power to turn the pump, which can break off the drive end of the shaft or wear out the gear.

and what is pressure it is resistance to flow. So more pressure is more resistance and less flow. Now more flow cools better. So thinner oil gets us there.

ready for the red X from the fans of hi volume pumps and 20/50.

 

[RemCharger]

Those #s are fine.
Last thing you want to do is attempt to lower the pressure in your Hemi.
Unless you have unlimited access to cash.

 

[dvw]

Run it. It'll be fine. If you are running above 30w you can swap it down to 5w30. That will bring it down. I run similar oil pressure with my racecar. It only runs 5w25
Doug

 

[dan juhasz]

I use valvoline VR1 (20w50), if the numbers are good ,I will leave things be, thanks

 

[gtx6970]

Mine is very similar. And I run straight 30wt
Been like that for 20 years

 

[dadsbee]

Where mine runs idling as it warms up and pops the stat and running hot at RPM. 10W40 Penn. Note temp basically hasn't changed!

 

[TrackPack]

At 90 psi the oil filter is the weak link.

 

[Bee1971]

"Engine was rebuilt over a decade ago"

Why worry now
I would say he is good

 

[Geoff 2]

At 90 psi, the hex on the intermediate shaft is greatly loaded....& unnecessarily so.

The conventional wisdom is 10 psi [ hot ] per 1000 rpm. Many engines today are running lower oil pressure to reduce hp loss & load on the pump drive.

I would change the spring....

 

[kiwigtx]

So I just finished installing a mechanical water temp and oil pressure gauge. In a 67 street Hemi, stock trim. I was surprised that on a cold start high idle (1500 rpm) it reads 90 psi. Once warm choke off 700 rpm it drops to 40 psi. Off idle driving 75/80 psi . I wasn’t expecting these numbers. Engine was rebuilt over a decade ago, I don’t have specifics of the build. Is it ok or should I install a different pressure relief spring?
Thanks

Sounds like you have a High Pressure pump, rather than a High Volume pump installed.

 

[lewtot184]

too high for me. high pressure eats up the intermediate shaft bushing and as mention can have an adverse effect on the intermediate shaft hex. this is typical of the high volume oil pumps. simply change the pressure relief spring in the pump.

 

[Darter6]

I don’t like it that high.

My 472 Hemi was the same 90+ cold, 50-60 hot idle and 80 with rpm.
I dropped the pressure to 30-40 hot idle and 60+ running rpm. This was a street car that never saw high rpm.
Just my preference.

 

[JG71B]

I have an all stock '77 400 4bbl out of a land yacht with the factory pump that reads 80lbs cold 40-50 hot and same as yours cruising

 

[OKDart]

too high for me. high pressure eats up the intermediate shaft bushing and as mention can have an adverse effect on the intermediate shaft hex. this is typical of the high volume oil pumps. simply change the pressure relief spring in the pump.

Hmm, years ago I had an engine with a worn out bushing. It did have a high volume high pressure pump. Back then I just chalked it up to being improperly burnished, never thought the pump could’ve caused it.
All other engines, I’ve used high volume standard pressure.

 

[RJRENTON]

So I just finished installing a mechanical water temp and oil pressure gauge. In a 67 street Hemi, stock trim. I was surprised that on a cold start high idle (1500 rpm) it reads 90 psi. Once warm choke off 700 rpm it drops to 40 psi. Off idle driving 75/80 psi . I wasn’t expecting these numbers. Engine was rebuilt over a decade ago, I don’t have specifics of the build. Is it ok or should I install a different pressure relief spring?
Thanks

This is similar to what I get on my 440 six barrel. Its been this way for approximately 25 years. The old adage is applicable: oil pressure is inexpensive insurance against bearing failure. After all, the crankshaft and rod bearings are "floating" on the hydrodynamic wedge of oil generated between the bearing and the crankshaft and respective journal. The oil also cools the bearing interface.....especially furing high RPM and high loads.....like competition or vigorous street contests. I use Mobil One 10W-30 + one pint of ZDDP and a HIGH VOLUME PUMP. Just my opinion of course.....
BOB RENTON

 

[AR67GTX]

Same here on my Hemi except at hot idle it falls to around 25 psi with 15W-40.

 

[lewtot184]

high oil pressure is not an indicator of flow. it's the opposite. high oil pressure is an indicator of resistance to flow.

 

[dvw]

I've experimented with oil pressure in my 580" (4.5" stroke) race motor. The bearings looked fine at 65psi hot. Below that number they did not. Since replacing the lifter bushings it's run 80psi (150 passes). There was zero decline in performance. It has been running the same distributor shaft (bronze gear) and shaft bushing for 10 years at over 900 passes. The rpm limiter is set at 7400 rpm. as stated 5w25 JR1 synthetic oil.
Doug

 

[padam]

I've experimented with oil pressure in my 580" (4.5" stroke) race motor. The bearings looked fine at 65psi hot. Below that number they did not. Since replacing the lifter bushings it's run 80psi (150 passes). There was zero decline in performance. It has been running the same distributor shaft (bronze gear) and shaft bushing for 10 years at over 900 passes. The rpm limiter is set at 7400 rpm. as stated 5w25 JR1 synthetic oil.
Doug

Pastor Doug preaches the truth.