How much oil pressure is to much for a stock 350

[1977C20Silverado]

I got a stock 350 4 barrel that I just replaced the oil pump on, and I haven’t had it idle for more than 5 minutes at a time, mainly cause I’m working on it in the middle of the night. But whenever it is idling it starts up great, then goes up to 55-60 psi. And if you rev it it goes past 60. Considering the gauge only goes to 60, how much oil pressure is to much? Before the old pump went out, it idled around 30. It’s a standard melling oil pump, not high pressure, so it’s a little confusing. Just the break in period? Idk thanks

 

[MarineOne]

Possible you got a high volume pump?

 

[Shorty81]

Factory gauges are notoriously inaccurate. My high volume Melling cold idles at 65 lbs on a mechanical gauge. You should be ok.

 

[PrairieDrifter]

You'll be good, mine runs about 60 at higher rpm. then idles around 30-40 depending on temp.

A mechanical gauge really opened my eyes to operating temps, that being load, actual temperature outside, engine temp relative to outside temp, rpm, engine temp after extended driving and oil temp. The electronic gauges arent fast or really accurate. Sometimes not fast enough to even catch some fluctuations.

Enough rambling. My Melling pump runs about the same on an average cold start. Higher when it's colder. You're all good, as long as your seals are decent.

 

[GTX63]

If you have the original set up in your 1977, your oil pressure gauge is mechanical, with a copper capillary tube running from the motor to the dash.
If it is newer, it bases the pressure on the resistance of the sending unit, and runs thru contacts and circuit board, son it might be off a bit. Someone I know who worked for GM back in those days said they accepted 5-10% variation as acceptable.
My 44 year old 350 daily driver and unknown mileage reads about 55-60 cold and 30-35 hot. That is the factory gauge and pump. I know those readings are close because it previously had an aftermarket gauge and I also confirmed with a mechanical test.

 

[GTX63]

As for is it too high? I am aware of street/strip set up running 80 psi+.

 

[ChuckN]

Thinking of this from the other side, what would happen if the oil pressure was actually too high so as to cause a problem- what’s the first thing that would give? That’s not necessarily a rhetorical question.

I would think it would be hardest on the oil pump drive itself. Seals…rear main, oil filter gasket? Can’t remember if the rear main is just a seal or if it sees oil pressure against it.

If you want an actual reading, you could get an actual gauge to check. My instinct is that in the 80s would be ok but if you test with a gauge and it does something north of 100 it would be worth looking into. Just my measly $.02.

 

[squaredeal91]

Sounds like high volume pump. All my small blocks always get one because I believe there a good upgrade. Your description sounds like normal behavior with a cold engine.

 

[Ricko1966]

Thinking of this from the other side, what would happen if the oil pressure was actually too high so as to cause a problem- what’s the first thing that would give? That’s not necessarily a rhetorical question.

I would think it would be hardest on the oil pump drive itself. Seals…rear main, oil filter gasket? Can’t remember if the rear main is just a seal or if it sees oil pressure against it.

If you want an actual reading, you could get an actual gauge to check. My instinct is that in the 80s would be ok but if you test with a gauge and it does something north of 100 it would be worth looking into. Just my measly $.02.

What happens with too high,is bearing erosion. Kinda like how water carved out the grand cannon. Rule of thumb is 10psi per 1000 rpm

 

[ChuckN]

What happens with too high,is bearing erosion. Kinda like how water carved out the grand cannon. Rule of thumb is 10psi per 1000 rpm

And there ya go. Thanks!

 

[Memaloose]

All the small blocks I've ever owned averaged 15-40 PSI at cold idle. Depends on season and type oil as well from my experience.
283, 327, 350 and 400.

 

[Buck69]

Why did you replace the original pump? There is no gain to having higher than recommended oil pressures. Only draw backs. The 10 psi/1000 rpm is a minimal rule of thumb. Check your pressure with a mechanical gauge (at operating temp) to see if there even is a problem.
Oil viscosity will also greatly effect your reading at lower temps, if you happened to have tried something different.

 

[mtbadbob]

My stock 350 TBI runs about 60 on the factory gauge at highway speeds. It'll idle down to about 35, and I've changed the gauge once, a new sending unit & new connection at the sender. I also cleaned the contacts to the cluster really well when I had it apart a year or so ago. I've yet to check with a manual gauge, but I figured as long as it's full of oil & the gauge is moving, it should be fine.

 

[sidschev]

any thing over 60 is way too much from the top of the engine. they dont really need that much pressure ..whats important is it has oil flowing through them bearings.. i had an international that had zero oil psi and it ran fine . dang thing never had oil presure , but the oil flowed through it kinda sloooow......

 

[Ricko1966]

The way I have explained oil pressure,the dirt simple explanation. Think of an air hockey table, the puck floats on a cushion of air,it never touches the table. Same with your bearings,your crank,rods,and cam are floating in pressurized oil. Your bearings don't touch the crank or cam. Turn off the air the puck skids across the table,same with not enough oil pressure. Not enough and the bearings skid on the journals andcwipe out the bearings,more pressure doesn't make it better, enough to make it float is all you need. Now here's where it gets interesting you cranked the timing up,and leaned out the mixture,that detonation,you just created,the sudden pressure spikes can over power that oil cushion and hammer out your rod bearings. Biggest rod bearing failures,oil starvation and detonation.