Another oil pressure discussion

[Car #4]

I was reading the oil pressure thread by ZDECKICH and it got me thinking about my own situation. I have a 440 that rarely gets above 22 psi even when over 3000 rpm. This is on a OEM brand repo gauge, I will hook up a mechanical gauge to see what it says. I was talking about it with a friend and he asked what oil I’m using. I said 10 W30. He suggested going to 20W50.
Now here’s my thinking. 20W50 should give a higher pressure reading because it’s a thicker oil and so it’s harder to push through the slim tolerances of the engine. But…is it really doing more lubricating? Are we moving as much oil? Or, because it’s harder to move are we actually pushing less oil volume throughout the engine?
Let’s stretch that out a little on each end and compare a 5 weigh synthetic to a 90 weight gear oil. We all know we’ll move a lot more volume of the synthetic than we will the gear oil. So by the same token, would we not move more 10W30 than we would 20W50? Which would do more lubricating? Or am I missing something in the science here? Maybe we shouldn’t worry so much about the actual oil pressure reading, as long the gauge isn’t sitting at 5 when we’re at highway speed.
These are just the theoretical thoughts of my small mind. I invite your input.

 

[hunt2elk]

High volume or standard pump? I couldn't live with 22psi at 3000, that is the absolute minimum at hot idle for me.

 

[ruffcut]

I'm thinking if those #'s are correct, it's time to tear that mother down for a rebuild before it seizes up or throws a rod.

 

[rickseeman]

Let's not try to overthink this. You have 22 psi driving down the highway at 3000 rpms. I say you have low oil pressure and should do something about it. Normally I would say put in 50w and see what happens but it's September and you are in Canada so I'm not liking that idea right now. I would put a high volume oil pump on it because I can't think of anything else that has a chance of getting me where I want to be. And yes I think you should worry about the actual oil pressure reading. And since you asked for opinions, I doubt I would run 10-30w in any 50 year old muscle car engine. It's not a Honda Civic.

 

[MWbirdLOVER70]

10 lbs per 1000 rpm

 

[Darter6]

I doubt I would run 10-30w in any 50 year old muscle car engine.

Agreed. My old truck,a 85 318 was used when I put it in and had unknown miles.I use it as a truck.
I agree and use 20-50 during the hot summers here. Factory gauge and also A pressure light.
So far still kicking after 10+ years. When you put a good mechanical gauge in you may see better results.

You have 22 psi driving down the highway at 3000 rpms.

Along with the others you may be headed for a rebuild.

 

[lewtot184]

Do the reliable mechanical gauge first. Maybe you have a problem, maybe not.

 

[Runcharger]

Try a good, known manual gauge. Then it's tear down the engine before you really hurt it and it costs a lot more money to repair.

 

[#41]

I'd throw 10/40 in it like recommended. I doubt you are driving it in the winter? Then, if more is needed, because I'm a cheapskate, I'd shim the oil pump spring and forget about it.

 

[4mulas]

At 20 psi over 3k rpm is not good.

Things likely have big clearances likely from wear you’ll have the car off the road at the end of this month or so, I’d plan on a refresh if I were you.

Thicker viscosity may coat better.

Idling hot in my motor is around 30 psi, then at anything above 1700-1900 rpm I’m at 70. 22psi would not make me feel good about going anywhere outside of normal tow truck services.

 

[lewtot184]

If this is a stock high mileage engine the oil pickup could be full of broken valve seal stuff.

 

[GTXDAN]

I had a friend who bought a Ferd pickup back in the 80s that looked like new but had a "new" engine installed. It didn't use oil but had same issue, low oil pressure. I pulled the pan and found the bearings were shot. Crank was fine so I threw new rods and mains in it and a new pump and he drove it for years. A new pump might be a waste of money if it's worn out. I'd pull the pump apart and see what it looks like, and if it's okay you're going to have to open it up and look at the bottom end.

 

[Don67Satellite]

I ran Royal Purple 10-40 for awhile in my 440, gave me about 35-40 at idle, 50 at cruising speed.

I currently run Valvoline VR1 20-50, and my pressures are about the same.

 

[lewtot184]

There's recommendations of heavier oil, big pumps, and I wouldn't do any of that. 10w30 " might" be a little light on a worn engine but not a deal breaker. I have a stock 440 with a stock pump with red spring, stock bearings and clearances, stock valve train and all. I've done 10w30, straight 30, 15w40w and there's little to no difference in pressure. Stock main bearings are half groove with around .0025" clearance. Pressure is always stable, just like in the 60's when I first starting messing with big blocks.

When the pressures get low then there's usually a fundamental mechanical problem. The first easy check is to take a valve cover and look for black particles from the valve seals. If any are found then dig deeper. If everything is clean and looks good then take off the oil pan and go from there. It's possible for the relief spring in the pump to be stuck and that's a very easy fix.

 

[Car #4]

New Edelbrock heads. I doubt there’s schmutz from valve seals.

 

[PRHeads]

The only fresh BBM build I have any personal experience with that had low oil pressure was a repair job on a 440 that didn’t originally have an oil pressure problem.
One of the items that got replaced during the repair was to swap out the HP pump for a HV pump, due to engine getting upgraded to a HR cam, in anticipation of added leakage by the lifters.
I don’t recall what the hot pressure was on the dyno(maybe like 30-40), but it was lower than expected even considering the HR lifters.
We swapped the spring from the old HP pump into the new HV pump and the problem went away.
The old spring was noticeably stiffer than what was in the new HV pump.

 

[Black_Sheep]

If this is a stock high mileage engine the oil pickup could be full of broken valve seal stuff.

And plastic bits from the timing gear…

 

[jdsgtx]

I was reading the oil pressure thread by ZDECKICH and it got me thinking about my own situation. I have a 440 that rarely gets above 22 psi even when over 3000 rpm. This is on a OEM brand repo gauge, I will hook up a mechanical gauge to see what it says. I was talking about it with a friend and he asked what oil I’m using. I said 10 W30. He suggested going to 20W50.
Now here’s my thinking. 20W50 should give a higher pressure reading because it’s a thicker oil and so it’s harder to push through the slim tolerances of the engine. But…is it really doing more lubricating? Are we moving as much oil? Or, because it’s harder to move are we actually pushing less oil volume throughout the engine?
Let’s stretch that out a little on each end and compare a 5 weigh synthetic to a 90 weight gear oil. We all know we’ll move a lot more volume of the synthetic than we will the gear oil. So by the same token, would we not move more 10W30 than we would 20W50? Which would do more lubricating? Or am I missing something in the science here? Maybe we shouldn’t worry so much about the actual oil pressure reading, as long the gauge isn’t sitting at 5 when we’re at highway speed.
These are just the theoretical thoughts of my small mind. I invite your input.

Your oil pressure is too low! It should be between 40 and 45 psi no matter what oil you use! I personally use the 20/50 Castrol in my 440 that was built in 98 and runs as strong today as the day it was built! Sounds like you have a weak spring in the oil pump

 

[Gary Gaz]

Doesn't FSM say 20W50?
Fresh build 30 over with High volume pump with standard pump spring. 50W60 Penrite zinc oil, about 75-80 cold and about 65 at 60mpg. probably a bit on the high side, but goes ok, cheap after market electric oil pressure garage, so could be that too.
You could get the uprated oil pump spring from places like Mancini racing they also do an adjustable plug as well

 

[Orig69]

So your OEM reproduction oil pressure gauge rarely gets above 22 psi even when it's higher than 3000 rpm

My guess is that repo oil pressure gauge is stuck in the 20s