How important is oil pressure? I have 1980 massey ferguson 265 diesel with no telling how many hours the tach showed about 3000 20 years ago when it quit working. The motor has never been touched and it holds between 50 and 60 pounds of oil pressure at all times. Is that why it is so good?
- Thread starter 1948jr
- Start date
caterpillar guy
Well-known Member
Oil pressure is relative to the make and model engine. My cat truck engines hold around 50-70 PSI and start out at about 80 when started cold. Our 574 usually is in the 30hot and 50-70 cold. It has lots of hours on it from being a loader tractor on a dairy farm in earlier years. It has had a set of bearings rolled through it once 30 or 40 years ago with a set of sleeves and pistons. It had about 5000 hours then and had the water leaking by a sleeve o-ring. Meter last read 7500 20 years ago probably on the 10,0000 -15,000 hour range now. In cold weather allowing engines to warm up makes more difference in engine life than most things will for engine durability I believe.
Dieseltech
Well-known Member
- Location
- Akron, Indiana
Oil FLOW is more important than having high oil pressure. Pressure is caused by RESISTANCE to flow, so an engine with tight bearing clearances and a good oil pump along with a high safety relief valve setting will show high oil pressure. Perkins engines usually carry higher oil pressure than other engines do. One of my Perkins shows 60-70 PSI cold, and holds 60 PSI with engine hot. My White/Oliver forklift 283 diesel shows 40-45 PSI cold, and drops to 15-20 PSI when hot..
It is important that you have oil pressure, but having oil pressure does not mean that there are no problems. Have a tractor that I pulled the pan to replace the rear main seal. While I had it off, I checked a couple of the bearings. !!! @&$?
One of the rod bearings was worn past the copper. So it got a new set of rod and crank bearings. 40 psi oil pressure before, 50 psi after.
One of the rod bearings was worn past the copper. So it got a new set of rod and crank bearings. 40 psi oil pressure before, 50 psi after.
Goose
Well-known Member
The main thing about oil pressure is, it needs to increase along with engine rpm.
On most engines, the oil is fed from the oil pump through the crankshaft to other areas in the engine. As the crankshaft rotates it develops internal centrifugal force that resists the oil coming from the pump. The higher the rpm, the more centrifugal force is generated and the more resistance there is to the oil attempting to enter the crankshaft. The higher the engine rpm, the more oil pressure required to overcome the internal resistance in the crankshaft.
Most old tractor engines seem happy with 20 to 40 pounds of oil pressure because they seldom turn much over 2,000 rpm. The flip side is when I was racing stock cars we used high volume/high pressure oil pumps on SBC racing engines to bump the oil pressure up to around 80 pounds 'cause we routinely turned the engines over 7,000 rpm.
Make sense?
On most engines, the oil is fed from the oil pump through the crankshaft to other areas in the engine. As the crankshaft rotates it develops internal centrifugal force that resists the oil coming from the pump. The higher the rpm, the more centrifugal force is generated and the more resistance there is to the oil attempting to enter the crankshaft. The higher the engine rpm, the more oil pressure required to overcome the internal resistance in the crankshaft.
Most old tractor engines seem happy with 20 to 40 pounds of oil pressure because they seldom turn much over 2,000 rpm. The flip side is when I was racing stock cars we used high volume/high pressure oil pumps on SBC racing engines to bump the oil pressure up to around 80 pounds 'cause we routinely turned the engines over 7,000 rpm.
Make sense?
Hdonly
Member
- Location
- Florida Panhandle
Volume of oil is much more important. Pressure will be different in different engines. My Harley Shovelhead engine runs about 10 psi when hot at idle. Been that way for 25+ years that I've owned it. My Ford 651 tractor ides hot at 45 psi. If the oil pressure is a problem, you will usually hear it.
fixerupper
Well-known Member
High or low oil pressure depends on engine design. There are two ways to get enough oil flow through the bearings. One way is tighter bearing clearances and more oil pressure to push the oil through the bearing. This was the theory Chrysler used in their older V8s that ran 60 to 80 pounds pressure. The other way is looser bearing clearances that dont require as much pressure to flow the oil through the bearing. Older GM engines that ran 30 ish pounds is an example. Then we have the loose old two banger Deeres that ran 15 pounds of pressure at best. I have heard that some racing engines run loose bearing clearances and high oil flow for cooling.
zuhnc
Member
- Location
- Macks Creek, MO
I run 20W50, high zinc, full synthetic AMSOIL in my 1951 8N. 25 PSI hot or cold, summer or winter. zuhnc
Pressures above 5-7 psi provides the engine with sufficient lubrication. Higher pressures within limits is a usual indicator of overall condition of leak points like rod and main bearings, so oil pressure can be used to gauge the condition of the bearings etc. Oil pressure within the system is not the same as oil pressure within the journal. Oil pressure is used to simply supply oil to the journal, the spinning shaft provides for the necessary hydrodynamic lubrication which increases the pressure to approximately 1,000 psi. Think dropping a flat rock into the water versus skipping the same rock across the surface of the water.
My Fords (had a half a dozen of them) run high oil pressure. I understand that different engines (manufacturers) have design engines and some use high volume, low pressure and others the opposite. Case in point was/is my trucks. Chev oil pressure follows RPMs. On used equipment purchases I used to think the engine was worn out till I found out what I said above. RAM runs up to the pressure relief at idle and stays there. Had numerous GMs over the years and 3 RAMs, all acting as described. I remember a JD 3020 I had many years ago and the manual said to set (adjustable on that engine) the oil pressure at 30 psig at some given RPM.
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