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TR2/3/3A High Oil pressure

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Simmo

Simmo

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I have had a few TR3a's and they have all behaved the same with oil pressure. i.e. around 70 to 80 psi at normal driving.
I just bought another one which has had a major rebuild some 2,000 miles back.
At start the oil pressure is 100psi which I consider to be too much.
After driving about 5 miles and engine hot it drops to the normal 70-80 psi.
Brand new electric Smiths gauge but also showed the same on the old Jaeger gauge.
20W -50 Penrite, new oil and new filter.
This 100 PSI reading seems wrong. Can anyone offer suggestions?
 
Use thinner oil until it gets broken in better. 10W40 or 15W40.
 
Under what conditions? If you can't make 70-75 psi running at 60 mph with the oil hot, I'd say there is a problem. (Check the gauge first, they often lose accuracy as they age.)

But 50 psi at hot idle would be excellent with that kind of mileage.
 
The oil pressure regulator should maintain the approx. 75 psi through a wide range of oil viscosities and over a long engine life. The 2 exceptions are that oil is too thick at cold start-up for the regulator to reduce the pressure, and once you have a certain amount of excessive wear the pump does not put out enough volume to maintain the 75psi any more.

In short, if your pressure drops below 75 psi in a warm engine at speed, and 20w50 oil and adjusting the regulator pressure will not bring it back up...then it's time to start planning on a rebuild. Not to say the engine won't run many more thousands of miles after being worn out. I had an old Ford pick-up that would only hold 2psi at idle and 25 on the highway...and I drove it 10 years that way.
 
I don't know if or why a TRiumph engine would be an exception, but Smokey Yunick* proclaimed that 10 psi/1000 rpms was all that was needed.
*You might have to 'google'.
 
That's a good rule of thumb, but doesn't always apply. In racing, where every 0.1 hp is important, you don't want to waste any power in developing oil pressure.

Probably is "enough" for the TRactor motor; but the design was created to provide a comfortable margin of safety above that. I'm not saying 50 psi at speed is reason to pull over and call for a flatbed; but it does indicate that something is not "working as designed". Unless of course, you've deliberately modified your engine to run low oil pressure, ala Smokey Yunick.

Besides which, 50 psi IS 10 psi per thousand rpm, at 5000 rpm redline.

Back in high school, I had a summer job hauling fertilizer. One of the trucks we used would turn on the idiot light at cold idle; when it got hot enough the light would be on even driving down the highway. It ran for a long time that way (longer than I had the job), but a friend of mine told me it eventually threw a rod.
 
The correct oil pressure is 40 - 60 lbs/sq" in top gear at speeds 30 - 40 mph. Once the oil is hot use the oil pressure regulator to adjust. From page 48 of the Service Instuction Manual for a TR2.
I was told that high oil pressure can "wash" the bearing face of some types of bearings. FYI the contact bearing face on new Tri-Metal bearings, known as the overlay can be less than .001".
 
Lotta things changed between the time that manual was written, and the TR3A was introduced; including power output and even oil filter type. TR2 and early TR3 used a bypass oil filter rather than full flow as on the later cars.

So anytime the later manuals disagree, I tend to believe them over the workshop manual.
"Practical Hints for the Maintenance of the Triumph T.R.3." says on page 8:
"The gauge should read 70 lb./sq. in. minimum when the car is travelling at normal speeds and the oil is hot."
 
Smokey raced Chevy’s. Triumph raised the TR pressures, obviously for durability reasons.
 
Am I correct to assume that the oil pressure regulator valve only turns down oil pressure and does not raise the oil pressure any? (Unless out of adjustment) So, is the regulator mostly in line to help on cold motors in cool climates, so there is not too much oil pressure on early start ups that could blow out gaskets, or do I have this wrong?
steve
 
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