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Triumph TR6 - Oil pressure relief valve
|Has anyone done a replacement on their oil pressure relief valve; that big hex nut on the block under the distributor? If so, was there an appreciable improvement in oil pressure? Right now I idle hot at about 20-25 lbs.; a little low I think. Solid 50-55 at 3000 RPM.|
|Keith, I am now on my 13th and 14th TR6, both 76 models. My grandfather, a mechanic all his life always told me not to fix it if it ain't broke. Every 6 i've had is as exactly as you describe includeing the two I own now. Get a dial indicator and check the wear on your thrust bearing but other than that don't worry. As a side note, have you ever seen a oil pressure gauge on a Honda that reads anything besides low/high? It is because they run new with less than 10lbs. 4-5 with wear on the engine. It is all about volume with the Japanese because pressure robs hp.|
|I agree. Those are about the exact pressures at the same conditions for mine. Don't worry about it.|
|Ditto from me for my TR3A. When I did my total body-off restoration from 1987 to 1990, I re-did the engine too. When I put it all back together again, I found that the oil pressure was about 90 psi cold and about 75 psi hot. I backed the adjusting valve back down to where it is today. The higher valve setting will give you a higher reading, but it's all back-pressure and will reduce the volume of oil flow. Also if the pressure valve is set too high, the pump will compress the oil more and this will heat up the oil which we don't want and don't need. I'd rather have a greater volume of cool oil flowing at an acceptable pressure than a reading on the gauge that "looks better". I agree with the grandfather from South Carolina.|
BTW, I've driven my TR over 70,000 miles since 1990 with these settings. I use Castrol 20W50 (non-synthetic) oil all summer in my engine and get about 1,000 miles to the quart of oil. I change it and the filter at the beginning of every season (soon for me, now that most of the snow is melting away) and then every 3,000 miles.
Don Elliott, Original Owner, 1958 TR3A
|Don--Exactly how does one adjust the pressure relief valve? I'm one of those high pressure is better folks and you've got me wondering if that's not good.|
|Rick - on a TR6 you'd have to shorten the existing spring, replace it with a "weaker" one, or put a spacer on the nut to reduce the amount the spring is compressed. I wouldn't recommend doing any of those. |
You shouldn't have a problem unless someone stretched the existing spring for some reason - in which case you simply replace it.
|Thanks Brent. So it's your opinion not to mess with the OEM setup? I'm 6K miles out of a compete rebuild and have always seen 90+/70 psi cold/hot idle and in between on the road (20W-50 with 1 qt Lucas stabilizer). Leave it alone?|
|From the details in the reply from Brent above, it appears to me that the TR6 is quite different than my TR3A. On my TR3A, I don't have a spin-on filter assembly. Mine is the original one and there is a large hex locking or jam nut on the side of the original aluminium oil filter housing which is found bolted to the block down below the distributor on the left side of the engine. By backing off the hex nut, I can adjust the oil pressure setting with a screwdriver in a slotted head threaded rod-like piece which is sticking out and which holds the internal spring loaded ball valve. On the TR3A, this assembly is called the "relief valve setting".|
Don elliott, 1958 TR3A
|Rick - that pressure seems awfully high - even for 20W-50! Did the oil pressure RV spring & piston get changed out during the rebuild? You might want to make your next qt. of oil 10W-30. |
Do you use the stock oil filter or a spin-on? there are some spin-on's that are undersized and create alot of backpressure. There's an article in buckeye or VTR about that.
You don't want so pressure so high that the RV is relieving all the time - that's oil that should be going to your bearings.
|Brent--I have the Mocal spin-on with oil cooler option and use Purolator PureOne filters. Also have the external rocker feed. Maybe I'll forgo the Lucas stabilizer at next oil change. I don't know what was done with the relief valve during rebuild. Since my pressure seems high, is there a different spring I can install in the valve body to drop the psi?|
So what are the "correct" pressures anyway?
|Surely the Pressure Relief Valve is to send oil every where that needs it and relieve OVERpressure?? That is how I've always understood it - thus , if pressure is high, everything is getting lubed BEFORE the relief valve opens. Correct me if I'm wrong on this. I'm 90 on startup, drops to 75 hot, w/ 45 at idle - makes ME happy anyway.Peter|
I agree with Peter. The valve is not for adjusting oil pressure, but to prevent excess strain on the oil pump and filter when the car/oil is cold and stiff.
The above point on Japanese cars, that it's volume not pressure that matters, is so right.
Although measuring your blood flow is a better gauge of health but doing do is invasive and dangerous, so the doctor measures your blood pressure. S/he gets alarmed at high blood pressure because we have no blood pressure relief valve! In our engines we measure oil pressure because that is easy to do, while a flow guage would be much more expensive.
I'm with Rick and am happy to run 80psi hot, with less at idle. But I'll as happily accept that an old engine that doesn't get 'raced' will survive for years as Keith originally described.
Leave it alone!
|The oil pump is a positive displacement pump which means is capable of developing very high pressure when the discharge flow is restricted such as cold oil & tight bearings/passages. The purpose of the pressure relief valve is to prevent that pressure from getting too high, as JohnD says. |
But the valve relieves back to the sump and that flow by-passes the lubrication circut. That will continue until the oil warms up and the viscosity drops to the point where the oil can flow easily through the bearings. The back pressure then begins to drop, the RV closes, and all the oil goes through the lubrication circut.
Very high oil pressure, especially at start-up, is not a good thing.
|Brent--Thanks for an excellent description of the relief valve operation. So, switching to a different oil viscosity, say 10W-30, is the best way to lower pressure?|
Thanks for all the feedback. Sounds like this valve has little to do with increasing pressure, and is in place to relieve potentially dangerous overly high pressure. In light of all your responses, the 'if it ain't broke' adage seems to apply. Better to spend my time and $$ on things I KNOW need work.
|I have about 3500 miles on a rebuild and use Redline 10W-30. The hot oil pressure is 55-60 psi running, 25-30 psi at idle. I used Mobil 1 prior to the rebuild because of a preference for synthetics. Personally, I won't run 15W-50 or 20W-50 on anything but a very high milage engine.|
|Keith - You're correct if the RV is working right. If the spring is weak or the "plug" is worn so that it leaks, the oil pressure will be lower than it should be. The internals (spring & plug) should be renewed whenever the engine is rebuilt.|
This thread was discussed between 26/03/2003 and 27/03/2003
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