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Heat, Oil Viscosity and Pressure

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prb51

prb51

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Gents,
I'm looking for reassurance.
My 56 TR3 runs strong, idles well at 600 rpm (seems the 87mm pots like that better than 500)and does not burn oil.
I'm running 20w50.
In the hellatious heat of Az (112 yesterday etc.)I always get 70 psi on start up (50 psi idle) and even after the temp gauge reads 185, at least for awhile. After running at length my gauge will still indicate a bit over 185 to near 190 but that ain't bad at over 110 ambient. The car does not overheat and the cooling system is in good shape.
Anyway, after prolonged driving my psi slowly lowers to about 50 psi and my idle 25 psi.
Is this just accumulated oil heat that affect viscosity and then the pressure? Do I have any concerns?
 
prb51 said:
Is this just accumulated oil heat that affect viscosity and then the pressure?
Click to expand...
Yes.<div class="ubbcode-block"><div class="ubbcode-header">Quote:] Do I have any concerns? [/QUOTE]Not about oil pressure anyway.
 
All of my LBCs operate in that range. I've always assumed that it was normal, given that all of them do it.
 
I get the same in Southern Ontario @ 90 F. Soundsa good to me.

Andrew
 
I put in new rings (1991 cc) and bearing shells for the big ends and for the crankshaft this past spring. The shop where they honed the bores, told me to use 10W30, so I chose Castrol 10W30. For the previous 75,000 miles, I had been using 20W50 Castrol. So I used Castrol 10W30 for the first 3250 miles this summer and my pressures were just like yours. I didn't have to add any oil. I have just changed the oil and I decided to stay with Castrol 10W30. But here a hot day in summer is 85 deg. F.
 
In the dog days I've thought about using a straight weight 40 or 50 as I drive a great deal in the blow torch.
I'm amazed really that the cooling system works as well as it does (inverted TR6 fan made a great dif) but am thinking about an oil cooler but don't want to modify the small mouth apron for an airway.
For grins I tried mounting the oil cooler in tandem with the radiator (flush) and had no joy, actually a higher coolant gauge temp and same low oil pressure as I believe the oil cooler passed on too much heat to the radiator. I mounted the oil cooler'behind' the radiator with a pusher fan up front. I believe this system created a slight vacuum behind the two and impeded airflow to the extent the pusher couldn't overcome it. Fun to mess with though.
Now I just have the TR6 fan and that works as well as the electric fan did before the cooler experiment.
I'm not sure that it's worth it to modify the sheet metal (cut out below the small mouth) considering my oil pressure is the same as others experience.
 
You can always add an oil cooler with a built-in fan and mount it just about anywhere. But as long as your oil temps stay below 260 or so you'll be ok with mineral oil. If they go any higher I'd switch to a synthetic...but that's a different topic for another day!
 
Are you far from Glendale, AZ? If not, take a ride over to Ron Davis Racing. Ron built me an aluminum radiator for my TR6, to original size and specs, and that has helped my cooling problem a lot. I know that they also build one for the TR3. Might answer some questions about coolant, oil coolers, etc. that you have.
 
Bill,
I'll check that out sometime. Glendales not to far a drive.
I have an original, recored w/o start hole radiator that does quite well so can't see the expense presently but I do admire the ally rads.
 
My pressure was about the same. I switched to Redline 20w60 which holds up better in the heat, but is expensive.
I know running thick oil costs gas and horsepower, but the security of seeing higher PSI is worth it to me.
 
Bill said:
...I know running thick oil costs gas and horsepower, but the security of seeing higher PSI is worth it to me.
Click to expand...
And I'd agree, considering that both machining techniques and metallurgy have improved so greatly in the last 40-50 years. Modern engines can easily use much thinner oils and survive far longer than the early postwar designs we're running!
 
Bill,
Redline is a true synthetic Yes? Did you notice any increase in leaks after using the stuff? For some odd reason neither my front nor rear crank seals leak (maybe I'm outa oil) and I'd hate to bugger that up.
What kind of psi dif was theire with the 20/60 and what does a quart run?
 
I’m a big believer in pure synthetic oil, I run it in all of my cars.
I’ve run Mobile 1 or Redline in the TR for 5 ½ years and it doesn’t leak any more than it did when I first got the car. I also run MTL in the transmission without any leaks.
I should say that the only place my engine leaks is around the valve cover gasket which I have never replaced. If I would buy one of the silicon gaskets I’m sure that would stop.
The Redline doesn’t really get better until the oil is really hot. On the highway running Mobile 1 15w50 my oil pressure would drop to about 50 PSI at 3000 RPM (70 MPH). With the Redline 20w60 it stays above 60 PSI.
I buy the Redline by the case and with shipping runs about $110. I also change it every 3000 miles which is too often because the oil is still brown when I change it. Redline also has the needed ZDDP for our cams.
My father told me when I was first starting to get into cars that oil is cheap, engines are expensive so I’ve always been a fanatic about running good oil and changing it often.
 
Like Bill, I run full synthetic in all my car. But I use Valvoline Synpower, 20W50 in the Triumphs and 5W30 in the GM 350. I've never seen an increase in oil consumption when switching to the full synthetic, but on the first engine I converted (a well-worn GM 2.8 V6), consumption dropped dramatically from about 1 qt/800 miles to about 1 qt/5000 and stayed there for the next 150,000 miles or so. Might have gone up to 1/4000 by the time I junked the car.

But IMO, oil pressure itself is over-rated. What's important is that the bearings get a steady flow of oil, and oil pressure doesn't tell you that. It's mostly an indicator of how worn the bearings are; but running heavier oil is NOT going to "un-wear" the bearings. The TR3 factory handbook states low pressure is normal at idle, and I believe them.
 
Good points all, I've run synthetic in the Mercedes Diesel but have been reluctant to do so in the TR as I've read pros/cons etc. Mostly worried about increased leaks. I think I'll give it a shot.
 
prb51 said:
I'm amazed really that the cooling system works as well as it does (inverted TR6 fan made a great dif) but am thinking about an oil cooler but don't want to modify the small mouth apron for an airway.
Click to expand...
If your cooling system works OK and you just want to get oil temps down some; you might investigate using an oil/water intercooler. I believe they are sold aftermarket, as well as being original equipment on some Fords (Mustang GT maybe) and Volvos. As a side benefit, they also help get the oil warm faster in cold weather.
 
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