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Oil pressure

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HarryL

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Just cranked the baby over after a 4 year frame off
and the pressure came up quickly ! Whew.
Went to 80psi before the relief valve kicked in.
Have to adjust the pressure. Anyone know what's the average
decrease on a turn. CCW I presume.
Tomorrow comes the petro and more fun
Harry
 
A tr4a. Using 20-50 Valvoline for break in. If it goes to 80psi spinning
the engine with the plugs out; reason would say the pressure needs to be adjusted.
Don't want to wash a bearing out.
Harry
 
Bob, just curious, what is the regular oil you suggest? I've seen a lot of suggestions for 20w50.
 
If the valve opened at 80, then I wouldn't worry about it. The exact value is simply not that important.

If you must worry, first thing would be to double-check the calibration of the gauge. They weren't all that accurate new, and after 45 years it's more amazing that they work at all.

You could try going one step lighter on the oil (10W40 or even the book recommended 20W40 if you can find it); but 20W50 should work fine. That's what I run year-round, and you're farther south than I am.

"Back when", I tried running straight 40 weight in the winter in a freshly rebuilt engine. Pegged the gauge every time I started it cold; but no other problems. The thick oil did make it hard to crank though, so I eventually switched to 10W40.
 
I have been using Castrol 10W30 in my 1958 TR3A for the last 7 summers - since I rebuilt the engine. I have had no issues of consumption, oil pressure, etc. during these last 14,000 miles During the previous 94,000 miles I was using 20W50 after rebuilding the engine at 80,300 miles from new and got lots of blow-by on the "new" engine and dripping oil from the bottom of the crankcase vent pipe which drips just below the fuel pump. During those 94,000 miles, I had to add a quart of Castrol 20W50 every 600 miles or so. Oh yes, I'm adding 4 oz. of ZDDP plus every full oil change (3000 miles) and I add 4 oz. of Marvel Mystery oil or Lucas upper cylinder lubricant to ther gas tank at every fuel fill up as suggested in all the early TR manuals. In your case, I'd go for the 10W30 and see what your oil mileage is. You probably will not need to fiddle with the by-pass oil pressure adjustment either. I "feel" that the 20W50 oil might be leaving too thick an oil film on the cylinder walls - while the 10W30 gets "swept" off better by the oil rings - hence better mileage out of the oil. BTW, I never have to top up the oil between 3000 mile oil changes on the present engine with 10W30.
 
On a new, tight engine, I always use thinner oils. Better mileage, easier cranking, etc. We always saved the heavier oil for an old, tired engine that would not hold oil pressure at idle.

I can't think of any reason to use heavy oil in a fresh rebuild...won't hurt anything, it's just fighting a lot of viscosity you don't need.
 
Good points mentioned here........I would also agree.

CJD said:
On a new, tight engine, I always use thinner oils. Better mileage, easier cranking, etc. We always saved the heavier oil for an old, tired engine that would not hold oil pressure at idle.

I can't think of any reason to use heavy oil in a fresh rebuild...won't hurt anything, it's just fighting a lot of viscosity you don't need.
Click to expand...
 
As a point of reference, I run Brad Penn 20W50 in my TR4A. I see about 80psi at startup, and between 40 and 60psi after the engine oil is up to temperature. i think that is near perfect, so I would do no adjusting of the PRV, until you've seen what the oil pressure does after a good run in.

Also, the discussion of heavy weight vs. light weight oils has me a little baffled. There isn't all that much difference in cold viscosity between a 20W50 and a 10W40 oil. Both are considerably "thinner" than the 30W oil these cars used when new.
 
Thanks Guys,
Going to leave the oil pressure alone.
Trying to sort out a timing problem at the moment !
Harry
 
TR4A_IRS said:
Also, the discussion of heavy weight vs. light weight oils has me a little baffled. There isn't all that much difference in cold viscosity between a 20W50 and a 10W40 oil. Both are considerably "thinner" than the 30W oil these cars used when new.
Click to expand...

It's my understanding that you are correct when the oil is cold...as that is the significance of the lower number in a multi-viscosity oil. The higher number is the equivilancy when hot. So they are more viscous in a warm engine than the straight 30w.

I always ran straight 20w in my performance engines.
 
John, I agree with you. I think the OP was seeing high oil pressure right after startup, which is where the "cold" viscosity comes into play. It's my opinion that we are very lucky to have a large selection of muti-weight oils to choose from, as the old single weight oils were a definite compromise between proper lubrication at startup and in a hot engine. My 2012 Mazda uses a 0W20 synthetic oil (at least, that is what I put in it), but it is built to much tighter tolerances than our LBCs were. I feel better with a higher "hot" viscosity oil in my TR, as it probably needs all the lubrication I can give it, when its running at temp...
 
TR4A_IRS said:
... My 2012 Mazda uses a 0W20 synthetic oil (at least, that is what I put in it), but it is built to much tighter tolerances than our LBCs were. ...
Click to expand...

It seems that all the manufacturers are going to lighter weight oils, and although factory tolerances are tighter then years ago, the primary reason for this is fuel economy. In order to meet CAFE standards, car manufacturers are using everything that they possibly can to squeeze out even just tenths of an MPG.

I use either 10W-40 or 20W-50 in the TR3.

My '07 RX-8 uses 5W-20, and my wife's '11 Mazda CX-7 uses 0W-20. And from what I've read, most manufacturers are going the same route toward light oils.
 
I'm in CT and run 10W40. It's a bit high when the engine is cold (~85-90psi) but when hot it runs a nice 75psi at 2000 RPM. I had tried the 20W50 in the past but the pressures were higher. It was mostly the cold pressure at 100+psi which didn't sit well with me

Bob
 
Had a hard time but got the baby sorted out today and the engine is purring like a kitten !
Everyone needs a laff so here it goes- the timing was 180 off ! This is about my
10th engine rebuild and 8 of them have started off with the same issue- go figure.
Ran it up to 3k for a bit ; not keeping revs steady for long. Settled it
down to around a 1000 & adjusted carbs. Oil pressure stayed between 70-80
with minor fluctuation. The heat paint burning off the headers sure smelled good !
Fuel guage is the only issue at the moment.
Have a great weekend motoring
Harry
Only oil leak at the moment is off the rear of the valve cover.
 
Don't feel too bad, Harry. I just "fixed" my high oil pressure by removing an extra o-ring on the oil filter canister. I never saw the old one tucked up in there. Oops. Lesson learned. I'm running 20w50, btw, and the pressure is higher than what was in there previously, but still in the 70-80 range cold, so I'm not complaining.
 
Great
Was going to take it thru the neighborhood; but the master cylinder on the
clutch was toast. Tried rebuilding both master and am going to order both new !
Just some more money ! Still have much to do.
Last major concern is the clutch.
Harry
 
SMGoose said:
Don't feel too bad, Harry. I just "fixed" my high oil pressure by removing an extra o-ring on the oil filter canister. I never saw the old one tucked up in there. Oops. Lesson learned.
Click to expand...
Scott, you're lucky all you had was (too-)high oil pressure! I did the same thing once on a GT6 engine; unfortunately for me, the double-o-ring resulted only in several quarts of oil on the blacktop driveway of my parents' house! :nightmare::nightmare:
 
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