TR4/4A Triumph TR4 Oil Pressure

[SCguy]

As I continue to "break in" my engine on my TR4, I continually worry about low oil pressure. Once warm my car has about 38-40 lbs. of pressure at about 2500 rpms. I hear that this is about right. Can someone explain to me why the TR4 engine has or needs less oil pressure than my TR6? At idle it has about 15 to 20 lbs.

 

[tdskip]

To clarify - your TR4 has 15 to 20 lbs at idle when hot?

 

[TR3driver]

Does seem kind of low to me, for a freshly rebuilt engine. What grade of oil are you using ? Have you checked the gauge for accuracy ? And how on earth can you read the difference between 38 psi and 40 psi on the stock gauge ?!

40 psi @ 2500 rpm won't necessarily harm anything; oil pressure is primarily an indicator of wear. Oil flow is what is important to the bearings and the pressure doesn't tell you much about flow. But I would expect a fresh engine to open the pressure relief valve (ie 70 psi) at 2500 rpm hot.

Have you tried cleaning the relief valve ?

 

[SCguy]

Pressures are when hot. At 2500 my (newly rebuilt)gauge was reading just slightly below 40 lbs. This is an engine that was rebuilt, but then just sat for probably a decade. 20-50 with GM OES added. I've put maybe 100 miles on the engine and all sounds and feels right.

 

[TR4nut]

Larry-

Yours does sound low, I run about 60 psi@2500 cruising speed when warm, and drop to about 35-40 at idle. I did have some erratic pressures, pretty 10-20 psi at idle, but I believe that was due to a misbehaving bypass valve. Might be worth seeing if your gauge is really giving reliable numbers even though it is rebuilt.

Randy.

 

[prb51]

I've a TR3 but same engine, as you know, and the official service supplement manual with the later "full flow" oil cleaner (bypass) says one should get 70 psi @ 2000 rpm at 70 deg C. Now that's not really hot as that's 158 degrees.
On my 3 (how many miles?) if the engine is still at 158 I'm 70 psi. It will drop to 50/55 psi after lengthy driving when fully hot (20-30 miles of driving) but I suspect this is a viscosity issue more than anything (castrol 20-50).
For a 'fresh engine' that seems a bit low.
What do your start up numbers look like (mine 70 psi at 1100 rpm, 50 psi 500 rpm Idle)?

 

[SCguy]

My start up number are at least 70 psi at 1100 rpm, 50 psi 500 rpm Idle (like yours). These numbers stay high until my car has been running for about 20 minutes. Then they seem to quickly drop to the new levels and stay there.

I have a spin-on oil filter and adapter and have not yet checked the bi-pass valve.

 

[Merlin63Tr4]

Larry, your oil pressure does sound a little low for a newly rebuilt engine. On my well worn '63 (90,000 miles since last overhaul) I'm still getting 70 psig at normal operating temperatures and about 2000-2500 rpm. I'm using 20W-50 viscosity oil and still have the standard canister filter setup. This last summer I did have an incident with sudden low idle oil pressure after getting off I680 after a very long high speed run, and it turned out to be a small piece of debris in the oil pressure relief valve seat not allowing the valve to fully close. My normal hot idle oil pressure runs around 40 psig, but them my idle speed is around 850 to 900 rpm.
I did verify that my oil pressure gage is accurate by comparing it against a lab calibrated gage.

 

[TR3driver]

Don't recall where I read it now, but ISTR someone writing that they found their oil pump outer rotor to be cracked, which caused both low oil pressure and damage to the pump housing. If you don't find any other cause, it might be worth dropping the pan and inspecting the pump.

 

[Bob_Burt]

Have you tried adjusting the pressure relief valve? When I got my '58 TR-3 2 years ago the oil pressure was running about 90 # warm. I think it's the original engine with about 90 K miles. I backed-off the valve a couple of turns and it now runs at 70 # on the highway.

Maybe your valve is set too low? Simple thing to check - just back off of the nut and turn the plug in a turn or two, then check the results.

Bob Burt

 

[SCguy]

I could be very wrong about this... but doesn't the valve only correct overly high pressure. I fiddled a little with the valve but not much changed.

 

[prb51]

Messing with the valve won't raise low oil pressure. It's preset to open at 70 lbs. at the factory and that's its only function.
Bob was correct to lower his so it opened at 70 lbs but that's all it will do.
You can't improve low pressure by 'tightening' things up as it were.

 

[tdskip]

Have you tried adjusting the pressure relief valve? When I got my '58 TR-3 2 years ago the oil pressure was running about 90 # warm. I think it's the original engine with about 90 K miles. I backed-off the valve a couple of turns and it now runs at 70 # on the highway.

Too much oil pressure - now thre is a problem that I won't have to deal with....

 

[vrod]

SC guy, This past summer, I was talking to a guy who said he had to take his oil pump apart and check the clearances between the pump parts and file part of it down in order to obtain the right clearances. After he did this, he said he had great oil presure. You would have to hear from one of our other tr4 owners, to see if they have had to do this before. I am used to dealing more with the I6.

 

[prb51]

SC,
You could always drop the pan and check tolerances, change out the big ends, redo the thrust bearings.
I'm going to do that just as maint.

 

[Darrell_Walker]

Messing with the valve won't raise low oil pressure. It's preset to open at 70 lbs. at the factory and that's its only function.

But it is possible that the bypass is malfunctioning and only allowing 40 lbs of pressure before it opens.

 

[SCguy]

SC,
You could always drop the pan and check tolerances, change out the big ends, redo the thrust bearings.
I'm going to do that just as maint.

Sorry for my ignorance... What are "big ends" and "thrust bearings"? Are those the "Main Bearings" and "Thrust Washers"?

This would be new ground for me, so can anyone point me to a good write-up or get me started.

In the meantime, I'm going to continue to try and put some miles on my car in the hopes of getting a better feel for what's going on.

 

[SCguy]

Messing with the valve won't raise low oil pressure. It's preset to open at 70 lbs. at the factory and that's its only function.

But it is possible that the bypass is malfunctioning and only allowing 40 lbs of pressure before it opens.

Except, I get higher readings until the engine fully warms up.

 

[TR3driver]

Sorry for my ignorance... What are "big ends" and "thrust bearings"?

"big ends" is British for connecting rod bearings. And on a TRactor motor, I wouldn't even bother checking the thrust bearings/washers ... they will be fine. It's only the TR6 motor (which inexplicably has much less thrust surface than the TR2-4 motor) where the thurst washers are an issue.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]This would be new ground for me, so can anyone point me to a good write-up or get me started.[/QUOTE]Try the Haynes manual, ISTR it had a brief desciption of changing the con rod bearings with the engine in the car. Plus a suggestion to do it as preventative maintenance every 30,000 miles or so (which IMO is a good idea).

To check the clearance, you disassemble the bearing and lay a piece of Plastigage across the face. Then reassemble, torque, and disassemble again. Compare the width of the crushed Plastigage to the bands on the wrapper to read the clearance. Plastigage should be available at any auto parts store. You'll probably want some of both .001-.003 for main bearings and .002-.006 for rods.

A quick Google turned up this article on using Plastigage (on a Ford V8, but similar to a TR)
https://www.fast351.com/cartech/enginerebuild/index4.htm

 

[TR4nut]

I really like this topic and if you don't mind would like to ask some related questions-

If it is a worn bearing that is leading to the pressure issue Larry has, is there a likely culprit or are all bearings suspect? Just checking the big ends of the connecting rods in my mind doesn't necessarily solve the issue - is there a good way at all to diagnose where the pressure loss may be occurring other than tearing down completely? Also, how do you know it is not some other area such as top end lubrication that is the source of the problem?

For me, getting under the car and dropping the pan is okay for the pump and maybe the connect rods, but for messing with the crank mains I'm not sure I'd want to do it under the car.

Randy