TR6 TR6 oil pressure information

[ichthos]

Hello,

I have a lot to learn on this car. Maybe someone could give me a quick overview of oil pressure 101. What is the significance of oil pressure? What factors can effect the oil pressure? Can something as simple as a leaking valve cover influence it, or is the oil pressure just a functions of the block?

I have a 69 TR6. It has been running around 70 degrees lately, so I have been out driving whenever I can. When I first start up my car it shows about 75 on my oil gauge. When I am cruising down the freeway at about 70mph, it drops to about 50. When I pull off the freeway, it drops further to 25. What is considered normal for these cars? When should I worry? What factors effect oil pressure?

Any information would greatly be appreciated.

Kevin

 

[Got_All_4]

First your pressures sound fine. The only question I have is off highway at 25lbs. Is that at idle or driving at low speeds? If your driving that's a little low. Should be closer to 50.

AT start up the pressures should be a little higher say up to 90 psi until the engine oil heats up and starts to thin out. Then the pressure will drop some.

Oil pressure is created by the oil pump in the sump in the oil pan pumping oil through ports machined in the block and head to rotating parts. Such as the crank shaft main bearings, connecting rods, cam and rocker shafts. These parts have the most load or pressures on them and need the most lubrication. Bearings don't run on metal aginst metal. There are tolerances or gaps built between the bearings and the rotating part so when the oil pump is pumping, the bearings ride on a cushon of oil creating pressure. Over time these gaps increase and less pressure is created because the oil runs out easyier and this is displayed on the gauge that shows you have some internal issues. Hope this helps.

 

[Guest]

First your pressures sound fine. The only question I have is off highway at 25lbs. Is that at idle or driving at low speeds? If your driving that's a little low. Should be closer to 50.

AT start up the pressures should be a little higher say up to 90 psi until the engine oil heats up and starts to thin out. Then the pressure will drop some.

Oil pressure is created by the oil pump in the sump in the oil pan pumping oil through ports machined in the block and head to rotating parts. Such as the crank shaft main bearings, connecting rods, cam and rocker shafts. These parts have the most load or pressures on them and need the most lubrication. Bearings don't run on metal aginst metal. There are tolerances or gaps built between the bearings and the rotating part so when the oil pump is pumping, the bearings ride on a cushon of oil creating pressure. Over time these gaps increase and less pressure is created because the oil runs out easyier and this is displayed on the gauge that shows you have some internal issues. Hope this helps.

That is as good a description as any. What weight and brand (not that that matters so much) of oil product are you using? How old is the rebuild on your engine and has the oil pump been changed (and where did it come from), assuming the engine is a rebuild (whose isn't?)? I cruise at 75+ lbs and idle hot at 40 lbs. Not all aftermarket oil pumps are created equal. It seems the better ones that are available are the County brand (made in India methinks). There are some lesser pumps out there, and maybe some better ones, not sure. My last County lasted all of 5000 miles before it started to poop out.

 

[TRopic6]

Don't feel bad Kevin. My pressures are the same as yours, except I get 20 at really hot idle. I use Castrol 20W50 with no additives (STP, etc). The engine has 117K miles so I'm saving for a rebuild. In the meantime I try to accelerate smoothly so as to not throw a rod. I don't hear any knocks or rattling and oil flow seems great.

I replaced the crank thrust washers early on; there was some wear there and too much clearance can bleed off pressure. I also replaced the rocker shaft, which was badly worn.

Jeff
74 TR6 CF13816U

 

[Andrew Mace]

Kevin, I would agree that your pressures sound about right and only add that one critical point is how quickly the engine comes up to pressure. If it's more than, say, a second or two before the warning light goes out and the gauge begins to register, you've probably got issues with big-end bearings at least. But you'd likely know something was afoot because you'd likely also be hearing the classic Triumph bottom-end "death rattle" under these cold start conditions. Again, it's not fatal, but it's a good reason to investigate and do what's needed sooner rather than later!

 

[ichthos]

Thanks for the replies. Your information makes me feel better. This is my dream car, but I am on a budget. To answer some of your questions: 1) The 25 is when I am sitting at idle when I first pull off the freeway. As soon as I start to move it jumps back up to 50. 2) My car supposidly sat for over 25 years before I bought it. The car was almost totally taken a part at some point and sat in boxes (one reason the last PO decided to sell it.) The engine does not appear to have ever been rebuilt. When I first removed the valve cover it appeared to be quite clean - same with the oil pan. Also, I don't know if this a good indicator, but when I replaced seals in the gearbox I observed that the gold color on the gear selector forks were not noticeably worn. 3)I have been using 10/30 wt oil. I have used various brands. I am getting ready for an oil change. Would you recommend changing to 20/50 oil? 4)The oil pressure jumps up as soon as I turn the key and if it is cold out can be as high as 90 when the engine first turns over.

One point I am still not clear on is does the valve cover and valve cover cap have any effect on oil pressure since you mentioned the head contributes to oil pressure?

Kevin

 

[TR3driver]

IMO, with those pressures and living in Washington state, 10W30 is probably OK. If the pressures start dropping much lower, you can use heavier oil to try to compensate. But now you'd just be wasting fuel, IMO.

The valve cover & cap don't have anything to do with oil pressure; except that running the engine with them off should fling little droplets of oil all over the place. Oil should basically ooze through the little holes on top of the rocker arms, then the motion of the arms flings it around. It's not a bad idea to check for that occasionally (like maybe after setting valve clearances), since the slowly flowing oil can let the rocker shaft clog up with sludge. If that happens, the rockers & valves that don't get oil will wear faster.

Oil pressure itself isn't really all that critical IMO; it's mostly an indicator of how badly worn the other parts of the system are (bearings mostly). It's oil flow that is critical, really, and the pressure reading just gives you some confidence that oil is flowing. Obviously, if it drops to zero while driving you should stop immediately; but I've driven engines that carried less than 5 psi of oil pressure at hot idle, and they still lasted a long time after that point. Of course, it would be best to rebuild the engine before it gets that bad (and something breaks), but in my case I was planning to change engines anyway and didn't care if something broke. It never did.

 

[70herald]

The valve cover / cap have no effect whatsoever on oil pressure unless of course they are leaking so badly that all of the oil leaks away. Then you won't have any pressure /bcforum/images/%%GRAEMLIN_URL%%/jester.gif

You probably should use 20/50 weight oil. Also, while I hate to start this discussion again, but oil has changed allot in the last 30 years. Some of the additives which have been reduced were rather beneficial to engines like these with flat tappets (the thing that rub against the camshaft)
Probably the most suitable oil currently available is something like Shell Rottela which is designed for diesels and has higher levels of the anti wear additive which these engines need.
Yisrael