MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

TR parts and Triumph parts, TR bits, Triumph Car Spares and accessories are available for TR2, TR3, TR3A, TR4, TR4A, TR5, TR6, TR7, TR8, Spitfire and Stag and other TR models are available from British car spares and parts company LBCarCo.

Triumph TR6 - Roller rockers and oil pressure

I just rebuilt a 73 TR-6 engine. All the bottom end bearing clearances and cam to bearing clearance are within specs. I installed a new oil pump, pressure relief valve, and spring. I removed the valve cover and observed the oil drip from the rockers @ idle. It doesen't drip it pours 12 streams of oil from the rockers. The oil pressure at hot idle is approx 10psi or just above. At 2500 RPM it's about 45. This is too low for a fresh engine. By the way, the engine also has an external pressure oil feed line for the rocker shaft. I know that roller rockers are used on British engines frequently. Is the oil leak at the rockers normal for roller rockers? What can be done to counteract this?

Does anyone know how to degree a TR-6 cam with standard sprockets?
Gary Miller

Hi Gary,
Im not sure what you mean by roller rockers -roller rockers are not standard on tr6s. Do you mean that the rockers rotate or are mounted on a shaft as opposed to studs? I cant answer your question about how much oil should be coming out of the rockers.

If you havnt done so allready you may be able to increase oil pressure (or alternatively understood decrease pressure loss)by reducing the clearance between the oil pump vanes and the top housing (flat piece of glass and wet/dry sandpaper works). You can also try get an uprated pressure relief spring too. Again if not allready done you can lap in the pressure valve to make sure its a clean fit. Maybe weight of oil is a factor: book specs 20-50 weight.

Re degreeing - lots of info to be had on the web.
regards
Michael

Actually that oil pressure is not unreasonable. My engine has a year on it. With an oil mixture of what is 2 parts 10w-30 to 3 parts 10W-40 (10W-37?? don't even ask), the hot idle pressure is probably 15-20 psi, and 45 psi at 2500 rpm. I don't really worry about the idle pressure because the engine is at minimum speed with no load on it.

Who made the roller rockers? A thin stream of oil can be very little sometimes, unless it's going on your garage floor. Seems like you can never get it all out of the can/bottle when you add it. Again, if you have decent oil pressure at speed, what's the worry?

Yeah - lots of info on degreeing cams. I did mine (several times to be SURE!) with the engine out of the car, but it can be done with a little extra hassle with the engine in.
Brent B

Hi Gary
I think it would be worthwhile removing the external oil feed to the rockers, it sounds as if all your oil is taking the easy route up there.
Your oil pressure is way too low for a newly rebuilt engine, I would be looking for 25/30 at tickover and 60+ at running speeds.
Ron
R. Algie

I've a similar set up with similar problems, yet to resolve it, but at tickover with the low oil pressure you will start to run the bearings, look in the oil filter for the glint of metal! Playing around with springs and washers on the pressure relief valve doesn't seem to help. I have been told to lap the valve in as I didn't do this on the rebuild. I have yet to check the rockers but I don't have an external feed pipe there. So I am still puzzled.


Mike G

I don't have a problem with low oil pressure at idle (is that "tickover", or is that when the starter motor is operating?) because the engine is at essentially the "no load" condition. What do you think is worse for bearings - idling at no load with a small oil film, or jamming at full load at high RPM with some oil film?

Bearings are going to wear out, can't get around that. That's why you tell your machinest to put in the BEST bearings there are when you do a rebuild, then run the best oil you can afford afterwards.

I've not heard of lapping in new oil pressure relief valves - I thought the base (seat) in the block was harder than the stem, which is why the stem is always worn. If you do lap it, be really careful. You don't want ANY of the abrasive compound to remain in there. Talk about opening up bearing clearances.....
Brent B

As a point of information and curiousity...

What clearance (or squish) did you have when you used "Plastigauge" during assembly?

I've always subscribed to the theory that I'd rather have things a tad on the tight side (of the acceptable range for clearance) and carefully break-in as required.

Just a thought.

Jim
Jim Deatsch

I had read previously that an external oil line to the rockers, which is supposed to help keep the rockers from wearing due to a lack of oil (especial under racing conditions), can cause the bottom end to be starved of oil. The streaming of oil from the rockers could be caused by a worn rocker shaft or worn rockers. Even though your engine is freshly rebuilt, was the rocker shaft and each rocker checked for wear? It sounds like this may be your problem. I agree with the other posts that recommend removing the external oil line.
R.C. Blair

This was a hot topic here about 6 months ago. I disagree with the bottom end starvation theory based on the size of the hole in the bolt that threads into the head. That's going to be a restriction. Based on some calculations and my recollection of the pressure change after installation (about 5 psi), the oil loss to the bottom end was not significant.

But the proof to me was that after running the rocker feed for at least 5 years the bottom end bearings were found in pretty good shape during last years rebuild according to my machinist.

Brent
'73 TR6
Brent B

Not that this matters, but in the archives there is a thread about how oil flow is more important than oil pressure. Higher oil pressure robs horsepower and causes higher oil pressure. Honda runs at 10 PSI new and 5 with wear. As long as I'm not on the 0 pin and I don't have knock, I'm not going to worry about it.

I've got the external feed and have no issues with it. The pressure is slightly lower than without the feed, but well within acceptable limits.

DonH
'74 CF19053U
D Hasara

Not higher oil pressure, I meant to say oil temperature...
D Hasara

If your rollers ride on needle bearings, you can expect to see much more oil flow. Rockers that are simply bushed will flow a lot less, resulting in higher PSI.

Rick O.
Rick Orthen

This thread was discussed between 18/09/2003 and 23/09/2003

Triumph TR6 index