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Triumph TR6 - Rocker oil feed line.

Looking for comments regards adding ricker oil feed line kits I seeing more of these days. Good & bad.
Thanks Ian.
Ian Kinaid

Ian,
If the Triumph engineers felt that this was required they would have done it. There is already a pressure oil feed going to the rocker shaft that provides enough oil for the rockers. Where they could have done better is installing bushings in the rockers! This would be the best improvement that could be made in the area other than roller bearing rockers. The other good thing to do is install a harder rocker shaft to prevent wear on the shaft. Now let's wait for all the other opinions! I really like to read everyone's ideas.
Steve Yott
Steve Yott

Ian, All,
I'm against these external oil lines, unless either you have a brand new rocker assembly and even then I'm doubtful, or you fit restrictors in the oil line in which case why bother?

The relatively wide bore external line and the low resistance pathway of the rockers could 'steal' oil flow from more important bearings lower down in the engine. In flow terms, doubling the diameter of a tube will decrease the resistance to flow SIXTEEN times - Poisueilles Law. A fluid under pressure will always go where resistance is least, so more oil could flow through the rocker shaft than the mains, big ends etc. Not what you want.


I have heard that this 'fashion' arose after Kas Kastner fitted seperate oil lines with restrictors to the mains and camshaft bearings, and the rockershaft, of his race engines. It is easy to do so for the rockers, not so for the others. No doubt he was able to measure all the pressures therein, and to adjust the restrictor size to get the pressure he wanted. Without an instrumented engine to know all the pressures we can only guess at the size of restrictor would be appropriate for a ricker shaft oil line alone.

John
JohnD

I go with JohnD. There is a huge diff. in racing were you tear down constantly and rebuild and street engines you have a panic attack with head gasket problems. Face it we all do.

Bill
Bill Brayford

Ian--I have had the external feed on for 8K miles so far in conjunction with a hardened rocker shaft. Put it on during the engine rebuild at the recommendation of my Jag/Triumph/MG mechanic (who, by the way, worked for years at TRF in their CARS dept). The oil pump has plenty of capacity to handle the additional flow diverted by the rocker feed, so I don't necessarily buy-in to the crank bearings starvation theory. Guess we won't know the long term advantage/disadvantage with this setup until it's rebuild time again.

However, I would recommend you purchase the hardened (tuftrided) rocker shaft that is available from TRF (possibly others) before installing the line. I think it's in the $70 range. It's likely your chromed OEM part is heavily worn and the benefit of the feed line would be greatly reduced due to the excess clearances.

Rick O.
Rick Orthen

I've had one on the car for several years. My understanding was the "normal" galley has a take-off to get oil to the camshaft, then goes up to the head. If there was alot of clearance in the cam, the flow to the rockers could be reduced.

As far as getting too much oil up there and robbing other bearings, as long as the oil pressure is good, all galleys will be properly fed. Also, the drilled out passage in the bolt of the "banjo" connection on the head is quite small and serves as a restriction. There have been no problems with mine, and I've not heard any bad things about using the external line.
Brent B

I've just completed a total engine rebuild at 70,000 miles largely because the car sat for fourteen years and was not stored properly. The cyl. walls were eaten away where the pistons sat. However the engine was in pretty good shape otherwise, except for the rocker assembly. The shaft and all 12 rockers were totally shot. I'm going with the external feed line.
Doug C.
D.W. Campbell

Thanks for excellent points.
As it seems an easy install. My oil pressure is already slightly on high side (hopefully not some other problem) I think I'll try it. Cars running great now. Guess I can't leave well enough alone : )
Ian Kinaid

Ian--Forgot to mention that if you get a new rocker shaft, make sure is has plugs in the ends. Some come plugged, others don't.

Rick O.
Rick Orthen

Ian,
I fear that you are misled in thinking that just because your oil pressure is 'on the high side' your main bearings will be OK.

Think of it this way. Imagine a barrel of water, with two holes in the base, one big one small. The pressure at the holes is the same. The FLOW through the holes will be very different. Worse, the barrel will empty much sooner so the pressure will drop more quickly. So may be the flow through the mains relative to the rockershaft.
(I realise that this is not a full anology - P's law refers to tubes, not holes (orifice flow is proportional to the radius, not the fourth power) and ignores the pump that maintains pressure, more or less)

IF, if your oil pump can maintain the same pressure after the external line is fitted, then maybe ok, but ANY drop will mean that the external line is stealing flow from the mains.

The above advice on a new rockershaft (and rockers?) chimes with mine, and with my experience. Use with caution (and a new rockershaft!)
John
JohnD

Hi Ian

Top end lube has been argued for decades.

From experience if your mains and other bearings have a fair amount of milage restricting oil flow which is normal you will get an increase in oil pressure for a while. Things get real sloppy and oil pressure drops. Don't panic this can take quite awhile. Years on a Sunday car.

Oil pressure for a particular engine is designed for that engine. The objective is to get enough "effective oil volume flow" to a part that moves. Oil pressure means squat other than an indicator. I understand some of the new Hondas run on 5 psi normal?

Without getting into bearing surface tech. The bottom end is taking the heavy abuse. And hardest to repair. If the flow through the bearings is restricted due to normal wear and you open up a path with the top luber as JohnD points out the oil doesn't care were it goes. And it sure will go the least restricted route. Yes they are restricted but do reduce the "effective flow of volume" to the bottom end. Pump only produces so much volume which is the concern.

I have played with Stock cars and Dragsters for 35 years with friends. 10 seconds to 20 minutes for glory or bang maybe rebuildable junk. No big deal its expected. We try all kinds of strange stuff. Thats racing.

If the TR goes bang 5 miles from home with the better halfs ice cream in the trunk your in big trouble? Thats panic!

My opinion only keep it stock. Simpler the better. Spend the time on tedious little things that make it more reliable. Save the money for a really pro rebuild when needed.

Bill



Bill Brayford

Think I will leave well enough alone after all.
Thanks for all the comments.
Ian Kinaid

Again, I've not heard of any ACTUAL problems caused by using the external feed line. I understand the concerns and the fact that part of the oil flow is redirected to the top of the engine, but in reality the effect is very minor.

The gear oil pump is positive displacement and ignoring "slip" within the pump and leakage past the relief valve, has a volumetric output proportional to engine RPM. Treating the restriction of the line "banjo" connection as an orifice, where flow is proportional to the area (the square of diameter)and the square root of the pressure drop, and under load at several thousand RPM, if an external line drops the oil pressure from 55 to 50 psig, the flow through the line amounts to a 5% change in flow distribution. So the mains have 95% of the previous oil flow. That doesn't concern me a bit.
Brent B

This is probably one of the more intersting (and controversial) threads lately. I am deffinitely not and engine mechanic and this thread has deffinitely caught my attention. We are talking engine life here! I have the line installed and went by the "hype" from the MOSS catalog. Now it appears the majority of the PROS out there are saying this is a no no. I have the original rocker shaft, oil pump, and rockers and lifters for that matter. New relief valve and spring. 56K on her. My oil pressure at running speed (warm engine)is around 40 psi. To me, this is low. Since reading this thread, I have replaced the "banjo" bolt with a solid bolt to stop the oil flow up to the top. This is temporary just to see if my oil pressure goes up. I agree with all that I would rather have good oil circulation down at the bottom. She is not back on the road yet (OK give me heck) so can not give answer yet if pressure increases. Brents' comments above are interesting. Brent, what if the engine lower end has not been rebuilt? Would you still go with the external line?
I guess the question(s) is: at what point, do you say that you have robbed to much oil from the lower end? How do you determine this? Am I further ahead to remove it (am I doing more harm than good)?
All comments appreciated.
Rick C
Rick Crawford

Rick - 40 psi is kind of on the low side. You didn't mention what oil viscosity you're using.

In general, the lower oil pressure is probably the result of worn bearings. If your're running 20W-50, a real easy fix is to replace the rod "big end" bearings. That could take the pressure back up 10 psi or more depending on how worn they are.

For info, I had an external oil line on my car for about 5 years (15k miles) before I had a rebuild at 100k. Big end bearings replaced around 80k. The machinest that did the lower engine work told me the bearings looked normal. The oil pressure at the time of the rebuild was 50-55 psig (warm). But the rings were shot, and I wanted a hotter cam.
Brent B

I just knew this would become a great thread! A couple of things to think about; (1) Cam bearings (pr in the case of the 6, the lack thereof) The pressure in the oil galley also directly feeds the cam bearings and I have found that many times a loose fit here can also cause low oil pressure! (2) We were talking about the advantages of adding additional lubrication to the rockers with the extra feed. Really thinking about this, the rest of the world of overhead valve engines stopped using rocker shafts years ago. I wonder why? I really think that with the continuous 80+ lb. load on the shaft you are going to wear it out with any amount of oil. Roller rockers would really be the best solution here and that is most likely why most race engines use them. Also, a fun point... the fist aircraft engines did not even feed oil to the rockers... They were lubed by hand oil cans on the ground. Some even used oil cups to hold a small supply! Fun stuff! Steve
Steve Yott

Ask Ted @ TSI and he will say a no way on the oil feed line. Don't remember his reason.
Don K.
DON KELLY

Adjusted my valves yesterday and noted no observable wear on the rocker shaft. This adjustment was the first following installation of a new hardened rocker shaft and external oil feed 9,700 miles ago.

Rick O.
Rick Orthen

A question about installing the oil feed line -

Where does the line connect to on the engine? (Where the oil pressure guage line connects?)

Thanks,

John Parfitt
John Parfitt

No; it connects via a kit-supplied tee fitting to the oil pressure switch port beneath the distributor.

Rick O.
Rick Orthen

As a result of this thread, I removed my external oil feed. I now see that it is a pretty small hole (restrictor)for the oil to pass compared to the mains,rods,cams,etc. I am really not sure, with that much oil moving (and trust me, I know how much - I had a frozen relief valve which blew the seal right out of the oil filter and smothered the garage in just seconds)if it could possibly cause any problem. Peter
Peter Gooch

This thread was discussed between 27/04/2003 and 09/05/2003

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