Rocker Shaft Orientation

Hi all with regard to the correct orientation of the rocker spindles..(inlet spidle flats rearward, exhaust flats forward).. mine are correct BTW.
I have read that the increased oil flow to the head reaches a point that the drain holes cannot cope....is this correct??
And is this event if All inlet & exhaust spindles are fitted wrongly.
The reason for asking and I'm sure it has been gone over before....with the known issues of poor camshaft / follower lubrication, is there any benefit (if possible) to purposely position one or both exhaust rocker shafts wrong to increase the quantity of oil into the pushrods tunnel??

Not only do you over oil the head the overall oil pressure including at the big ends is decreased as the back pressure from the rockers is reduced. A better oil will do more for the camshaft than more low quality oil. Hence the extensive oil test results on this site should be followed and rocker shafts left as they are.

olympus said:

Hi all with regard to the correct orientation of the rocker spindles..(inlet spidle flats rearward, exhaust flats forward).. mine are correct BTW.
I have read that the increased oil flow to the head reaches a point that the drain holes cannot cope....is this correct??
And is this event if All inlet & exhaust spindles are fitted wrongly.
The reason for asking and I'm sure it has been gone over before....with the known issues of poor camshaft / follower lubrication, is there any benefit (if possible) to purposely position one or both exhaust rocker shafts wrong to increase the quantity of oil into the pushrods tunnel??

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Have you been reading the "Camshaft Oiling Problems" in Roadholder issue No.389 by any chance as I certainly would NOT do what is suggested in that article.

No I haven't read it....can you enlighten please
The oil database is an astonishing piece of work without doubt, and to that degree the current running in oil added is from the fore mention database.
And indeed once broken In I will again take note of It
All I'm doing is asking the question and not suggesting for one minute that I'll be doing this or indeed planting the seed for others to.

L.A.B. said:

Have you been reading the "Camshaft Oiling Problems" in Roadholder issue No.389 by any chance as I certainly would NOT do what is suggested in that article.

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Just read it, a dangerous piece of work with no reference to oil pressures or the potential lower life of the big end shells. If you want to read it you will have to join the NOC and then wait for it to be added to the archive of Roadholders. It proposes you turn both rocker shaft around and then deal with the extra oil in the head by opening up the drain passageways in the cam followers. The only sensible suggestion is to weld up the cases to restore the oil trough so the camshaft runs in oil at start up.

olympus said:

No I haven't read it....can you enlighten please

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As kommando said, reversing the rocker spindles removes the rocker restriction so not only does it flood the head but oil pressure will be reduced significantly.

When the crankshaft and valve gear share the same pressurised oil supply then having one, two or more unrestricted outlets in the head is not a good idea because the increased flow from the unrestricted rockers is oil that is being diverted away from the crankshaft and with a consequent loss of pressure!

With one or more spindles reversed the oil no longer has to travel through the clearance between the spindle and rocker to escape so an area of the rocker and spindle won't get as much lubrication, and if for instance, the exhaust rockers are unrestricted then that probably starves the inlets to a certain extent.

kommando said:

Just read it, a dangerous piece of work with no reference to oil pressures or the potential lower life of the big end shells.

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Yes, I really don't know how that article made it into Roadholder.

I have read on here and seen photos of an owner who modified the crankcases to form a trough under the cam, I wish I'd seen this before putting the lump back together.
I dont like the NOC so haven't seen or indeed heard about the article until now... spooky though

L.A.B. said:

As kommando said, reversing the rocker spindles removes the rocker restriction so not only does it flood the head but oil pressure will be reduced significantly.

When the crankshaft and valve gear share the same pressurised oil supply then having one, two or more unrestricted outlets in the head is not a good idea because the increased flow from the unrestricted rockers is oil that is being diverted away from the crankshaft and with a consequent loss of pressure!

With one or more spindles reversed the oil no longer has to travel through the clearance between the spindle and rocker to escape so an area of the rocker and spindle won't get as much lubrication, and if for instance, the exhaust rockers are unrestricted then that probably starves the inlets to a certain extent.

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Path of least resistance for the oil...As I said all I'm doing is asking the question

Basic fluid mechanics, a pump produces flow not pressure, the pressure comes from restricting the outflow. This is demonstrated every time someone is either scalded or frozen in a shower when a tap is opened on the same pipe circuit.

With the current set up, flats outward, there is actually no guarantee that oil will make its way up the drilling in the rocker to the drilled ball end, the oil could just run out of the ends of the rocker on either side - path of least resistance, so the thinking behind the current spacing of the spindles is flawed. It just would not be designed like that now or in the past with a hit or miss approach to how much oil would make its was to the drilling. Considering that the hole in the ball end and thus the drilling in the rocker is shut off for a large portion of time in use, I doubt if pressure loss is an issue, Oil pressure testing was done on the NOC set up post publication with no noticeable change.

There are manuals out there by factory engineers at the time that say the the hole and or flat in the spindle faces the drilling in the rocker, some manuals say both!! There is also some interesting testing done by John Hudson who measured the volume of oil delivered to the head around the time they moved from 3 start to 6 start pump. There is also a Norton factory drawing showing a semi circle bucket tappet with chamfers both sides and drilled to let oil by - a race item, but what did the race shop spot that the other draughtsmen didn't. Considering the spindles that are out there, it seems much was done but with no real appreciation of the problem, scrolled spindles worked, drilled spindles, drilled spindles with different size flats, which realistically if 'flats outward' would not make no difference so why change the size of the flat.

The tappet gets hot, very hot in use and some may have measured it with an IR thermometer, a decent supply of oil past the tappets help would not only lubricate, but it would also help to remove some of the heat generated.

Other push rod engines like a nice supply to the top of the pushrod, some are even drilled to allow oil down to the follower.

I can find no notes on why the spindles were changed in their lifetime, I can see the change number, but we don't have the change register or why the manuals vary from flats in and out over time, the crank journal size is believed to be the reason 6 start was introduced, As for the making these changes and losing pressure, most PRV are set with one shim, just increase the shims to two or 3.

Madnorton said:

As for the making these changes and losing pressure, most PRV are set with one shim, just increase the shims to two or 3.

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That only changes the peak oil pressure ie the pressure the PRV opens at, it does not change the pressure profile shape with revs and oil temperatures below the peak which will be reduced because of the higher flow at the rockers.

Madnorton said:

With the current set up, flats outward, there is actually no guarantee that oil will make its way up the drilling in the rocker to the drilled ball end, the oil could just run out of the ends of the rocker on either side - path of least resistance, so the thinking behind the current spacing of the spindles is flawed.

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I wasn't suggesting that all the oil passes from one side of the rocker to the other with the holes on opposite sides (as they should be in my opinion) but exits from the ends of the rocker which would also be preferable.

Madnorton said:

Considering that the hole in the ball end and thus the drilling in the rocker is shut off for a large portion of time in use,

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Considering there is a flat in the spindle I would question if the oil feed is "shut off for a large proportion of time" if any?

Madnorton said:

I doubt if pressure loss is an issue, Oil pressure testing was done on the NOC set up post publication with no noticeable change.

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I don't see how it could not be an issue given the low pump feed rate and hot oil.

Madnorton said:

There are manuals out there by factory engineers at the time that say the the hole and or flat in the spindle faces the drilling in the rocker, some manuals say both!!

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Well, "both" can't be right, can it and facing inwards seems to be an error. The factory Commando manuals emphatically state that the flats should be positioned facing away from the head and included a diagram.

Madnorton said:

I can find no notes on why the spindles were changed in their lifetime,

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The early spindles were scrolled for use with the low-pressure rocker feed which is logical.

Madnorton said:

The tappet gets hot, very hot in use and some may have measured it with an IR thermometer, a decent supply of oil past the tappets help would not only lubricate, but it would also help to remove some of the heat generated.

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Maybe so, but not at the expense of directing oil away from the big ends or without uprating the oil pump in my opinion.

Madnorton said:

Other push rod engines like a nice supply to the top of the pushrod, some are even drilled to allow oil down to the follower.

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"Other pushrod engines" usually have higher capacity pumps and often have a 'feed restriction' to the valve gear in one form or another.

Madnorton said:

As for the making these changes and losing pressure, most PRV are set with one shim, just increase the shims to two or 3.

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The average Commando oil pump has difficulty even reaching the OPRV blow-off pressure when the oil is hot so adding shims isn't the answer.

The oil system with the flats outwards works well enough for rocker lubrication and no reason to change it although we've had several incidences reported here where the rocker spindles have been found incorrectly fitted and the problems caused by it.


And, you've done or intend to do this modification to your own Commando?

Madnorton said:

With the current set up, flats outward, there is actually no guarantee that oil will make its way up the drilling in the rocker to the drilled ball end, the oil could just run out of the ends of the rocker on either side - path of least resistance, so the thinking behind the current spacing of the spindles is flawed. It just would not be designed like that now or in the past with a hit or miss approach to how much oil would make its was to the drilling. Considering that the hole in the ball end and thus the drilling in the rocker is shut off for a large portion of time in use, I doubt if pressure loss is an issue, Oil pressure testing was done on the NOC set up post publication with no noticeable change.



Other push rod engines like a nice supply to the top of the pushrod, some are even drilled to allow oil down to the follower.

I can find no notes on why the spindles were changed in their lifetime, I can see the change number, but we don't have the change register or why the manuals vary from flats in and out over time, the crank journal size is believed to be the reason 6 start was introduced, As for the making these changes and losing pressure, most PRV are set with one shim, just increase the shims to two or 3.

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You don't think oil gets to the pushrod cup? OK, as an experiment, remove one rocker in your head, then drive the ball out and refit it with the hole in the side facing away from the drilling in the rocker arm.

Refit and run your engine for 20 minutes

Just make sure you have a replacement pushrod for when you have to take the head off again to repair it, and re-orient the ball in the end of the rocker to get the oil flowing back down the drilling in the rocker arm to the pushrod cup. You'll only need to do it on one rocker, so you have a direct comparison.

I saw the rh article , what caught my attention was the modification to the cam lifters to improve oil flow.. but whilst that might give marginal relief to an over oiled head, the cam,surely, gets its oil from crankshaft fling as pointed out on here , cold starts might be different , so possibly worth doing for that . and pouring oil down exhaust rocker covers, but I would leave the rockershafts alone and as per factory set up.

Oil pressure gauges ho hum.. Mine gives a healthy 60 or more with cold oil but it drops off pretty fast as the engine warms up. My opinion is not to worry too much about a low figure , the factory stopped fitting gauges . Most of the big end pressure is generated by centrifuge effect of the crank

what would concern me is a sudden enexplained loss of op when cruising at 70 or 70 ++ ,not the low reading you will get afterwards at traffic lights,

I have cured several engines of low oil pressure by installing the rockershafts the right way round. Of course the pump, opv and seals etc is checked/repaired/replaced before. If pressure is still low, the big ends are worn completely or the rockershafts are worn or wrong way round or both. Perfect condition of everything will give you over 80 psi on cold start up and at least 8 psi per 1000 revs when hot. Worn oilpumps and misadjusted opvs will only deliver half that pressure so I don´t think a motor in this condition will survive a long time with shafts turned around....

oldmikew said:

Most of the big end pressure is generated by centrifuge effect of the crank

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Has an affect yes....but most???
Please enlightened us

Seeley920 said:

You don't think oil gets to the pushrod cup? OK, as an experiment, remove one rocker in your head, then drive the ball out and refit it with the hole in the side facing away from the drilling in the rocker arm.

Refit and run your engine for 20 minutes

Just make sure you have a replacement pushrod for when you have to take the head off again to repair it, and re-orient the ball in the end of the rocker to get the oil flowing back down the drilling in the rocker arm to the pushrod cup. You'll only need to do it on one rocker, so you have a direct comparison.

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I don't say that, 'no guarantee' is what I typed.

MK3 manual could cause confusion, if not read to the end of the section. Manuals produced at the time when the flat on the spindle was introduced says inwards.

Considering how the rocker rotates, does the flat does reach far enough around the radius to ensure that the hole in the rocker is exposed to the flat throughout its entire operating angle. I doubt it.

The rocker spindle flat was extended along the spindle, not wider so as to increase its arc, why? when it faces away from the rocker, anyones guess. The scrolled spindle may have had a flat at one stage, The flat was an addition to the plain spindle, it then change in dimension.

What did the race shop spot to produce a tappet that was double chamfered and drilled to let more oil past, sadly nothing can be found to say what spindles they were using.

The oil pump will deliver a huge volume of oil very quickly as some have found out the wrong way. The crank by its action will drive an oil wedge in the brg shell, but still needs oil to do so. Once worn, it does not matter how much oil pressure you have if the wedge of oil can't be maintained.

More questions than answers, but anything that gets more oil over the cam and over hat hot spot is a good thing. I will try it next time, I have plenty of spares.

Madnorton said:

MK3 manual could cause confusion, if not read to the end of the section.

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The Mk.3 manual says the same as the previous manual: "Engage a rocker spindle into the cylinder head with flat facing rearwards on the inlet side and forwards on the exhaust...."
.
.
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Note: Flat on spindle faces away from the centre of the head, towards rocker cover."

I don't know how anyone could be confused.

Madnorton said:

Manuals produced at the time when the flat on the spindle was introduced says inwards.

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And which is obviously wrong as later manuals don't say that. Even the early version Commando manual states: "The correct location of the rocker spindle is with the oil hole facing away* from the centre of the cylinder head."

*(bold italic as printed)

Madnorton said:

The scrolled spindle may have had a flat at one stage,

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May have but it doesn't now, and wouldn't need one with a central groove and scrolling so if there was an earlier spindle with a 'flat' then it would seem to be for the low-pressure rocker feed requiring a different orientation and possibly the reason for the apparent error in the pre-Commando manual.

Madnorton said:

What did the race shop spot to produce a tappet that was double chamfered and drilled to let more oil past, sadly nothing can be found to say what spindles they were using.

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Seems little point mentioning it then.