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ROCKER SHAFT END CAPS ADVICE


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Good afternoon everyone. I am about to undertake overhaul of the rocker gear on my 1964 TR4  and wondered if there is any reason why I shouldn't use split pins instead of Mills pins to secure the end caps to the rocker shaft. It appears to be standard on 6 cylinder engines. 3/32 size appears to fit the larger engine. Same size holes on 4 cylinder?

Many thanks in anticipation     Willie

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Hi Willie,

both my 4A and 4 have split pins on the end caps.  The 4A for over twenty years.

I suspect a concern could be if vibration caused the split pins to vibrate and fret causing them to drop out and the cap falling away.

However the serious lubrication in that area would stop any fretting.

 

Roger

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This all depends on if you have plugs inside the ends of your rocker shaft.

Original shafts do not have internal plugs and the end caps, which seal the ends of the shaft tube are retained by solid pins;  that create an oil seal where they are pushed in the end cap holes.  Split pins will not form an oil tight seal in the end cap.

I have seen repro shafts that have internal end caps in them from new.

So, check your rocker shaft for internal end caps if you intend to use split pins.

Peter W

 

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Oh dear, should I be worried Peter. I fitted a replacement rocker shaft some 20,000 mile ago, it was a hollow tube with no internal end caps. I replaced the Mills pins with spilt pins simply for convenience. Why is it an issue if a little oil seeps from the end caps because spilt pins are not oil tight? Surely there's still plenty for the rockers.

Tim

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11 hours ago, BlueTR3A-5EKT said:

This all depends on if you have plugs inside the ends of your rocker shaft.

Original shafts do not have internal plugs and the end caps, which seal the ends of the shaft tube are retained by solid pins;  that create an oil seal where they are pushed in the end cap holes.  Split pins will not form an oil tight seal in the end cap.

I have seen repro shafts that have internal end caps in them from new.

So, check your rocker shaft for internal end caps if you intend to use split pins.

Peter W

 

Peter, thank you for that information!

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4 hours ago, tim hunt said:

Oh dear, should I be worried Peter. I fitted a replacement rocker shaft some 20,000 mile ago, it was a hollow tube with no internal end caps. I replaced the Mills pins with spilt pins simply for convenience. Why is it an issue if a little oil seeps from the end caps because spilt pins are not oil tight? Surely there's still plenty for the rockers.

Tim

Hi Tim,

don;t panic. Mine has done far more than that and still going strong.

The lubrication to the rockers is not excessive so oil loss is not the best thing to have but it works.

 

Roger

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Hi Folks,

                There are indeed internal plugs to my new rocker shaft.  I am going to strip the shaft, but I noticed this morning that the front double coil washer looks as if it is broken. Lots of free movement whilst everything is still on the head. Not opened it up yet as leaving till next week when my son will be in Hereford. He will take the car one day so I want to do the overhaul with him present!  The washer [part 044630] seems to be out of stock everywhere. Does anyone know of a suitable substitute - or a source of supply!  Also the end caps [060733] in case I have a problem removing the pins.  Incidentally, do the pins only push in one way? I can only see one end!  Does one drill them out?

Willie

10. #1 rocker on shaft.JPG

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Hi Willie, don't drill them out, the roll pins are split along their length which provides tension to hold them in place, the end you can see is probably the end it was knocked in from. Remove with a hammer and suitable punch from other side.

Chris

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Mills pins do tend to be tapered at one end so find the smaller end and tap back through from there.

Stuart.

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Sorry, allow me 2 questions:

- in the rocker shaft the oil is full or reduced pressure?

- isn't there a pressure reducing small drill in the cylinder head?

Ciao, Marco

Edited by Z320
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23 hours ago, Z320 said:

Sorry, allow me 2 questions:

- in the rocker shaft the oil is full or reduced pressure?

- isn't there a pressure reducing small drill in the cylinder head?

Ciao, Marco

 

I would suspect the oil pressure to be reduced at the rocker shaft as the oil feed gallery drops from 1/4 to 3/32 at the inlet to the rocker pedestal.

The main oil gallery is 5/8" bore

Oil feed into head from the block/cam bearing is 1/4"   

The outlet in the top surface of the head to rocker pedestal is 3/32"  This must be the restrictor.

Bore of pedestal is 1/8" Feed into rocker shaft is 9/64"

The outlet to the rockers in 8 places are 1/16"

The rockers all have a 1/16" outlet from the bearing area to rocker box/atmosphere.

Now someone with maths could work out the the pressure at the rocker shaft - but will have to make some sweeping assumptions about flows and losses at the other outlets from the main oil gallery.  Assume main oil pressure is regulated to 70 psi at the oil filter.  I do not have a flow rate for the oil pump, which is constant pressure type not constant flow due to drive speed changes.

All my dimension are in inches and were measured using drill shanks for sizing.

Someone could rig a couple oil pressure gauges/sensors.  One on the back of the head (UNC blanking screw) and one on the rocker shaft to pedestal retaining screw (Do not know thread but it is fine) on No 4 pedestal. The main gallery oil pressure could be read from the car pressure gauge or fit an another sensor/gauge into the main oil gallery. (UNC blanking screw) Then run the engine at differing speeds to note pressure changes.  Be prepared to get oil everywhere under the bonnet if you do it with the rocker cover removed though.

Cheers

Peter W

 

Edited by BlueTR3A-5EKT
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I may be missing something but, the oil pressure gauge reads 60 or 70 psi and it has a small inlet, I would of thought it’s the outlets back to the sump which determine the pressure at any given point. Therefore pressure at the rockers is determined by clearance between the rockers and the shaft and any other outlets like the endcaps, too many oversized/unwanted outlets would result in a drop in pressure to the rockers and your in trouble!

Chris

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With the pressure gauge there is no flow, therefore the size of pipe / inlet restriction whatever you want to call it will not alter the pressure at the gauge - it just may take a bit longer to get there. At the rockers there is flow, & so any restriction will reduce the pressure, and the more leaky the rocker bushes are the lower that pressure will be.

Bob.

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Why did I ask that:

if the flow to the rocker shaft is reduced - and with this the pressure in there,

it is no problem for the bearings of the crankshaft and camshaft to loose some more or less oil on the rocker shaft.

At last it will be simply the best to fix the cap the way Triumph did it - with a mills pin.

 

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What we are concluding is that the rocker shaft must be sealed at both ends. 

Either by the original caps with solid pins if the shaft has no internal plugs or if the replacement shaft has internal plugs that seal the shaft;   the end caps can be secured by split pins or roll pins as they are not required to form part of the shaft oil seal with the end caps. 

The end caps locate the rockers Nos 1 & 8 with a double coiled flat spring washer.  Those washers could be replaced by solid correctly sized shim washers, in much the same way as the springs are replaced by tube spacers.  This all requires selective assembly and time.

 

Cheers

Peter W

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1 hour ago, BlueTR3A-5EKT said:

What we are concluding is that the rocker shaft must be sealed at both ends. 

Either by the original caps with solid pins if the shaft has no internal plugs or if the replacement shaft has internal plugs that seal the shaft;   the end caps can be secured by split pins or roll pins as they are not required to form part of the shaft oil seal with the end caps. 

The end caps locate the rockers Nos 1 & 8 with a double coiled flat spring washer.  Those washers could be replaced by solid correctly sized shim washers, in much the same way as the springs are replaced by tube spacers.  This all requires selective assembly and time.

 

Cheers

Peter W

Exactly

Chris

 

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1 hour ago, Z320 said:

I do not have and do not want that,

but what about the external oil pipe to support the rocker shaft with extra oil.

Is this oil missing the the crankshaft?

It is felt that the external rocker shaft oil feed on a TR5/6 engine will rob the crankshaft of oil supply, unless a restrictor is added to the supply pipe.

Someone who knows more about this will no doubt comment.

This subject has been covered and discussed in the 6 cylinder areas.

Pumping more oil into the rocker area may flood the valves and valve guides causing oil use or smoking plus it may reduce available oil in the sump.

Peter W

Edited by BlueTR3A-5EKT
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