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Rocker shaft


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On 1/3/2021 at 2:31 AM, AarhusTr6 said:

The rocker shaft, what do the grooves cut on it do, is it to help oil get around?

Depending on what grooves you mean, they may simply be wear. If they are where the rockers sit (and aren't flats as Waldi mentions) that's most likely. Replacement sounds like a good option.

John

Edited by JohnC
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  • 3 weeks later...

Hi there,
Every cylinder head overhaul also includes overhauling the valve actuation. I always recommend a new rocker arm shaft.
Remove the fasteners and check the inside for dirt.
Rocker arms can be reground, the radius is 8 mm
Then polish the valve surface.
As long as the hole for the rocker arm shaft is still good, the rocker arm shaft and the rocker arm should now be nitrided. I've been doing this for many years on all reconditioned cylinder heads.
Even after more than 100,000 km there will be no more signs of wear.
Always nitride new rocker arms.
Unfortunately, like crankshafts, rocker arms and shafts, they were never hardened. A huge mistake! And still present today.

See you
Ralf

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Hi Ralf,
I think the tips of the rockers are (insert?) hardened. When I dressed them during my rebuilt they appeared to be very hard.

Several suppliers sell an “uprated” shaft that is harder, here is the Moss version.

Gruesse,

Waldihttps://www.moss-europe.co.uk/rocker-shaft-tuftrided-tt1217.html

 

Edited by Waldi
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Hello Waldi,
in the last 40 years I have never had a rocker arm hardened by Standart Triumph / Leyland in my hand.
Even when they were still available as an original spare part.
The nitrided rocker arm shafts sold by Moss / Rimmer etc. should be used with great care.
Why ? Because the holes were partially blocked.
Gas nitriding no problem.
Salt bath nitriding can cause problems if not properly rinsed!
I often had to clean the latter in an ultrasonic bath for hours.
That's why I always buy the rocker arm shafts raw and then have them gas nitrided together with the rocker arms.

See you
Ralf

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Thanks Ralf,

I will double check my tuftrided version. Tuftriding is done in a salt-bath....good heads-up.

Waldi

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Waldo and Schnippel here's some information you will find interesting. I recently contacted Moss to find out the hardness of the rocker arm tips they sell. Within the past two weeks this  attached photo is an arm I paid to be tested and is now in my possession- I think you can safely say these rocker arms are high quality and certainly going to last - no nitriding necessary guys- Moss in their own write up say they have invested considerably in the production of these rocker arms and this photo proves the point- no pun intended. The Rockwell C scale for hardness is higher than original Triumph parts.

image001.jpg

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Interesting info there on the hardness of Moss rocker tips. 

Obvious questions: What is the hardness of original rocker tips? And if the originals are ground say 0.010", does the hardness change?

Ed

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Thanks Ralf,

I will double check my tuftrided version. Tuftriding is done in a salt-bath....good heads-up.

 

Michael,

66 HRC (if that is what I see) is “rock-hard”. I hope it is only the outer surface, not full depth, otherwise it very brittle and will be prone to failure from fatigue started from for example small surface imperfections.

Cheers,

Waldi

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That sets an interesting conundrum.

Rockwell C has a load of 150Kg - that is not superficial  So is it hardened full thickness.  Preferred not to be.

Usually case hardened items having a superficial hardened coating would be tested with 1 or 2Kg may be 5Kg. This keeps the measuring to the hardening not the overall hard/soft combination

Most rocker arms are hardened adequately. When you see what appears to be wear it is usually where the valve stem has pushed the hardened material into the softer parent material.

 

Roger

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On 1/24/2021 at 12:27 AM, ed_h said:

I think the originals had welch type plugs.  You can drill one of them,  then knock them out from the inside with a long rod.

Ed

Hi Ed

so I'd knock the plugs out, clean and then need to find suitable new plugs then,  Thanks, Richard

 

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This is a useful source for core plugs - Sorry it is in UK.  They may have the imperial size you are likely to want.

https://enginecoreplugs.com/product-category/imperial-core-plug-cup-type-freeze-frost-expansion-welch-cap-lid/

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