Rocker shafts, wear and repair

[ncundy]

A relatively common problem I know - but what has been the common fix ?

The rocker shafts on my engine are worn - in one position (rocker 1, inlet) by 20 thou. Too bad to put back I am considering my options but would like to see what others have done before leaping in.

I have a choice of:

a) buying new (~€300 / pair)

b) metal spraying and regrinding ( I have conflicting advice on this; yes it can be done / no it can't (worried about blocking the oil feeds) and also the expense - probably as much as buying new)

c) second hand - I'm not sure I would be confident of finding second hand shafts without wear.

Any opinions or advice to help me on my way would be much appreciated.

Thanks
Neil

[Huib]

I have them remade to slight oversize and hone the rockers till they fit. There is standard shaft material of 16mm hardened on the outside. Grinding a bit off and machining the holes is not that complicated.

[ncundy]

Thanks Huib,

Some questions on making them - what material did you use, a standard hardened material like EN24, or something like EN36 which you have then case hardened and ground?

Is EN24 or the like hard enough in your experience to last ? I ask because the cost of making them in EN36 and getting them case hardened and ground is not far off the price of buying new.

As an aside I put them on a flat bed yesterday evening and one is bent ! So now I have to check all the caps, inserts and journals. It's never simple is it :S

Thanks for your help

Neil

[Huib]

I can't tell you exactly Neil. I am lucky enough to have a high tech machine shop near by which feels very much like the old local black smith where everything is possible and done with care and passion.

It is some years ago I had a batch made. The old previous owner who did the grinding (as he had done for 60 years, 6 1/2 days per week) died a year ago. I can't ask. I think he used already hardened shaft material of 16.00 mm round. I would have to measure the ones I still have in stock but I think we left them at 16.00 mm.

Fortunately the son, who already took over ownership of the company some years ago, now does the work for me like the Dunlop wheel brake cilinders and pistons, gearbox parts, oil pumps etc.. At first I thought it was not going to work as I mistakingly thought these young guys only know how to press buttons on multi million dollar NC machines. Well, they pleasantly surprised me. What they turn out on these machines is more accurate and as smooth as from grinding. They have not yet made the rocker shafts for me.

[racing]

You can use steel that we call C45 or C35. From the technical point of view you shoulden hardening
the shafts.
If i am correkt the rocker arms are hardening or in general hard.. And you should in this case on part soft
and one part hard.
It´s cheaper to pay for two shafts than for 8 rockers in case of wear.

I have the dawing for this part but as usual i don´t no where. I have to look at the weekend.

regards
andreas