Rocker Shafts

[chris_seven]

It has always surprised me that many people seem to build competition engines using refurbished rocker shafts.

The idea of polishing or as shown in a recent U Tube clip treating a rocker shaft with a stone just doesn't appeal.

If you reduce the diameter of the ends of the shafts by polishing the fit into the cam carrier will be affected and make them more prone to leaks or 'walking'.

Stoning the rubbing face that contacts the bush will affect roundness and I am not convinced this is a good idea.

As we have manufactured forged adjustable rockers and as we have just ordered the dies for the '906' style rocker it seemed a good idea to reproduce some rocker shafts which would have good wear resistance.

I believe that RSR Rocker Shafts were surface treated and had a Black Finish and were also expensive, they were almost certainly needed to work with the 906 style rocker which didn't have a bush and ran steel against steel.

We have had a batch of shafts made to a very high standard in terms of fits and surface finish.

We have used a high spec steel which is suitable for nitriding and have applied a Nitrotec surface finish.

We hardened and tempered the material prior to machining.

After machining the parts were 'stabilised' at 610 degC to allow any movement due to the presence of residual stress to take place.

They were then ground to final size and Nitrotec Treated at 590 degC and inspected for size.

Nitrotec is a nitriding type of process developed in the Eighties and have many benefits that seem to be the right choice.

Surface hardness is 800-900HV due to the chioce of base material.

http://www.mamesta.nl/files/Nitrotec_E%20hst.pdf

[Henry Schmidt]

Hi Chris
The rocker shafts look great. When do you expect to test them under real world application.
I look forward to seeing the results.

BTW: when we polish stock rocker shafts (generally about .0005') we avoid polishing the ends. The hope is to maintain the proper size for fitment in the cam tower.
If this mild polishing doesn't clean up the rocker or the ends show signs of wear, we just discard them.

Strangely enough, back in the day, the racing shafts were cheaper than the street version. IMS

[chris_seven]

We have a set in an engine right now.

[Henry Schmidt]

Originally Posted by chris_seven

We have a set in an engine right now.

Very cool. Any idea what they might cost?

[kenikh]

It's cruel to show this stuff and not offer it up at the same time. Cruel, I say...