ROCKER ARM MODIFICATION

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The following article was submitted by

ALAN OSBORN ; www.aoservices.co.uk

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Racing Rockers

There follows a couple of pictures of modifications that I have done to the standard Reliant rockers, with more than a nod to 750 Racer and Dick Harvey.

A set of these has been in use for over 200K miles hence proven as reliable.

The first job to do when starting this job is realigning the rocker to the centre of the valve.

If you look at the pad that contacts the valve you will see a witness mark.

The first thing is to get this ’mark’ in the centre of the rocker so that the valve action is through the centre line of the rocker.

I think the rocker misalignment is due to ’casual’ casting procedures with the rocker.

It’s very variable, some times very little/nothing, sometimes several mm.

To align them I have used a grinder on the side of the rocker to allow it to slide on the shaft.

(Always towards the tower it seems!)

The grinding doesn’t have to be very accurate as there is no real wear on the side of the rocker.

At this point it is worth keeping the rockers in the same place on the shaft-(best practice with all engine work)

The rest of the removal of metal is pretty straightforward and obvious how to do.

The biggest drag is getting them all very similar and the time it takes on the grinder!

Not forgetting that you need to wash them thoroughly when you have finished grinding and

don’t forget to run a piece of stiff wire (heavyweight copper wire from mains cable)

through all the oil holes as well.

Then finally you use an oilstone to take the old witness mark off of the contact face.

At this point you might be considering remantling the rocker assembly.

Rocker shaft wear? This occurs at the bottom of the shaft but I do not think it is a big issue.

The wear ridge in fact helps stop the rockers flying side ways.

The springs on the shaft do not give any problems but as the centre spring is spread over a

greater distance compared to the end ones I did change it for a stronger spring.

If you reuse the old shaft take note there is many oil holes into it and through it,

clean thoroughly and use of an airline is also a good idea.

The tower also has an oil hole to be cleaned, noting that it is locked to the shaft

with a grub screw, obviously remove (do NOT lose) and service.

Unfortunately ‘tuning’ the rockers won’t give you any performance!

But it is fun, interesting and a good service is always worthwhile.

I found I removed about 15% weight.

The cam followers were also lightened while this work was going on, but with the

rest of the plot in ‘road’ trim you won’t see any change. Shame.

One point that might be worth investigating while playing here is the rocker advantage.

Having several sets of rockers to hand, I set up a dial gauge on a bench engine

and spent a happy hour looking at the amount of lift I had.

There was some considerable variation so of course I chose the best set.

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