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E: Engine Modified Rocker arms

Bill Thomas

Well Known and Active Website User
VOC Member
Interesting to me, Trying to help a friend with valve problems , I was trying to say how I grind a Rocker Arm,
When using a locking feed bolt, Looked at it on VOC Spares for a photo and found they are now supplied already ground !!,
I thought it was worth showing. Cheers Bill.

stu spalding

Well Known and Active Website User
VOC Member
Hi Bill, I've posted this pic before but if the new rockers are anything like the front one then far too much metal has been removed, in fact it allows for over an inch of valve travel, totally unnecessary. The rear rocker rocker in the pic shows how little needs to be removed. Cheers, Stu.


  • 5   Rockers.JPG
    5 Rockers.JPG
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Bill Thomas

Well Known and Active Website User
VOC Member
Thanks Stu, Must admit the last one I did I think I ground MORE !.
I am not good with numbers, Tend to work by feel and eye, Well one of them :D .
With the different cam lifts, Mk2 and 105, And how deep the valve seats are cut, Valve bounce etc,
There is a lot to think about ?.
I am sure the locking R/Bolt I made in the 70s Didn't need any grinding of the rocker,
But maybe I am wrong.
I know I am out of touch, But wonder how many people have fitted Locking feed bolts,
To old rockers, Without grinding, And have had trouble ?.
Cheers Bill.

Marcus Bowden

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VOC Member
I think it was 1965 or 66 when I made my first set (in MPH) and was stationed in the main factory working on a big Denham lathe about 15 feet long with my fitter instructor Mr Scot (King Rag, he would keep walking behind me and pick up items I had machined, he felt a raggy edge he would cuff me round the ear) working a slightly bigger lathe next to me that he had worked all the way through the war.
Material EN 100, what they make Allen bolts from and I still use them as I have an abundance of Allen bolts when Harvey bought the factory next to his own and we had such a choice of machinery to remove and stores in 2001.


Well Known and Active Website User
VOC Member
We did not have the ET100 mod back in the day its almost universally adopted now perhaps that has a bearing (pun!) on the changes. I certainly have ground a few tops to get the range of movement

Bill Thomas

Well Known and Active Website User
VOC Member
No, But like Marcus I made my own, Tried the long bushes, No good for me,
I see they are in the Spares company too !.
It pays to Check what the Spares Company have done,
Like, I didn't know they did long Clutch cables with the nylon inners till the other day when it was on the Forum.
Maybe it would be good for the Factory to Post What and why the Mod's have been done,
Maybe one a month ?.
Sorry I know it would take a lot of time, But may get an increase in sales ?.
I can't be the only one out of touch ?.
Cheers Bill.


Well Known and Active Website User
VOC Member
I believe that it is the nut that needs to be ground down to a "knife-edge" on both sides. This eliminates much of the grinding on the rocker arms themselves. It is the rocker that is hitting the locking nut that causes much of the clearance problem.


Stock on the left, fitted for clearance on the right.

The matching rocker arm is at the top of the photo.


I installed the modified rockers in the engine I built for David Tompkins in 2018, which has run well to date, redlining at 7,000 RPM.


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