Vintage Workshop
Services for Brough Superior motorcycles and their contemporaries

KTOR valves last update: 21-05-2002

Well, I have finally tackled some of the small stuff on the heads.
The valves and springs are done now, but the rockers not yet, I am afraid...

I have been looking around for a modern replacement valve. The trouble is that most car exhaust valves have either too small heads or too thick stems.
I finally settled for a set of inlet valves made for the 2.4 l Ford engine no. 2401E (Ford Transit van 1972-84). They are made by Kolbenschmidt (have a look at their homepage on, you can download their catalogue and even search valves and pistons by dimension there!)
This is a bi-metallic valve with an austenitic head and hard chromed shaft. The product manager at the factory assured me that the same materials are used as for their bi-metallic exhaust valves. The part is KS No. 50 004 079.
The stem is 9mm and the head is 44.3mm dia against 8.72 and 44.5 of the original ones, so they would also make a perfect replacement especially in slightly worn guides!

The stem is about 15mm too long, so you can cut it and convert it to the JAP racing type of clip-and-cone spring cup fixing.

The triple springs came from the Brough Superior Club. The springs cups were out of stock, but John English still had one upper and lower cup each as a pattern, so I turned them myself.

If you need to make yourself a set, here is a drawing. Not a very nice one, but I would have been glad if I found one a few months ago!

Now, machining the little groove in the stem is not a big deal (save for grinding a 0.9mm radius tool), but the split collets are another thing!

I made them from silver steel (but will leave then unhardened).
I think it is a good thing to put the cup in the lathe chuck and adjust the angle of the top slide using a feeler gauge. You can then machine the taper of the collets to the correct angle.

But then, you have to cut the 4 slots!
I made a mandrel to hold them in the dividing head and then, using a 0.5mm slitting saw, cut the slots. 3 of them almost through, the last one to split them open at one side.

Now, this looks better yet.
No, I did not fit all of the triple springs yet, because I will have to take the valves out soon for machining the rocker bearing seats!

To be continued....  

Any kind of feedback to is appreciated
(sorry, this is not a clickable 'mailto:' hyperlink. If you want to write me, please type my address in your mailer. )

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