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Series 'D' Specific ET24/6


Well Known and Active Forum Website User
VOC Member
I have 2 x ET24/6 Breather Caps one is Deeper , I am looking for another Deep version to
Clear the Valve retaining Cap ,
This is on a TPV Head

Peter Holmes

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VOC Member
Well it might, but you might not have much thread left to attach to the cap to the cylinder head.
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Well Known and Active Forum Website User
VOC Member
I have tried a thicker washer , ,and yes ,Not much thread left ,and just touches the cap
I may need to machine a bit out and thick gasket ,
Thanks Greg

Bill Thomas

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VOC Member
I am a bit late Greg , But seeing a photo of Steve Hamel's Bike,
I Wonder if you could cut 2 caps and weld together, So that you would have a longer / Deeper wider part ?
The only problem I see is the valve cap that is close to the bottom of the Oil Tank.
Good Luck, Bill.


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VOC Member
I would have thought that this is a problem only when using high-lift cams. I do not use the original valve locks because I use Gold Star springs. However, if the groove for the new automotive-style valve lock is cut a bit high on the stem, the spring will require a shim underneath. When setting the installed height of the spring to the correct pressure, the retainer will sit higher. This may cause the retainer to hit the cap.

The first way to attack the problem could be to use a lower retainer. The stock Vincent retainer is very deep and I have been able to shorten the retainer quite a bit to get more room.

DSCN0415 L (2).JPG

The spring on the left is a beehive spring, so it is a single spring that is shorter and stiffer. The Vincent spring is a double spring (a triple spring was used on the Lightning and Flashes). The spring ends up being compressed much further than the beehive spring, which is why it is taller in its free state. However, the "reach" of the stock retainer is very tall. I assume that this was done because the Factory did not want the longer spring to become coil-bound as it was set to the correct height.

I used a shim in addition to a gasket to keep the cap as tall as possible. Due to placing the lock groove a bit high on the exhaust, I needed a taller cap on the exhaust valve.

100_0415 L.jpg

I took an older cap that had a hole drilled in it and then used a hole saw to enlarge the hole. Still, I needed shims under the cap to get more clearance, but it became clear that I could simply cover the hole with a piece of aluminum welded to the top. Note: the retainer is not the beehive retainer I showed, but an RD Valve retainer. It is all trial and error to get the correct installation height with the lowest profile. I plan to switch to beehive springs on the next racing engine.

100_0416 L.jpg

I selected another aluminum gasket ( some sealant on both sides) and that is how it has run to this day.

Now, I always change the rake of the steering head on the Comets, so there is plenty of space between the UFM and the intake valve cap.

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