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Allchin valve chest

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Dougie Swan15/05/2022 11:55:50
235 forum posts
53 photos

Calling all allchin builders

I have reached the stage of machining the valve chest on my engine and I have some questions I hope you can help with

On the drawings there are 5 holes drilled through the cylinder base into the bottom of the valve chest from underneath, what do these do

Same for the 3 5ba csk holes and one of the holes appears to be drilled through the valve stem but there is a lack of hidden view of the end elevation on my drawings

Any help will be greatly appreciated

Thanks

Dougie

JasonB15/05/2022 13:09:10
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22749 forum posts
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Not made it but the 5 holes are for screws to permanently hold the chest vertically down.

chest 1.jpg

The 3 CSK holes permanently hold the chest horizontally.

Looks like it is a "B" hole which is a blind stud hole that is near the valve stem not the through "C" countersunk hole

chest 2.jpg

The chest would not have been a separate part on the original but doing it separately makes it easier for us to machine the ports and port face.

Edited By JasonB on 15/05/2022 13:10:42

Zan15/05/2022 13:12:15
312 forum posts
20 photos

I believe the original had cylinder and chest cast as a single unit. So these are 5x6ba gunmetal r head fixings to hold the chest down.

there is a clear section in the centre of sheet 6

the view  of the chest bottom left on the sheet shows they clear the spindle. 6 holes”a” to fix to cylinder etc

 

 

 

edit. Typo

Edited By Zan on 15/05/2022 13:13:51

Dougie Swan15/05/2022 13:33:20
235 forum posts
53 photos

Thanks guys

Jason, your drawings have way more detail than my set

The view of the cylinder cross section doesn't appear anywhere on mine

Just like before you sent me details of the steering bracket that is missing from mine, who did your drawings

Thanks

Dougie

Zan16/05/2022 14:36:46
312 forum posts
20 photos

My drawings are hidden away in the loft where they have sat since 1995 when it was put on hold! I looked in the book

Dougie Swan24/05/2022 14:46:15
235 forum posts
53 photos

Thanks for the replies

But I now have another question

When fixing the valve chest to the cylinder block what did you use for a sealant, I'm thinking of silicon, anybody got any suggestions

Thanks

Dougie

JasonB24/05/2022 14:48:53
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22749 forum posts
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I've used the liquid gasket from Halfords on several engines which is a form of silicon.

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