RV8 vacuum canister screws - what thread?

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ratwing
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RV8 vacuum canister screws - what thread?

Post by ratwing »

I've dropped one and lost it - does anyone know what the screw thread is so I can get some more? (I only need one but a few spares might be a good idea for next time I lose one...)
I don't know if it makes a difference but it's from a 1972 p6.



ratwing
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Post by ratwing »

I tried a couple of Land Rover suppliers, it seems the screws aren't listed as spares...
I took the remaining screw to a nut & bolt supplier, unfortunately they couldn't match it. The thread pitch was a close match to 4BA at 0.66mm (I think that's what they said), mine measured 3.78mm diameter but 4BA is too small at 3.6mm so they suggested running a 4mm x 0.7mm tap through the holes and using matching metric screws.
I was a bit unsure about this but noted that there is room inside the distributor for nuts in case it all went horribly wrong so I wound the tap in and am happy to say it seems to have worked.

DaveEFI
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Post by DaveEFI »

Must admit to not knowing what you meant by the first post. :D

I presume it is the vacuum advance unit on the dizzy?

Old Lucas stuff was usually BA before going metric. But the other possibility into soft metal is UNC.

Thought I had some 3BA lying around to measure, but not. If UNC, might be the same as computer HD fixing bolts? Which are probably American Coarse but could be close enough to UNC.
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ratwing
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Post by ratwing »

Sorry, yes, the screws are for attaching the vac canister to the distributor, I should have said so in the first post.
You're probably right and they are 3BA although it seems odd that the guy in the shop said it wasn't.
3BA is 4.1mm diameter and 0.73mm pitch so that's probably why an M4 tap went through so easily.

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