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Just cleaning up the threaded holes in my engine / gearbox unit and wanted to confirm / find the thread specifications for some of them:
Are the spark plug holes M14 1.25 ?
Is the temperature sender hole 5/8" UNF ?
What is the thread of the bypass hose pipe in the head ?
What is the thread of the oil pressure gauge feed hole ?
And finally what is the thread of the sump plug hole ?

Thanks very much
Paul.

L7MAD wrote:Just cleaning up the threaded holes in my engine / gearbox unit and wanted to confirm / find the thread specifications for some of them:
Are the spark plug holes M14 1.25 ? Yes
Is the temperature sender hole 5/8" UNF ? Yes
What is the thread of the bypass hose pipe in the head ? 5/8" UNF
What is the thread of the oil pressure gauge feed hole ? 1/8" NPT
And finally what is the thread of the sump plug hole ? 5/8" UNC

Thanks very much
Paul.

Hope that's some help

the thread in the cylinder head is 5/8 th UNS not UNF

rich@minispares.com wrote:the thread in the cylinder head is 5/8 th UNS not UNF

So, the same as the crankshaft threads?

Yes it's the same as the crankshaft thread, which is WF and not UNS. It's in the manuals.

Smiffy wrote:Yes it's the same as the crankshaft thread, which is WF and not UNS. It's in the manuals.

Smiffy, you are correct. That was passed on to me a few weeks ago and upon checking, they are not UNS. A college did say a few years back that he tracked it down as a British Small Arms Thread, but I've not (yet) been able to find a table on them.

It's a Whitworth Form Thread not the same as BSF.

Smiffy wrote:It's a Whitworth Form Thread not the same as BSF.

No, it's not BSF, that's right, but (and I know what the W/S Manual says) it's not whit either. Whit has a 55 degree included angle yet the thread on the flywheel bolts are 60 degrees. It maybe a British Small Arms thread or it could be 16-UN Thread type, but definitely not British Standard Fine.

Thanks guys, I knew this would be the correct place to ask!
What manual are you referring to? As I looked in the mechanical parts book and the BMC workshop manual but could not see anything, is there another one?
I assume the thread in the head you are referring to in the last posts is the bypass pipe thread and not the temperature sender one?
Also is there a close match parallel thread to 1/8" NPT that I could re tap the oil pressure hole to fit a banjo bolt/fitting?
Thank again.
Paul.

the temp sender one is 5/8 unf, same as the servo fitting

This is from the factory manual AKD 4935



As you can see, it's only a mention of the crank thread (which is the same both ends by the way!).

The Oil Sender Thread is tapered for a reason I wouldn't recommend changing it to anything else. The correct tap should be easy to come by and not at all dear.

rich@minispares.com wrote:the thread in the cylinder head is 5/8 th UNS not UNF

Maybe a correction - somewhere - is in order?

https://www.minispares.com/product/Clas ... o%20search

I seem to recall that's where I originally found that info and that's what i have been fitting.