Need Help Identifying Thread Type / Size

I need help. I bought this manifold and neither the company I bought it from nor the manufacturer can tell me what size fitting I need for the threaded hole intended for the brake booster. They said 3/8" was too small so it may be 1/2" BSP or NPTF. Nothing I can find at the usual spots fits. Of course the big box stores don't carry British pipe thread.

Here's the hole. The closest I can get with my thread gauges is metric 1.5.

To what would be the outside of the threads on a fitting at the top of the hole measures just about 7/8 of an inch or about 22.4 MM

I cannot tell whether or not it's tapered but the inside measures .8155 in or 20.72 MM

Does this seem to be M22 x 1.5? 

What's it go on? 15/16 Witworth if it's for something old and British?

If you could tell us who the manufacturer is and the year/make/model/engine it is going on then perhaps someone here is familiar with it and can help.  
 

To determine if the hole is tapered see if you can find a socket that fits in the top of the hole but gets tight lower down.  

Is this for the Healey or the BMW? If Healey it is BSP, and Pegasus is your best bet if it is not available from Moths. Original BMC was a banjo and banjo bolt even for a hose.

This goes on the BMW. Mounts dual DCOEs to a BMW M10 engine.

I bought it from Eurocarb/Dellorto and it the only branding anywhere is on the hardware bag which is Webcon.

Doesn't one of the BSP/NPT match? Like 1/2" thread is the same?

Brotus7 said:

What's it go on? 15/16 Witworth if it's for something old and British?

Sir Joseph had some odd engineering thoughts on threads but, but I don't think his standard included pipe threads. I would imagine that is a tapered pipe thread, of some flavor. 

7/8 orb?

Maybe 7/8-20 thread?

Male plug

This is the stock 2002 part, p/n 34331102538. The sealing ring is 07119963355, which is listed as "A22X27-AL"; there is no listing for the thread that I can find. No idea if it will fit, but that's what I'd try first.

Edit: Photo suggests thread is not tapered.

In reply to 03Panther :

BSP, British Standard Pipe, has nothing to do with the Prince of Darkness, and there are both straight and tapered BSP threads. The Germans never had a tapered pipe standard. In fact there is not yet any Metric taper pipe thread standard...Give em time....

1.5mm is really close to 16tpi, not 20.

I wouldn't doubt that it's 22x1.5.

Hmm..

Summit lists a lot of AN adaptors... and when doing a general search for M22x1.5, also a GM transfer case plug.  https://www.summitracing.com/parts/ado-89059626#overview

In reply to 02Pilot :

Man, I never even considered that this would be made to accept a factory BMW fitting. That's definitely the bugger. I did order an M22 x 1.5 to AN6 fitting that will be here today and from the bit of information I have been able to dig up on that it seems to be M22... We'll see. 

Thanks everyone. 

In reply to TurnerX19 :

Joseph Lucas  was a few years younger than Sir Joseph Whitworth, and is only a prince in jokes. Not sure what the official designation of Sir means to the Britt's, but we have a couple ex-pats that would know. 
No one mentioned random electrical gremlins in a "thread" about "threads" 

Yes, there are many straight thread pipe fittings (usually sealed by an o-ring or washer) as well as tapered. Without having the part in hand, I thought I saw tapered. But NoTime and O2Pilot looked closer!

Witworth (officially started by a Joesph with a "Sir") thread standard is not related to BSP, or any other sealing type thread, was my only point. (It's definitely not 15/16 Withworth)

Sorry I confused some people, but in context of "threads", different "Joe's"

It is indeed M22 x 1.5

03Panther said:

In reply to TurnerX19 :

Joseph Lucas  was a few years younger than Sir Joseph Whitworth, and is only a prince in jokes. Not sure what the official designation of Sir means to the Britt's, but we have a couple ex-pats that would know. 
No one mentioned random electrical gremlins in a "thread" about "threads" 

Yes, there are many straight thread pipe fittings (usually sealed by an o-ring or washer) as well as tapered. Without having the part in hand, I thought I saw tapered. But NoTime and O2Pilot looked closer!

Witworth (officially started by a Joesph with a "Sir") thread standard is not related to BSP, or any other sealing type thread, was my only point. (It's definitely not 15/16 Withworth)

Sorry I confused some people, but in context of "threads", different "Joe's"

Sir means they have been knighted. 

A Knight of the Realm

In reply to wvumtnbkr :

That was my assumption, but was not positive. So, a Knighted Sir, would trump a Prince of Darkness (that wasn't really a prince?) 

They were both genius level in the mid 1800, despite the common jokes!

In reply to AxeHealey :

You put an oring on that?