Vacuum gauge

[Puglet1]

I am trying to work out how to measure the vacuum in my manifold.

 I have removed the servo pipe adapter from the manifold and it has a very fine thread which measures about 9.3mm OD.

 I am looking for an adapter which will fit into the 6mm ID hose of my vacuum gauge.

Can anyone tell me what size adapter I should be looking for in BSP or BSF as I  haven’t got a clue about thread sizes.

 I am thinking about using an adapter like the ones shown in the photo.

 

Many thanks.
Pete.

[Morgana]

Without a thread gauge and/or a specification it's rather difficult to identify. Why don't you just put a tee in the servo hose and take the vacuum gauge off that? Are you looking to plumb it in permanently, or just as a tuning aid? What's the car and engine setup?

[Puglet1]

31 minutes ago, Morgana said:

Without a thread gauge and/or a specification it's rather difficult to identify. Why don't you just put a tee in the servo hose and take the vacuum gauge off that? Are you looking to plumb it in permanently, or just as a tuning aid? What's the car and engine setup?

The car is a Mk2 vitesse with a servo fitted. It’s just for a tuning aid so not permanent.

Thank you.

Pete.

[Morgana]

If it's been drilled for an aftermarket servo (I have no idea if the Vitesse came with one, but Canley's parts list suggests not, and other threads on here showing various servo installations support that surmise) then it could be almost anything. Around that major diameter you've measured it could be BSW, BSP(P or T), BSF, UNF etc. Without a thread gauge or plate to screw it into, or a helpful motor factors to test it for you then you're not going to have much luck tracking down the thread. Witness the hair-pulling I gave myself with the screw specifications on my carburettor...

If you just want to tune with the vacuum gauge, can you disconnect the brake servo (the car will be stationary) and just use a reducing hose adaptor between the servo hose size and the one on your vacuum gauge? My gauge was secondhand and came with lots of tee pieces and double-ended hosetail bits for connecting different diameters of hose. Fiddle for the highest vacuum, back off 1" then take off the gauge and hook the servo back up and take the car for a drive.