Technical Inlet manifold pre-drilled hole

[Ucof]

My vacuum gauge arrived today, it looks lovely and shiney.

However, in the instructions, it says:

The vacuum guage must be connected to the inlet manifold of the engine which on many vehicles has one or more tapped holes, blanked by means of a screw plug. To install the gauge into such a vehicle simply remove the plug and screw the brass adaptor supplied into the hole ensuring a 'gas-tight' fit.

If your vehicle does not already have pre-tapped holes, then the manifold will have to be drilled and tapped to accommodate the adaptor. The thread size of the one supplied is 1/2" - 27TPI

Now, does my inlet manifold have one of these holes by default, or will I need to drill one?
I've had a quick look and the only nut I could find, turned out to be just a clamp for what looks like a holding bracket for something. Wasn't connected and I don't have any clue what is supposed to connect to it.

(I'm probably going to get the garage to drill it and possibly fit it too- damn my lack of driveway and time )

 

[rawill]

Tis it all true!!

I think you have a fire engine, so not sure where the points are for plugging it into. But, If it was me I would get a 'T' fitting and come off an already existing vac point, like on the brake vac booster or where it goes to the vac diaphragm of the distributor.

But then again it would not be too hard to drill another hole in the manifold and tap it out, if you had the bits. But if you do, be careful with the drilling not to drop drilling swarf into the manifold. Go slowly with a battery drill, when you get close to braking through blow all the swarf away and coat the hole and drill with grease to pick the bits.

 

[Ucof]

Oddly enough:

It is recommended that the manifold be removed for such drilling so as to prevent swarf (metal particles) entering, wich would then be drawn into the combustion chambers possibly causing serious damage. The adaptor should be positioned at a point in the manifold as near to the centre and top as the carburettor etc will allow.

and also..

The tubing to the vacuum gauge must not be connected into distributor vacuum lines or vacuum assisted brake lines.

Thanks for trying though squire!

 

[Chas Uno]

You might be interested to note that the standard fit 'econometer' (a vacuum gauge under another name) in mk1 45S and 60S models took its vacuum from the brake servo boost hose

 

[Ucof]

So would both inlet manifolds be the same or are they different due to different engine sizes?

Would I even have a brake servo on my Fire engine?
Haynes manual leads me to think that only 55s, 60s and Turbos have brake servos.

 

[Louie Bee]

I just had a look at my spare 999cc engine that lives on the garage floor and found no spare tapping. there may be one on the throttle body but I can't be sure as I can't put my hands on the spare.

I would suggest t’ing into the vac advance for the dizzy ahead of brake line drilling into the manifold which has a waterway for coolant to also tap into the dizzy line is probs the correct thickness for the T piece.

only ancient Unos had no servo . even my 1986 903cc Formula Uno had a one.

 

[Ucof]

Ok, I'll have a go at the vacuum advance pipe, as close to the carb as possible.
The gauge came with a t pipe thankfully.

I wonder why the instructions said not to use the brake or dizzy vacuum pipe though....

 

[rawill]

You might be interested to note that the standard fit 'econometer' (a vacuum gauge under another name) in mk1 45S and 60S models took its vacuum from the brake servo boost hose

That is why I posted my comment. The econ gauge comes of the brake booster pipe on my 60s.

 

[Chas Uno]

That is why I posted my comment. The econ gauge comes of the brake booster pipe on my 60s.

It comes off my 45S brake booster pipe too