OT car vacuum gauge fitting

Presumably a 'T' piece in any of the vacuum pipes would do, try your nearest tropical fish selling pet shop, and cut the adaptor off the neo tube from the gauge.

================================== If the original was the 'drill and tap' type then you might be able to use a grease nipple; some have a bit of an extended stem (probably used on prop shafts) to give better access. You might even be able to use a brake bleed nipple.

Cic.

Most of them were drill and tap pipes, BUT there was a restrictor in the adapter with only a pinhole to let the vacuum through.

================================== Grease nipples usually have a restrictor so this might serve as the required restrictor for the vacuum, but it might be necessary to drill out with a fine drill. It really depends on how keen the OP is to get his gauge installed and working. I don't think I would bother, although I fitted a few many years ago.

Cic.

I'm sure you can buy adapators and T pieces from any motorsport parts supplier. You can either T in to the distributor vacuum advance pipe, the brake servo pipe or drill and tap a separate fitting into the manifold. It'll need a damping restriction though to stop the gauge pulsing.

What do you want to measure? The "diagnostic" function of the old RedeX gauges used an adaptor with a larg(ish) hole through it, so that a sticking valve and the need for an imminent decoke would cause the needle to flutter.

A "Leadfoot gauge" that indicates the averaged manifold vacuum with a stable reading (and is thus an indicator for fuel consumption) needs a much smaller hole in the adapter.

Both of these holes need to be appreciably smaller than the connecting pipe bore. Don't plumb this in with the same skinny gauge of hose you'd use for an oil pressure gauge.

As you know already how far you've shoved your hoof down and decoking is something for the history books, along with soft valvesprings, then I really wouldn't bother - unless it's a period classic car.

Whether or not it's a direct-reading vacuum guage or not I don't know, but my motor has an instantaneous MPG dial. PITA, especially when you see the mpg drop to 5 or less when you hoof it!

Not sure it has much value in a fuel injection car anyway..

You can drill the inlet manifold and cobble up a pipe to it with car body filler, and slap the tube over that.

thanks all - interesting options there. There is abs. no good reason for me to do this other than to see the gauge needle 'propellering' to and fro again :-). I have long since lost the pamphlet which diagnosed gauge to fault finding - but doesn't matter now. Someone mentioned pulsing of the indicator - yes. This Red X one has a brass thumbscrew-type clamp which can be adjusted to damp-out those fluctuations. From distant memory I recall reading it as an "accelerator position indicator" ho ho.

It has exactly the same value for injection as it did for a carburettor engine with well-behaved carburation (i.e. not an SU with no damper oil)

Well has it? in a carburettor car the manifold pressure directly controls fuel flow rates.

In an injection car thats done by the air flow meter, plus a lot of other gubbins.

I am not so sure that airflow is always proportional to manifold vacuum..it certainly ain't in a turbo car..it's the other way round!

And it certainly ain't in a diesel, turbo or otherwise. There IS no throttle. Only a variable fuel injection system.

It may not _control_ it so directly in an injected car, but the proportional relationship still holds -- at least as well as it needs to for a gauge that's barely as precise as traffic-light colours at best.

Well there is that I suppose..

I could always tell anyway by the roar of the air going in to the twin SU's via the K&N pancake filters..

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember The Natural Philosopher saying something like:

First time I fitted one of those gauges I was quite impressed by how much I could back off the throttle and still maintain the progress.

And on ShiteOldJags you could tell by the rate the fuel gauge dropped as you hoofed it.

In message , Grimly Curmudgeon writes

which reminds me - I saw an Interceptor being what I would call hoofed today - he was prolly just being light on the accelerator really

You can't tell a damned thing by the air velocity into an SU (think about it)

Must have been a brake failure and it was pointing downhill.