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MG Midget and Sprite Technical - Vacuum gauge

Hi all,
Found a vacuum gauge ( well its flagged as an economy gauge) & the take off plate for the carb whilst rooting about in my spares box.
Happy enough about installing it ( I've got it - I'll use it!)but which is the best carb to install it to , or does it not matter?
Cheers colin
colin frowen

How does the take off plate fit ?

Is it sandwiched between the carb and the manifold ?

If so - doesn't that put the carbs out of line so the linkages don't work ?

Malc
Malc Gilliver

Hi Colin,
Prop will be along soon, saying that you cannot fit just one vacuum gauge if you have two carbs. You will need to buy another gauge and fit one on each carb!



Sorry, that was no help at all.
I'll get me coat...

Dave
Dave Brown

And one for each of the inlet runners too ;-)

Malcolm
M Le Chevalier

My vacuum gauge is take off inlet manifold and seems to work well.
There was a tapped hole with a blanking screw and leather washer already there so just had to replace the screw with a small spigot.
I guessing that the manifold isn't a standard factory fit.

Ian
I Ball

I like the way you are thinking, Malcolm.

To get better information from the gauges, one would need an external air pressure gauge for comparison too.

Dave
Dave Brown


I have one fitted, as I like a lot of instruments, its a waste of time however, as if you drive along looking at it, you are going to hit something and the scale is no good for tuning, I have a proper vacuum gauge for that.
Take off is from the centre of the manifold.

Dave
Dave Barrow

Here is a picture of it fitted

Dave

Dave Barrow

Dave ...im here,

your almost correct... you need 2 vac gauages and to 2 electric vac switch splitters ... so in reality, you have 4 vac gauges at the press of a button....

Hahah... well okay, perhaps thats just me...I wish I could figure out how to make 2 gauges into 4 for a total of 8 gauges...messed up I know

Fun aside and seriously speaking... but all true above

If your installing on a carb, then id do the rear carb at the same location as the frint carb for the dissy vac port... I think it would balance it out but probably only neglegiable

The best place I like fir getting vacume to read is the intake manifold at the pvc location that big nut right on the top of the intake manifold almost in the center

The next best spot would be on top of the valve cover

For a 2nd vac gauge I like the vac hose that goes into the timing chain cover... but that vac gauge needs to be very sensitive as it only draws about 1 - 2 psi (sorry my gauge is scaled in psi) which is minimal for an auto vac gauge to register

I love vacume and positive pressure and the various effects it has... its just fun to think about even ifit serves no purpose in day to day driving

Good luck

Prop
Prop and the Blackhole Midget

They also make quick release connectors... I get mine at a large 18 wheeler repair shop...the make the attaching end in both male and female and several various thread sizes

Ive also noticed that lowels and home depot carry some really cheap doddgy looking ones in plumbing

They also make them in various hose sizes for the little tinny size hose upto the 3/8inch

A bit pricy, but I think worth the cost for looks, reliability, and ease of use and install

Prop
Prop and the Blackhole Midget

The one thing I would add Prop is that by its very nature, vacuum is lighter than air (it's less dense than air at standard pressure) and so the connection should be at the TOP of the manifold. Fortunately most manifolds are predrilled that way, which supports my little known theory!
Pressure would be measured from underneath.
It's all a bit like hot water rises and cold drops.
Graeme W

I think I read that theory in the Handbook
Graeme W

I agree graeme,

What I have a hard time comprehinding, is what exactly is vacume....its not really air, as there is no air in a vacume...so its a neg pressure

Whats interesting, try buying a gauge scaled in bars ...its not easy to find

Its all marketing to a dumbed down socity

Prop
Prop and the Blackhole Midget

Prop - avoid bars!
Accessory shops are more likely to have stock.
Graeme W

Hahaha... nature may abhore a vacume, but she is my kind of gal

Prop
Prop and the Blackhole Midget

This thread was discussed between 04/06/2014 and 06/06/2014

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