Vaccume Guages?

[Nunyas]

So, I was looking around on eBay and found a vacuum guage has been placed up for bid. Recalling from my childhood, my parents had recieved a vacuum guage as a gift for their 'B. I've never fully understood the purpose of these devices being installed into a car. 'Boost' guages I understand having when the car is equipped with a super-charger or turbo-charger... but a vacuum guage?

Could anyone care to explain why someone would want to have one of these (vacuum guage) installed in their cars?

 

[aerog]

I've never seen one. Where are they monitoring vacuum pressure from? Straight to the crankcase, or the brake-servo line, or what? I can see the interest in a manifold pressure gauge (which I've seen in an MG-TD) but not raw vacuum pressure.

 

[Steve_S]

They measure vacuum advance which is related directly to timing. I'm no expert, but that's what I've been told. The really sad thing is that I have one in my GT and I don't even know how it's hooked up! In my own defense I've only had the car a month. /ubbthreads/images/graemlins/rolleyes.gif

Nunyas, feel free to swing by and check mine out if you're curious. I'm only 20 minutes from Burbank.

 

[Dave Russell]

In my experience, vacuum gages connected directly to manifold vacuum, sometimes have value as a temporary diagnostic tool. The only time that I have gotten any real info from one was when I was trying to determine just where Holley carb power valves were opening in relation to various driving conditions.

I HAVE found a combination vacuum/pressure gage to be of some use on a turbocharged engine. Mostly for monitoring an adjustable boost control & setting engine management adjustments in relation to road loads.

On normally aspirated engines, I think that permanently mounted gages have very little benefit. Especially once the novelty has worn off. I would suggest getting a low cost diagnostic gage & temporarily mounting it for a trial before commiting to a permanent installation.
D

 

[Bugeye58]

I seem to remember vacuum gauges being installed back in the fuel crunch days of the late 70's, as "Economy Gauges."
The lower the vacuum reading, the greater the throttle opening, and consequent lower fuel economy. Well, " <u>DUH</u> "!!
Totally pointless for a permanent installation, in my opinion.
Jeff

 

[Steve_S]

I don't use mine for any practical purpose, but it's one more thing that moves around and makes passengers go "Ooooh! What's that?" /ubbthreads/images/graemlins/smile.gif

 

[Guinn]

The only real value I remember for the vacuum guage was that it would indicate a sticking intake valve by dipping each time that valve was slow to close. Some said that it would also indicate engine wear if you kept records. A lower - or was it a higher - reading after a few thousand miles could indicate wear. Had one on my Datsun PU for a few years, then threw it out. And yes, it does connect to the intake manifold. I had a "spare" 1/4 pipe entry to the manifold and just removed the plug and put in a tubing adapter.

Guinn

 

[piman]

Hello all,
vacuum gauges, which are little used these days, are capable of diagnosing a vast range of engine maladies from ignition settings to compression issues, if you have gained the experience. I use one from time to time as my Triumph has a mechanical fuel injection system that relies on correct engine vacuum to function correctly.
The accessory type which you install in the car was sold as an economy aid, and you could be surprised at how much throttle you may be using unintentionally.
Personally mine is intentional.

Alec