Factory vacuum gauge

[BROWN 70]

Hi guys, was just looking at the tach thread and i wouldn't want to cover up my vacuum gauge. how many of you have a vacuum gauge there? 70 gmc custom. BROWN 70

[HO455]

I've never seen one like that. Cool stuff!

[jocko]

That's a mid-60's Pontiac vac gauge. There were no factory vac gauges in 67-72 in Series 10-30 trucks. Med duty had them (a different, smaller one than that), and many folks retrofit them into the unused gauge opening to the right of the column (where the Med Duty's had them).

[BROWN 70]

I bought the truck in 1980 and I got it from the original owner. he was a farmer and pulled a horse trailer with it. everything on the truck was numbers matching when I bought it. I don't think he put that gauge in. it has a grommet in the fire wall were it passes through to the pass side vacuum port on my q-jet. I met the owner of a 67-72 parts shop and he said he had seen one or two others like mine. one thing I,ve learned in this hobby is there are exceptions to the rule. I use mine a lot for mpg, and how the engine is running. have a great day, BROWN 70

['68OrangeSunshine]

It's a nice set up, but not factory. Not in the Tach hole. Is it listed on the SPID? Maybe a dealer add-on, but why a Pontiac gauge? Pontiac dealer? Could be, since it's a GMC.
I run an aftermarket [MoonEyes] Vacuum gauge in a shinscraper mount along with mech water temp, and mech oil pressure gauges. I have the Standard [idiot light] dash with 3 hole, not the 7-hole Deluxe.
Love my Vacuum gauge. Good on long trips for getting cruise throttle right. Saved the day a couple of times when valve springs broke and I could read on the dash that I had valve problems. Great for tuning up the carb. When I look at the instruments and see 750 RPM, 180* water temp, 40 PSI oil pressure and 17" Hg, I know my engine's running right.
An under-appreciated instrument, the Manifold Vacuum, IMHO.

[HO455]

Looks like the only answer is to have a full teardown! Pontiac wasn't the only one with vacuum guages. I have a no name one that I pulled off the console of a seriously rusted two door 62-64 Impala back in the mid eighties. I would have to pull it down from the attic to see if it is an exact match. It was the only good part left on the car.

[weq92f]

Originally Posted by '68OrangeSunshine

An under-appreciated instrument, the Manifold Vacuum

Agreed and well stated

-klb

['68OrangeSunshine]

Originally Posted by weq92f

Agreed and well stated

-klb

Thank you, Sir. You're a gentleman and a scholar.

[davepl]

Originally Posted by BROWN 70

everything on the truck was numbers matching when I bought it. I don't think he put that gauge in.

It's a fun gauge, and an intriguing way to mount it, but someone added it, and not GM. Probably in the mid-70s during the energy crisis.

If you've had it since 1980 though and it's been there, it's original to you, so I wouldn't get rid of it unless you REALLY wanted a factory tach.

[burb71]

I dont think its factory installed.
As jocko said the medium duty trucks C/40, C/50 & C/60 basically used the same dash as our light duty trucks, and they did have an optional vac gauge it filled in the blank spot on the lower left in the gauge cluster.
The blank spot where you have the vac gauge is for the optional Tach.
We have also seen guys put after market tachs and clocks in that spot.
Another way to know is there is no reference to a vac gauge in the owners manual

[jocko]

Good point HO455, Pontiac was not the only GM make to use these - but, they were all GM. The little faceplate that hid the needle base usually carried the Pontiac spear or the Chev bow tie on it. Many were console mounted mid-60's in a chrome cup. Here's the one I stuck in my 66 dash a while back. It's a great gauge, adds a little color to an empty spot and is semi-useful. 2nd pic is one of about 8-10 on ebay right now from $100-$400 ish. Just google search Pontiac Vacuum Gauge and you'll find a slew of them.