Question on installing factory vacuum gauge

[Rich69shortfleet]

I just bought a factory tach and vacuum gauge conversion for my 69 C10 instrument cluster. Connecting the tach is pretty straightforward, but I'm confused about the vacauum gauge. The gauge does not come with any fittings but has a long threaded nut on the fitting on the back of the gauge which I'm assuming helps hold the gauge to the cluster. Anyway, I assumed there would be fittings along with it to connect a vacuum line hose from the gauge to the engine. There was nothing and there were no instructions.

I don't want to damage my new gauge so I'm asking. Is the way to connect it to find a screw on fitting for the back of the gauge with a barbed nipple that can connect to a vacuum hose that can then be routed to the engine's manifold vacuum? I can't imagine it would be any more complex, but I wanted to make sure. Not sure why such a needed fitting wasn't supplied.

['68OrangeSunshine]

You don't want to use rubber hose. Use 1/8'' copper tubing. That's what it's designed for. Any auto parts store will have compression fittings and tubing.

[Rich69shortfleet]

Originally Posted by '68OrangeSunshine

You don't want to use rubber hose. Use 1/8'' copper tubing. That's what it's designed for. Any auto parts store will have compression fittings and tubing.

Where at the engine can I connect a copper line? I have plenty of fittings and tubing, just nowhere to connect it at the engine end.

['68OrangeSunshine]

Usually on the intake manifold.

[cdowns]

rubber vacumme line is morethan acceptable no need for copper tubing

just so you know that your truck never had one and none was optional as accessory it was only available on bigrig trucksthat is just a monkey see monkey do adaption

[Rich69shortfleet]

Originally Posted by '68OrangeSunshine

Usually on the intake manifold.

Well duh, but there are no acceptable fittings at the manifold. Aftermarket intake and a Q-Jet. I'll just look for an available fitting on the base of the carb.

[Rich69shortfleet]

Originally Posted by cdowns

rubber vacumme line is morethan acceptable no need for copper tubing

just so you know that your truck never had one and none was optional as accessory it was only available on bigrig trucksthat is just a monkey see monkey do adaption

Yeah, no biggie, but they are helpful in trying to attain higher fuel mileage. That empty hole in the cluster always bugged me anyway!

My truck never even had gagues to begin with, I installed a set of gauges and associated harness out of a 71 Cheyenne, has always worked great.

['68OrangeSunshine]

Originally Posted by Rich69shortfleet

Well duh, but there are no acceptable fittings at the manifold. Aftermarket intake and a Q-Jet. I'll just look for an available fitting on the base of the carb.

Yeah, sorry. You never stated engine type, displacement or year. Mine's on an L6 292 w/ Offy aftermarket intake. The Offy has multiple places with plugged fittings for extra stuff. It's 1/4'' NPT, I think. I also have a Weiand intake on a 350 V8 in a '71 GMC, and it has a 1/2'' input [in the #8 cyl plenum] I used to use for the power brake diaphragm. Because of a lean-out condition on the #8 cylinder causing misfires - I swapped the P/S feed to the back of the carb. A Vacuum gauge would * NOT draw enough A/F mixture to interfere. Whose ''aftermarket intake'' did you buy?
[*EDIT]

[Rich69shortfleet]

Originally Posted by '68OrangeSunshine

Whose ''aftermarket intake'' did you buy?

I should have specified what engine, but I really was after generic info at the start. I thought the gauge would just have a hose nipple on the back so I was a bit confused when I pulled it out of the box. Makes sense that Chevy connected it via a hard line though.

It is a SB400, I have an Edelbrock Performer Q-Jet manifold. Noticeable improvement from the original GM cast iron manifold. I have power brakes so there is probably an outlet on the back runner, but I think I'd rather the vacuum gauge get its own dedicated line. I think there is an unused port on the carb base other than the one used for the vacuum advance. I doubt it matters, but never hurts to give each their own source. I like the idea of using that plastic oil pressure line for a vacuum line. Easy to run and fairly durable. I never use the stuff for oil pressure lines so I have a few rolls of it lying around unused from previous oil pressure gauge installs. I found some compression fittings that will attach either plastic or copper lines to the gauge, now I just need to determine where on the engine I can get vacuum and determine how to connect this small line to a vacuum source.

['68OrangeSunshine]

I still wouldn't use plastic/nylon lines in the engine bay. The copper line is bomb-proof. The softer lines are susceptable to high heat, heavy vibrations and operate in a petroleum/hydrocarbon-induced atmosphere. Recipe for failure.
If your oil pressure line breaks, you get hot oil squirting all over the place. A vacuum line break would definitely give you a vacuum leak.
In my environment, Tuscon with Summer coming on, it's unthinkable.

I meant to say a vacuum gauge in the #8 runner would not draw enough to interfere with the A/F Mixture.

[rusty knuckles 5]

mine has a special "t" in the vacume line that goes to the power brake booster it came with a after market vacume guage kit, hope this helps

[Coley]

Heavier wall rubber tubing is just fine, definitely a very good practical choice.
I've run my factory vacuum gauge on it for years and years and years...no fails, nothing wrong whatsoever.
The rubber tubing will forgive engine movement, torqueing, etc and are more than acceptable for use in this purpose.
As for points to tee into to pick up the vacuum...I installed a different fitting at the back of the (original) manifold and it had an extra connection point....worked out great.

All Good
Coley

[Ironangel]

http://www.frsport.com/1-16---NPT-to...FQ2QaQodeu0C_A Your Quadrajet should have the barbs and ports necessary for the vacuum advance and brake booster. If you need a dedicated port for the transmission here's a few options. http://www.ebay.com/bhp/vacuum-intake-fitting As long as you use a quality reinforced rubber "vacuum line" from a barb on the back of the manifold to the gauge your good to go for years of leak free use. You can also use a braided stainless line if looks and durability is important.