Best source for in cabin vacuum gauge

[thebigredrocker]

On a stock 71 FJ40. Aisan carb, canadian carb with a ported base. Is there a prefered spot to plumb a vacuum gauge? Intake manifold, choke pull-off line or dizzy line?

Does it even matter?

Thanks

 

[shawnfj40]

The most accurate would be the main plenum of the intake manifold.

 

[65swb45]

If you lack a 10mm port on the topside of the intake, the booster line is next best. That said, the 10/69-9/70 carbs offered a manifold vacuum port in the fuel bowl of the carb. It utilizes the hollow screw that comes up through the throttle body to secure the fuel bowl. Some people would argue that it is not true manifold vacuum at that point, but I consider it good enough for all my needs.

Best

Mark

www.marksoffroad.net

 

[FF LC FREAK]

I did as Mark suggests. I teed into the line to the brake booster. Works great.

 

[Curt]

Booster works well for me to. Easy location to work on as well.

 

[lc69hunter]

I am running a Holley. There is a vacuum port coming off the base of the carb on the firewall side. I run my gauge off it.

 

[JohnnyC]

I used the port on the top of the intake

What are you going to use for a gauge? I just have a vac tester on magnet lol works well

May want to go nonPO of some sort

 

[thebigredrocker]

Thanks for the reply's fellas. I do have two nipples on my intake manifold. Vacuum transfer case hose and booster hose.

@65swb45
Is this the bowl mounted port you mentioned as acceptible?

 

[thebigredrocker]

@JohnnyC I like your Vac gauge solution. I bought a coulumn mount pod and a small AutoMeter gauge. Trying to be a good PO on my 71.

 

[65swb45]

Thanks for the reply's fellas. I do have two nipples on my intake manifold. Vacuum transfer case hose and booster hose.

@65swb45
Is this the bowl mounted port you mentioned as acceptible? View attachment 1368014 I was curious so I pulled my carb apart. I learned that this bowl mounted port draws vacuum from a tiny hole below the primary throttle plate.
View attachment 1368018
View attachment 1368019

That's the one.

 

[thebigredrocker]

Here’s that goofy port @Casey E

 

[JohnJL]

OK, I'll bite...what does this do?

 

[71FJ40]

Came off the intake on my trail truck
PO had cut a hole for the radio.... so that worked perfect
Gauge from Summit Racing

 

[71FJ40]

VDO Cockpit Series Analog Gauges 150042

VDO Cockpit Series Analog Gauges 150042

AutoMeter Sport-Comp Analog Gauges 3484

Autogage Analog Gauges 2337

I recommend using high quality silicone tubing to run to the gauge. You dont want to introduce any vacuum leaks

 

[thebigredrocker]

@JohnJL

The PO put those there. Guessing maybe he was a pilot or at least around airplanes. If he was an airplane mechanic, he definately didn’t pass any knowledge to his offspring

Here’s the best explanation I’ve gotten so far:

My guess is that they were part of the PO's whimsical nature... My first '74 spent time as an airplane tug for his company at the San Antonio Airport (He said it pulled a DC9 once). It still has "fasten seat belt while seated" and "life vest in seat pocket" stickers on both sides of the dash.