Timing using vaccuum gauge?

I read a post that stated I should put a vaccuum gauge on my "Manifold Port", in order to adjust the timing and the idle. Does anyone have a better explanation of the where the "Manifold Port" is and possible a picture? I have a 66 Mustang with a 200ci 6cyl and a 1940 Holley carb.

Thanks,
Ed

Any connection/port providing full manifold vacuum. If nothing else, use the PCV port with a bit of adapting for hose size.

The right angle line coming out of the carb throat is to the vacuum advance on the distributor. That is carb port vacuum.

The brass block below it is the manifold vacuum port. It has the transmission modulator line coming out of the front. The other two ports are blocked. I use the small one for the vacuum gauge when I tune it. One day I may use the larger one for power brakes.

Ok, I see the connection. It is plugged on my car, because I have a manual tans. So, if I uderstand correctly. I remove the plug, connect the gauge and then start the car? What will happen if the gauge comes off the connection? Will the car shut down? What I mean is, I know that you need a tight connection to get an accurate reading, but if the gauge is not tight, will the car stop or will it back fire out the hole? I am not sure how tight my gauge will fit, so I want to make sure it is safe.

Thanks for the input!
Ed

Little hole, not much problem. Plug it back up. It'll be fine.

Go to the hardware or auto parts store and find a brass fitting with a hose barb that fits the hole. The hose won't come off if the hose barb is the right size for the gauge line.

I read somewhere we should be getting 15-22 in hg. That's about 7.5 to 11 psi. Is that what you usually get idle, ludwig?

Anything north of 18". That is your minimum. Turn whatever you are adjusting to the highest point that is more than 18: dizz, A/F mix, idle mix.

My 82 Cougar is pulling 20" at 2,200 feet iabove sea level. I was told only 17-18 is possible 2,000 ft above sea level.

You're good. I got just barely 18 on the first go round. I get like 18.5 now and I'm at 1300', the same as Iowa. When your manifold vacuum drops, you are losing fuel economy.

Cars in the the Mobil Economy Run way back when had a manifold vacuum gauge mounted on the dash above the speedo. They were supposed to keep the needle as steady as possible. Like 'drive with an egg under your foot'.

I remember some old luxury car that had a dial on the dashboard labeled "fuel economy". I think the extremes were 'outstanding' and 'p*ss poor'. At any rate, the needle would bury at the bottom when you floored it at an on ramp.