Weber Vacuum vs. Pertronix 1 SVDA" Distributor, 12 VOLT, Need to know if I can just tap the intake manifold? Options

[mturner7]

Hi Everyone, This vacuum connection to the weber carburetors has been talked about 100 times, but I need to address it again.

CAR/Engine:
1) Porsche 914-4: 1975 1.8L big bore build, dual IDF 40 Carbs

2) I have Weber 40 IDF 19 's with no vacuum port

3) I have a Pertronix 1 SVDA Distributor, 12 VOLT with electronic points

4) I have two sets of intake manifolds
- One set has a port already drilled and plugged see photo
- The other set does not have a hole/port

5) Since my new Pertronix 1 SVDA Distributor, 12 VOLT has the combination of centrifugal and vacuum advance installed.

6) Can I just remove the plugs in the intake manifold and add the vacuum line with a "T" back to the distributor?

7) That's the way it is connected in my 1974 Porsche 914-4 2.0L car, except the car has dual weber 44 IDF's with a vacuum port on the bottom of the carb itself.

8) Please help, I'm in the middle of my build and coming close to installing the carbs, intake's, and distributor.

p.s.: I have two sets of intake manifolds, the holes that connect to the carbs are different on the two sets.

- 48mm for the short ones
- 40mm for the long ones

The 48mm ones were on the engine with the weber 40 IDF's
The 40mm ones were on a car with Weber 44 IDF's

The 48mm ones have the port driller and tapped.

Will it matter which one i use>? 40mm hole or 48mm hole?

[bbrock]

You want the vacuum port for advance to be above the butterfly on the carb. That way it pulls vacuum as you open the throttle. Ports below the butterfly are for vacuum retard.