The V8 Owners Forum -

Yes 1 is described by Chris - in my 3.5 it goes to the heater tank of the radiator - it bleeds air out of the cooling system.

On my engine (3.5 in a FC 101) Number 2 is the vacuum port for the brakes and Number 3 is the vacuum port for the center diff lock. These are manifold vacuum so are interchangeable so work as Chris describes.

Ported vacuum for things like distributor etc comes from outlets in the the carb base.

Thanks Garry

I have had a manifold in the past where that little bleed pipe was rusted completely solid, so I didn't connect it! Not very advisable.

Yeah as Garry says, distributor vac comes from the carb. This is because it comes from right by the throttle plate, and is more subtle than just manifold vacuum.

Chris.