hello, i have searched 28 pages of the forum and can't see anything on how to hook up vacuum advance on webers. I have a 45DCOE13 and about to mount to my car but don't know where to hook up the advance i have searched google and the only thing i have found is a "Vacuum take-off cover", is this what i'm looking for, or is it taken from the inlet manifold (don't get the manifold til tomorrow so)....

i don't mean to make you sound idiotic, but is there a little valve off the bottom of the weber that just hooks up to the vacuum advance tube. on my 32 36 there's one. maybe take pics of carby??

RainWarriorDregs - This is for a sidedraft weber not downdraft, bit different. :)

 

Have a look at this thread...

http://www.rollaclub.com/board/?showtopic=19073#

 

You can see in the pic that Mark has taken a small vacuum line tapped of the main brake boost vacuum line.

Your manifold should have a boss in it that can be drilled and tapped to put a fitting in, if you're not already running a brake vacuum hose.

 

Mine does and it's just got a bolt threaded in there to block it off, although that is a twin sidedraft manifold.

thanks for your replies guys, got the manifold today and it has the output for the brake boost, but my leading hand was saying something about not putting them together or something. Something about the different sizes, but from that other thread he just uses a t-piece that has both sizes on it...

Shouldn't make any real difference, all you need is a vacuum signal.

 

The only issue I could forsee is the slightest, and I mean slightest lag in the vacuum signal when you have the two together. That'd be because the additional volume of the booster.

 

But really I wouldn't have thought you'd even notice that.

I have since changed this setup and I am currently running no vacuum advance.

how did you set it up with no vacuum advance, just advanced the timing a bit or?

Shouldn't make any real difference, all you need is a vacuum signal.

 

The only issue I could forsee is the slightest, and I mean slightest lag in the vacuum signal when you have the two together. That'd be because the additional volume of the booster.

 

But really I wouldn't have thought you'd even notice that.

 

...and you'd only get that after actually braking when the motor has to put vacuum back into the booster.

 

The vacuum advance only pulls about 6* of timing depending on exactly what dizzy it is, so its not hard to do without it.

Vacuum advance gives you better fuel economy on the cruise. Under high load conditions there is no vacuum.

 

You could always tap each manifold runner and make a "vacuum manifold".

 

Manifold vacuum is different to ported vacuum (source from the carb near the throttle plate). With manifold vacuum you get full vacuum advance at idle, which can really help smooth out the idle of a big cam.