Vaccum port on IDFs. (maybe silly question).

VW_Factor · Post by **VW_Factor** » Sun May 14, 2006 8:46 am

Would the port for vaccum be located at number 36 in this diagram?

http://www.webernorthamerica.com/pdffiles/40IDF70.pdf

500LbGorilla · Post by **500LbGorilla** » Sun May 14, 2006 9:06 am

That's not a clear picture. The port will be here (ignore the screwdriver):

VW_Factor · Post by **VW_Factor** » Sun May 14, 2006 9:21 am

In the diagram, (or in your picture) I thought it was the small short plug directly "under" the longer one you have circled. Its installed into the throttle plate.

Anyway, the longer one is where I should install a tube for vaccum?

500LbGorilla · Post by **500LbGorilla** » Sun May 14, 2006 9:42 am

The other one is a blanking screw for a port that does not work for vacuum advance. it will give a signal all the time.

If you're saying there is no fitting for a line in the casting, it would be installed at that location, yes.

The port pilot is very small. If you want to drill it out, you need to be very careful and find out what the right size hole is. You'll get one chance.

If you DO have the tube fitted there and a plug or a screw over it, just take the plug or screw out, and connect the line to your vacuum advance. Make sure the line makes a run up a distance, and back down, to keep fuel from trying to leak into the line and into the vacuum can on your distributor.

VW_Factor · Post by **VW_Factor** » Sun May 14, 2006 9:45 am

So, under the proper screw, it is not a full hole into the throat of the carb, so I will need to drill it out? Then find a tube that fits snuggly into the hole that is drilled, and be golden?

I should do both carbs, and Tee them into 1 for the vaccum in this operation correct? I understand that 1 carb may not carry enough vaccum for signal.

500LbGorilla · Post by **500LbGorilla** » Sun May 14, 2006 9:53 am

Like I said, if you have the tube, and the screw is in it, or it has a plug on it (rubber cap), then it's there and functional, and you just need to run the line to your distributor. T fitting is a better way, yes. There should be one on the same location on each carb. One on #1, and one on #4.

Here is how I did mine.

VW_Factor · Post by **VW_Factor** » Sun May 14, 2006 9:58 am

Thank you very much for the pics and information. I do have those screws on the carbs, so I will be looking into that more closely this afternoon. I will hopefully be able to pick up an SVDA dizzy sometime this next week as well.

500LbGorilla · Post by **500LbGorilla** » Sun May 14, 2006 10:01 am

THe more metal line you can run the better, IMO, too. The rubber line over a decent length is going to want to partially collapse, which temporarily will take some of the vaccum signal to do that work, but eventually will reach equilibium at the same vacuum as long as the line does not totally occlude.

Good luck!