3x2 vacuum issues

I have searched here and on a search engine. I have an edelbrock 3x2 intake and I'm using the speedway kit with the bases that eliminate the vacuum ports on the front and rear carbs. I have the center carb hooked up to the distributor for the vacuum advance. But I need another vacuum port for the th350 transmission and there isn't one.

What you guys recommend? I was thinking of tapping one of the intake runners and putting a port there.

Thanks in advance for any help

 

Tap directly into the plenum not a runner.

 

A tee fitting

 

wouldn't a tee fitting mess with the vacuum advance?

 

Would you recommend of the primary, or one of the secondaries?

 

If there isn't already a fitting behind the last carb then put one there so it isn't easily seen, but not in the runner.

Sent from my DROID device using the TJJ mobile app

 

Unlike a vacuum wiper or PCV valve there is no air movement to speak of so it doesn't matter where it is hooked up. It just moves a diaphragm a short distance.

No, teeing them together will not affect the advance or the trans.

 

What 31Vicky and tommy said.

It will work fine (as long as neither vacuum diaphram is leaking.)

 

I've got the same type set-up and just run a t-fitting, off the plenum area. It's been on for 7 years, no problems.
Red

 

I'll T it off, thank you guys!!!!!!!!!!!!!!!!

 

Here's a couple of pictures. 1/8" NPT Vacuum port on rear of intake with a street tee and barb fittings for dist. advance and trans. modulator.

Keeps it clean and somewhat out-of-sight.

 

That helps, thanks RICH B

 

What porkn****** said.............."NOT in a runner........"

4TTRUK

 

No, but since they are common line, a leak may effect both

 

You should be running spark-ported vacuum to your vacuum advance and intake manifold vacuum to the transmission modulator. The one on your center carb is likely above the throttle plate (spark-ported). This would have zero or low vacuum at idle and increase with RPM. If it has tons of vacuum at idle, which drops off when you stab the throttle, it's manifold vacuum. You CAN run manifold vacuum to your distributor (as long as you set your initial timing with the vacuum disconnected), but you cannot run ported vacuum to your transmission.
If you need to make a manifold vacuum port, consider a carburetor spacer with a vacuum fitting.

 

You could get 1/2" thick spacers for the carbs with the fittings on the side...

 

Why?

Vacuum advance system works off manifold vacuum on a regular SBC distributer.

 

Ditto, you need manifold vacuum, and that port is below the blades

 

Actually the vacuum adv. port for a Rochester carb is above the blades on the side of the body BUT it does go down through the body and into the throttle plate and comes out below the ****erflies. The port is above the ****erflies but the source of the vacuum is actually manifold vacuum. You can't always tell by the location of the port. There is no location to get ported vacuum on a Rochester carb. A vacuum advance should have max vacuum at idle Full advance to help keep the temp low in heavy bumper to bumper traffic.

So yes you need manifold vacuum. Check it with a gauge if you are not sure.