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Weber ICT Balance tube
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Paul Wilson
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PostPosted: Sat Jul 09, 2011 5:21 pm    Post subject: Weber ICT Balance tube Reply with quote

I am very aware that the dual single barrel carbs need a balance tube. My 66 Squareback has one and is is a single port engine. Do dual port engines need another balance tube ? Is there any advantage to using two balance tubes? Front tube for 1 & 3 cylinders and a tube in the rear for 2 & 4 cylinders? Has anyone tried this?
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Erik G
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PostPosted: Sat Jul 09, 2011 7:07 pm    Post subject: Reply with quote

yes it needs one. maybe even more so than a single port. Never tried running more than one
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Paul Wilson
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PostPosted: Sun Jul 10, 2011 7:29 am    Post subject: Reply with quote

Erik G wrote:
yes it needs one. maybe even more so than a single port. Never tried running more than one


Yes, I knew dualport engines need one, I just wanted to knoe if anyone had used two balance tubes.
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mxracer
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PostPosted: Sun Jul 10, 2011 7:45 am    Post subject: Reply with quote

Don't know if they NEED dual balance tubes but I'm assuming it does help. The dual carb 71 models (I'm assuming European) had dual balance tubes from the factory according to the Henry Elfrink manual I have. I thought about doing it to mine as well.
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Mike Fisher
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PostPosted: Sun Jul 10, 2011 8:05 am    Post subject: Reply with quote

The single balance tube on dual port engines is hooked to the intake manifolds not the carburetors. Dual balance tubes sounds redundant/unnecessary.
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Paul Wilson
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PostPosted: Sun Jul 10, 2011 8:09 am    Post subject: Reply with quote

Mike Fisher wrote:
The single balance tube on dual port engines is hooked to the intake manifolds not the carburetors. Dual balance tubes sounds redundant/unnecessary.


You are right, the tube does connect to the manifold. But on the dual port manifolds it would only balance the no. 1 and 3 cylinders and not the no. 2 and 4 cylinders?
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Mike Fisher
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PostPosted: Sun Jul 10, 2011 12:24 pm    Post subject: Reply with quote

I would think that the vacuum probably draws all the way into the sump and all 4 cylinders end up equal? Think
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PostPosted: Sun Jul 10, 2011 1:44 pm    Post subject: Reply with quote

Paul Wilson wrote:
Mike Fisher wrote:
The single balance tube on dual port engines is hooked to the intake manifolds not the carburetors. Dual balance tubes sounds redundant/unnecessary.


You are right, the tube does connect to the manifold. But on the dual port manifolds it would only balance the no. 1 and 3 cylinders and not the no. 2 and 4 cylinders?


If you look at the dual port manifold, you'll see that it's pretty open up near where the carb attaches. That's where it gets it's vacuum from the 2-4 side of the manifolds. Yes, the vac signature is probably stronger on the 1-3 side of the manifold, but it does balance out. On the OE VW manifolds, they pull vacuum from the center of the manifold, so it's more evenly spread out between the 2 cylinders on each side.
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PostPosted: Mon Jul 11, 2011 12:21 am    Post subject: Reply with quote

mxracer wrote:
Don't know if they NEED dual balance tubes but I'm assuming it does help. The dual carb 71 models (I'm assuming European) had dual balance tubes from the factory according to the Henry Elfrink manual I have. I thought about doing it to mine as well.


having an euro '71, I don't think the dual balance tube make a big difference (it surely does make vacuum leaks more likely!), actually they only used them for part of the year and then went back to a single balance tube (but still taking the vacuum from the 4 ports)
Now I don't remember if in my car vacuum to the modulator for the trans is taken from the 1-3 or the 2-4 tube, I'll check just out of curiosity
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PostPosted: Mon Jul 11, 2011 7:50 am    Post subject: Reply with quote

If you have single/dual carbs, you want to run a balance tube. If you have dual/dual carbs, you don't.

Wink

Dual ICT's - The balance tube should be hooked to the threaded part on the manifold that grabs vacuum from both intake ports. It's just under the flange the carb bolts to. So no need to have multiple balance tubes.
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PostPosted: Mon Jul 11, 2011 3:25 pm    Post subject: Reply with quote

Slow 1200 wrote:
mxracer wrote:
Don't know if they NEED dual balance tubes but I'm assuming it does help. The dual carb 71 models (I'm assuming European) had dual balance tubes from the factory according to the Henry Elfrink manual I have. I thought about doing it to mine as well.


having an euro '71, I don't think the dual balance tube make a big difference (it surely does make vacuum leaks more likely!), actually they only used them for part of the year and then went back to a single balance tube (but still taking the vacuum from the 4 ports)
Now I don't remember if in my car vacuum to the modulator for the trans is taken from the 1-3 or the 2-4 tube, I'll check just out of curiosity


I had a set of VW manifolds here that had a plastic "F" connecting the 2 ports on each side with a single outlet. I suppose you could have used 2 hoses to tie both sides together (run 2 balance tubes) if you wanted. But my thought is that it would look more crowded with the extra hose in there. Wink
On my wife's Fastback (back when it had carbs), the AT modulator was connected to the balance pipe that tied both sides together.
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