Dual Carb Renaissance

[IdubThee]

So I've been breathing some life into my type 3 in preparation of turning the key over for the first time in 5 years. When I parked it, she was running rougher and rougher each time I drove it, to the point where the engine was missing and couldn't idle; it would just die unless i was revving the engine...

..it did seem like the carbs were part of the troublemaking. Anything blatantly wrong with the set-up here? Should It be tweaked? I'm hoping to work with the linkage I have, but there is also this complete package on ebay for $80. Maybe I should start fresh?

http://www.ebay.com/itm/like/121747127797?ul_noapp=true&chn=ps&lpid=82

..by the way, I'm only recently learning about these cars and how to work on them, so go easy.

[Air-Cooled Head]

The troublem w/ ICTs besides no choke, is no balance tube.
You'll have to tap the manifolds and run a tube between them. This will help greatly.
As for your linkage, yours is diff than mine, but I don't see anything blatantly wrong.
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[Erik G]

those fuel pumps put out way too much pressure - you'll want to swap that sucker out
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[Tram]

Ah, another ex fuel injected engine converted to twin controlled vacuum leaks from China... what's not to like?

Is that a crack in the casting next to the volume control screw?

Also your return spring is off.
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[Multi69s]

Come on Tram, you know that deep down somewhere, there is a forgotten love for the dual leaking bricks .

All joking aside, yes you will want to check the output of your fuel pump, and see if it is in the 3PSI range. Also, you are in the process of setting it up, so some things are not connected yet. However, the one thing that bothers me is the fuel line to the driver's side carb (2nd picture). The fuel line seems to be making a rather sharp bend as soon as it leaves the carb. With the questionable quality of todays fuel line, any sharp bend is a place for a problem down the road. I would make the fuel line longer between the carb and the Tee.
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[Air-Cooled Head]

[nogoodwithusernames]

[IdubThee]

Is there a tutorial somewhere for installing that balance tube? Also, what would I be looking at for a new fuel pump? I don't have a pressure tester, so maybe just swap it out and forget about it.



also not a crack by the mixture screw, just residue post clean-up

[Multi69s]

As far as testing the fuel pressure, you can just spend a couple of bucks and get a small pressure gauge just about anywhere. Try and get one that only goes up to about 10 lbs. That way it will fairly accurate at the lower pressures. Install a barb on the gauge and connect it to the fuel line. Do this before spending $$s on a pump. If the pump is close, but has a little too much pressure, you can add gaskets under it to lower the pressure.

As far as the balance tube, does your intake manifolds have a metal tube sticking out of it like this.

Or does it have a plug in it in the location like this one.

If it has the metal tubes, just connect the tube with some vacuum line. If there are plugs, pull them out, and screw in some hose barbs (about 3/8") and connect them together with the vacuum hose. Hopefully you have something, because it will never run quite right without the balance tube.
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69 road Bug 2110
73 Squareback - 2L, T4, Automatic W/ AC
Gone, but many fond memories 69 Baja Bug 2010 - 5 Rib Bus Transaxle
Gone but not forgotten 72 Baja Bug 2010
My builds
T4 into Squareback http://www.thesamba.com/vw/forum/viewtopic.php?t=458944&highlight=
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AC in Squareback https://www.thesamba.com/vw/forum/viewtopic.php?t=...highlight=

[VWporscheGT3]

9 times out of ten , with the symptoms you describe , it was valve lash being the problem all along. that tenth time was the idiot doing the tuning... lol
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[Multi69s]

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Were you there for the tenth time?
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69 road Bug 2110
73 Squareback - 2L, T4, Automatic W/ AC
Gone, but many fond memories 69 Baja Bug 2010 - 5 Rib Bus Transaxle
Gone but not forgotten 72 Baja Bug 2010
My builds
T4 into Squareback http://www.thesamba.com/vw/forum/viewtopic.php?t=458944&highlight=
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[ibldrc]

This is probably not your primary issue, but it isnt making anything better:

The geometry is slightly off with the linkage. Note how on the LH carb, the control arm off the crossbar is slightly to the right of the carb arm

and on the RH side, the control arm is straight on top of it.

This is going to exponentially push the RH side ahead of the left.
In order for the carbs to remain synced through the whole throttle range, the angles and lengths of both pushrod assy's need to be equal to each other, and remain so throughout the entire arc of movement.

There's not much adjustment in your favor with that crossbar linkage you have. You may get better results with a push/pull system.
In general, the crossbar is preferred by the high performance group, but it has to be correctly engineered to be an improvement over the push/pull.
In this case, it isn't.

The farther away from perfect you are with this, the faster your carbs go out of sync when throttle is depressed.

[IdubThee]

Ya. The left one is leaning out. I was thinking about inserting a spacer where i've indicated in this photo. A slightly longer crossbar would help the matter too, I think there is room for it.




To answer your question Multi69, I don't see any tube or plug on the manifold anywhere. I might try and avoid the addition of the balance tube right now if it means engineering a solution. I can't find any specific how-to out there on how to do this and just want to keep the ball rolling with getting this gal running for the first time in a long time. I'm a novice with wrench and might do more harm than good without thorough direction....

[Mike Fisher]

[Air-Cooled Head]

[IdubThee]

So tap the sides of the carbs facing the front of the car... then connect the two carbs with a tube... What type and diameter of tube should I use? Does symmetry matter?

Do you have a picture of your setup Air-Cooled?

[Rome]

Here are some outer diameters of the balance tube outlets from other single-throat dual carb sets. Shown left to right in the photo below.

Stock Type 3 Solex PDSIT: 5/8" (17mm)
Dell'Orto 34FRD: drilled for 3/8" hole (9mm)
Kadron: 5/16" (8mm)

Even though these manifolds are all for single-port engines, the balance tube diameters are the same for the corresponding dual-port manifolds.

Do not use a thin vinyl hose such as a clear aquarium supply. That material will deform when the engine is warm and partially collapse on itself, vastly reducing the ability for the intake pulses to travel within the hose. You can cut a 2' long section of galvanised pipe of the same outer diameter as the balance tube outlets on the manifold, like electrical conduit, etc. and join the ends with rubber hoses that fit onto the manifold outlets. Route the pipe in front of the fan shroud (between shroud and firewall) and lay it on top of the throttle guide tube.

Don't cut your hose too short, since you need to have some slack when you install and remove the intake manifolds. You need to be able to pull the manifold/carb unit up enough with one hand so that you can reach down with a screwdriver to undo the hose clamp on the outlet. 3-4" per side is enough extra hose length for such slack.

[Air-Cooled Head]

[IdubThee]

Can anyone point me toward the procedure for taking out the intake pieces in order to tap for the balance tube... i've never taken one out before..

Thanks



Here is a photo of the type of manifold i'm dealing with... in case it wasn't obvious...

[Mike Fisher]

Go buy 2 - 3/8" hose barbs & 3/8" tap to tap the threads into the aluminum manifolds. Ask the salesman at Home Depot or Ace Hardware etc to help you pick out the parts & tools. Drill & tap them about 1/2 way up at about Air-Cooled Heads "red circle" locations. Drill smaller pilot holes before drilling the big holes to be tapped. Good time to make & install good gaskets for manifolds & carburetors so you don't have any vacuum leaks, that will ruin the performance/tuning. An 8.5" X 11" sheet of thick gasket paper will be plenty of material. You can use a ball peen hammer to cut/make real nice gaskets against the manifolds or just hack them out using just scissors.
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