Dual Weber 34 ICT carbs for 2.0 L bus

[69BahamaYellow]

Helping a friend tune a 1978 bus with 2.0L engine. He's got a brand new "kit" of Weber 34ICT carbs and manifolds from Bus Depot, so I've got a few questions for the experts.

1)What jet sizes work best for the 2.0L type 4 engine (with OEM Cam) and standard dished pistons (will be using a Pertronix SVDA distributor also)

2)when plumbing the vacuum advance for the distributor, is the "ported" throttle plate vacuum port from 1 carb (with the other carb vacuum port blocked) enough for the SVDA distributor, or should we get vacuum from both carburetor ports and use a T fitting to the distributor vacuum can? Yes I know the difference between ported vacuum ports (for ignition timing advance) and manifold vacuum ports (which will be used for the brake booster servo)

3) Does the factory ignition timing specs for the fuel injected bus (7.5 BTDC at idle, 30 BTDC with vac advance disconnected around 3500 RPM) work well for this type of carb conversion or should more / less total advance be used?

4) Will the factory air cleaner assembly for a 1.7 / 1.8 dual carb bus work on these aftermarket Weber carb kits? I'm thinking the warm air intake from the factory air cleaner setup will improve startup driveability, but if anyone has experience with the cheapo dual air cleaners vs the factory setup, please advise.

[timvw7476]

1. the as delivered jetting works well near sea level, I've run them with 1800
as well as 2.0L, same jetting as delivered. Same plug coloring.
although the alcohol in today's fuel takes forever to put color on insulators....
2. I run vacuum advance off the right carb, also feed crankcase breather to it.
Been running a PVC elbow into the topside of the air filter, drilled offset from the carb throat.
3. Yes. stock timing, 28 degrees BTCD up to 30-31 ish BTDC. That's with near stock CR, dished bus pistons, maybe even the factory head gaskets too.( I like them, most hate them. )
4. I never tried to run dual Solex filters to Weber 34s. I assume it's a no go otherwise I'd have seen it by now. The flat filters that come with the kit are rather cheesy, I did replace the original set with the exact same though, makes
routing the breather fumes easy. As far as lack of choke / cold starting, the Webers deliver a decent load of fuel through the accelerator pumps, few taps of the pedal & a properly set up engine fires right away. I've only needed to nurse the throttle at cold starts, well under 40 degrees in winter time.
The one improvement I would add is an electric low pressure fuel pump, makes them act like a modern F.I. engine as far as quick starts hot & cold.

[69BahamaYellow]

That’s awesome news. thanks for sharing that info man. The dual Weber’s seem like the next best option to fuel injection. Was worried about the lack of choke, but as you say, a well tuned engine can overcome that.

I’m removing a center mount progressive that runs awful....

[69BahamaYellow]

Setting up these Weber 34 ICT carbs today to run with Pertronix SVDA distributor. Since there is a ton of mis-information on the internet about using these carbs with a vacuum advance distributor and where to get the vacuum signal from, I thought I'd post this pic to show that the vacuum port on these carbs is in fact connected to the tiny port just above the throttle plate, so this is where you want to connect the distributor advance. I vacuum tested to verify the port was only connected to the hole above the throttle plate and nowhere else. Once I get the bus running, I'll report back on whether it works best with vacuum signal from either 1 carb with second carb vacuum port plugged, or with a vacuum signal from both carbs with a Tee fitting to the distributor vacuum can

[timvw7476]

looks like you're well on your way. Forgot to mention I have tee'd the ports between ICTs in the past. The vacuum advance works either way but I went one port for simplicity. When you set them up I believe a feeler gauge is used to set the blades of both bodies, can' t recall the dimension, .006" ?? After that those stop screws get left undisturbed & the tuning is done via the 'Mixture Screws', which it turns out control everything BUT idle mixture on 34 ICT carbs.
Enjoy !

[69BahamaYellow]

Got the Webers installed and Tee'd the vacuum lines from the 2 carbs together and ran a hose from the Tee to the vacuum advance line on the distributor.

I measured vacuum on 1 carb first and got no vacuum at idle, which jumped up to 10 in Hg when you barely crack open the throttle, and falls back toward zero as you open the throttle further. It's working exactly as it should to give a vacuum signal, right where you need it (part throttle / light load)

Next I teed the 2 carb vacuum ports together and got similar measurements, with 10 in Hg maximum vacuum recorded. The main difference is the vacuum signal is "cleaner" with 2 carbs Teed together. With only 1, the vacuum gage needle bounced a lot, with 2 carbs, it was pretty steady. Should have measured vacuum separately on the 2nd carb for comparison (just in case there's a valve or compression issue on 1 side of the motor), but the clean signal from 2 carbs tied together convinced me that is the way to go.

I then used my vacuum pump on the distributor vacuum can to see how much is required to open it all the way up. At least on the brand new Pertronix flame thrower SVDA, I'd say 10 in Hg advances the breaker plate 95% of it's full travel. It took about 15 in Hg to move it all the way. When I check timing with engine running, the vacuum signal from these carbs adds 8-9 deg. of advance to the mechanical advance and unlike a mechanical advance only distributor, the advance comes on almost instantly, when you crack open the throttle. It really does make a noticeable difference in driveability. With the mechanical only distributor, the bus had a noticeable flat spot on initial acceleration and it really took off at higher revs when the mechanical advance started kicking in. with the vacuum advance distributor, you get instant acceleration, and it's smooth all the way to full throttle. Don't know why anyone would use a mechanical advance distributor (even though the instructions that come with these carbs state to use one in BOLD print)....

[69BahamaYellow]

Dang it. Just got the carbs tuned and it idles and revs beautifully, but drives awful. It's good at idle and full throttle, but pretty erratic everywhere else.... Was hoping the as supplied jetting would be close, but it seems that is not the case. As supplied from Bus Depot, the jets are as follows:

52 Idle, F78 Emulsion, 160 Air, 130 Main, 175 Needle, 40 pump spill

I found a site called Wayoutwestie that has tuned these Weber 34ICT carbs for a 2 L bus motor and generously provided their recommended jets as follows:

55 Idle, F6 Emulsion, 185 Air, 165 Main, 150 Needle, 40 Pump Spill / Recommended setting float height at 8mm (instead of Weber recommended 6.5mm)

Will report back how the new jets and settings change things.

[timvw7476]

that 'erratic everywhere else' but idle & acceleration has me concerned......
There are a few possible restriction paths in the fuel system, the sock at the outlet of the tank, inline filter, & the little guy built into the mechanical pump bolted to the engine. Oddly, these buses will actually try to run even with just gravity feed through some of the electric pumps but not through others. ( I mean even when there's no 12 VDC supply to the pump)
I don't see any mention of the pump system you're using but check for pressure. Three pounds is all it takes to feed them. A little less than that & you get tiny backfires & slow performance as the floatbowls run low.

[69BahamaYellow]

Yep. You were right. hot wired the facet electric fuel pump and got no pressure. Gravity feed only. The crimp on power wire to the fuel pump had pulled loose. Reconnected that and I'm getting 3 PSI.... Going to re-set my float levels (they were off anyway) and try out the as supplied jets again.

[69BahamaYellow]

Reinstalled as supplied jets, synced carbs, tuned to “best lean” and went for a test drive. Much better this time. Bus starts to accelerate immediately when you hit the gas, but there’s an annoying stumble and surging as you give it more throttle through the transition port openings. At half throttle it smooths out. Think this could be the emulsion jet?

[Alan Brase]

Does this system use a crossover between the left and right manifolds? I would certainly add one and then tee the vacuum brake booster from that. Keep in mind every factory 2 barrel system used a crossover. 72-74 used 2 actually. Old single barrel Solex Porsches used crossover.
The crossover evens out the idle and transition a little. The firing order on these is 2-1, 4-3. So what each carb feels is: suck suck, wait wait. So the second cylinder on each side is being a little shortchanged.
Your idea about using the original air cleaner is an excellent one. You need preheated air even more during slightly warmer, more humid times.
"California- Bolt-on" is a term an old friend told me many years ago.
Glad you got rid of the progressive. Never witnessed one working right.
_________________
Al Brase
Projects: 67 sunroof bug, 67 Porsche 912 Targa, 70 Westy
Dec 1955 Single Cab pickup WANT 15" BUS RIMS dated 8/55, thru 12/55
To New owners: 1969 doublecab, 1971 Dormobile
Vanagons:
80 P27 Westy JUL 1979, 3rd oldest known US
83 1.6TD Vanagon, 87 Wolfie Westy daily driver, swap meet home

[timvw7476]

[airschooled]

Wayout Westie’s ICT specs have always driven excellent for me. Emulsion size/style is very important on those.

Robbie
_________________
Learn how your vintage VW works. And why it doesn't!
One-on-one tech help for your Volkswagen:
www.airschooled.com

[69BahamaYellow]

All good points. Yes, I used 12mm braided cohline hose to connect both manifolds and teed that to the brake booster. I tested the balance hose with a vacuum pump to make sure it didn’t collapse under vacuum, and it didn’t distort under 23in vacuum. Thought about fabricating a metal balance pipe but it wasn’t necessary. I can confirm the balance pipe makes a big difference in smooth running.

Wayout Westy describes all the symptoms I’m seeing as being attributable to the as supplied jetting with these carbs. They are really not bad, and much better than the center progressive but using my bus with factory L jet injection as a reference for how they should run, the 34 ICT Webers are not in the same league at the moment. I can live with the lack of choke and the extra noise from the silly EMPI air cleaners but the stumbling through part throttle has got to go

[69BahamaYellow]

Here's what the Bus Depot kit looks like installed.

Notes about this kit so far:

1) Installed carbs on opposite sides (from what the instructions indicated) so the linkage would be on the firewall side of the engine bay. This allowed me to setup the linkage without a throttle cable extender, but I had to fabricate a Heim joint with a welded on barrel connector to accommodate the odd pull angle. I also had to cut down the 3/4 side lever on the hex bar to clear the firewall tin, so in hind site, maybe a cable extender, with the hex bar on the engine lid side would have been easier. Other than those issues, the EMPI linkage works pretty well. Setting the throttle pull on the bottom hole of the lever and the carb links on the middle hole of those levers allows the throttle plates to fully open when the accelerator pedal is depressed all the way to it's stop, and the throttle plates fully close when you let off the gas. The linkage is very smooth and it's easy to set the links so each throttle plate opens exactly the same throughout the full stroke. I had to add an additional spring to the throttle cable lever to pull the long throttle cable all the way back, as the springs on the carbs are not enough to do it. The EMPI kit came with the plate to mount to the engine, but no springs.

2) The short EMPI manifolds with thin gaskets initially concerned me that the carbs would overheat and boil off the gas from the float bowls after a drive, but so far that does not seem to be the case.

3) The manifolds did not come with hose connections for the balance pipe so I had to order 2 brass 1/4" MIP to 1/2" Barb fittings to accomplish the task. 1/4"MIP to 3/8" barb addapters are readily available at Lowe's and Home Depot, but the 1/2" barb is not as easy to find. With a single barrel feeding 2 cylinders each, I felt like a larger diameter balance pipe with less restriction at the manifolds would be better, and as well as the balance pipe works on this setup, I believe this is the case

4) As mentioned earlier, the vacuum advance ports on these carbs work beautifully. When I use my timing light and barely crack open the throttle, I get instant timing advance at low revs and the engine responds with quick acceleration. You also notice the timing advance when you get up to cruise speed and back off the throttle. you can feel the timing advance coming back in to give some extra pep under light engine load. Where I really notice the difference is on small rolling hills. with the old mechanical distributor, you would have to give more throttle to get over the hills, but with a vacuum advance, the engine has the beans to clear the hill without adding much throttle. Time will tell, but I feel like this will make a difference in fuel economy.

This engine was a mess, before I started. There was no foam seal around the engine, and there were several missing pieces from the engine tin. There were no cooling flaps installed, so I also added these and a working thermostat. I also had to seal up the holes from missing heater ducts and a big hole in the body from a prior A/C compressor install. My friend was complaining about the bus overheating (can't imagine why ) I did the customary valve adjustment prior to getting started with the carb tuning, and nearly all valves were loose. This is a hydro engine, so there should be none (2 turns in on the adjusters, engine cold). Compression numbers are #1-150psi, #2-130psi, #3 and #4 - 112 psi, so the "overheating" damage has already been done. The old center mount Weber progressive was totally hacked together with non matching pipes and JB welded on fittings. Tons of vacuum leaks. You can make the center mount carbs work, but this one wasn't even worth trying, so that's what led me down the dual carb path next

I'll add one last note on the distributor. I replaced the old Bosch .009 with a pertronix SVDA, as I've had really great success with this one on my own 78 2.0 bus. The new Pertronix manual emphasizes replacing the solid core spark plug wires with wound "mag" core wires to prevent EMF interference messing with the pertronix ignitor over time. The one on my bus failed recently after years of trouble free running, so I'm wondering if Pertronix may be on to something with the new recommendation for wound wires. They also emphasized using a 3.0 Ohm coil max. The Bosch Blue coil that was on this one measured almost 4 Ohm, so I replaced both the coil and plug wires with Pertronix brand ones. The wound core pertronix plug wire set is for a type 1 motor, so you have to fabricate some extenders for the #2 and #4 cylinders to get them past the cooling tin. The plug end connectors are crimped on, so you can't just use your old ones on the new wire set. Kind of a pain....

[69BahamaYellow]

Got new jets from carburetors unlimited in Seattle today and I can confirm that Wayoutwesty’s recipe for jet sizes and 8mm float height have this engine running tip top. With the setup he recommended, my final mixture screw setting was 1-1/4 turns out on each carburetor to reach “best lean”. Carb sync was set at 7 on the syncrometer to give steady 925 RPM idle. Now that it’s running so well, I can confirm as others have that the short EMPI manifolds put the carburetors too close to the hot cylinder heads and it will boil off the fuel after a drive. I watched it bubbling up through the air jet into the carburetor throat, And measured 140° on the carburetors after a 5 to 10 minute heat soak. I’m going to try phenolic heat isolators next. Read on the Late Bay that you could make 2 isolators out of a single head to manifold gasket. Sure enough you can. Will see how this works tomorrow

in the meantime I added in evaporative charcoal canister

[69BahamaYellow]

The heat isolator between the manifold and carb made a big difference. The same drive and air temperatures that resulted in 140 deg carb temps about 10 minutes after engine shutdown and gas percolating out of the bowls with just the supplied gasket now results in 100 deg carb temps after 10 minutes heat soak and no fuel percolating. Ambient air temp was 74 degF. Cylinder head temps were 275 degF right after engine shutdown.

Now that the bus is running like it should I'm wondering if anyone has considered some kind of electric or vacuum operated fuel shutoff valve when the engine is not running for carburetors in general? It occurred to me that, for a bus, fuel can "gravity feed" into these carburetors with the engine running or not. It actually gravity feeds through the electric Facet fuel pump on this bus pretty well (not sure if the mechanical pumps have that problem). Regardless, the only thing stopping all that fuel from ending up in your engine crankcase are the needle valves in the carburetor(s) I've never seen a carbureted motorcycle without a manual or vacuum operated shutoff valve on the fuel tank, and I've seen plenty of them with crankcases full of gas (after sitting for a while), when someone forgot to shut off the fuel valve after the last ride....

[crownline]

There are posts on here about shutting off the fuel using relays. It's early so I'm not going to search for them. Thanks for the info on making those carbs work.
_________________
1972 Bus 1700 cc Single Carb. But not a progressive.
Barelymuvin
Wish I still had the ones I got rid of.

"It"s got some dings and dents and neither of us is going to SEMA."(Update, I went to SEMA in 2019 but the Bus stayed home)
[url=http://www.vw-mplate.com/mplate-8446.png]Click to view image[/URL]

[HoboBus]

This isn't a mechanical shutoff, but it is a fuel pump controller that I thought was pretty cool.

Primes the pump for 3 seconds at startup, and shuts the pump off if the motor stops.

Pretty cool.

https://www.classicindustries.com/product/re12003....gIkxPD_BwE



.
_________________
Salt air it ain't thin, it'll stick right to your skin,
it'll make you feel fine. Makes you feel fine.
And I wanna be there. -- Jimmy Buffett

Just a beach-oriented camping Hobo with a bus.

[k@rlos]