Running Weber Ict’s on a Vw aircooled engine 6

Weber ICT’s Updated 26/05/24

Introduction
If you find yourself here you have either just bought a set of weber icts or are struggling to set them up/ have fuel in your oil/ starting issues or bogging down. I rebuild/ install on average 3 kits a week and through experience know what makes them work and what makes them fail. Please read the below and take the information on board, if you miss a step or run your engine without one of them, know that you will have an issue, either straight away or in the near future.

I hear comments daily such as “I just bolted them on and I’ve never had any issues”. As part of my vw aircooled workshops, I teach that Vw aircooled engines by design are very forgiving, they are low compression, low revving and will keep going on and on for 1000’s of miles even with running issues including high fuel pressure and incorrect jetting. They will take a lot of punishment and run with a hole in a piston, with worn rings, bearings and valves or even on 3 cylinders…but when they die they will die in a spectacular way.

If you are having running issues with your ICT’s or are considering a conversion please don’t hesitate to contact me. I provide workshop services to install, and mobile services to rebuild and rejet Weber Ict’s. For further information please contact me here

To see how to inspect, setup and replace you floats and needles please check out my youtube video

What’s Available?

Weber ICT’s are my favourite carbs, in my opinion they offer the best performance/ economy combo for any T1 engine up to 1776 and Type 4 engines up to 2 litre. They are still available new and produced by Weber in Spain. I obtain them directly from the supplier and rework them so they are ready for you to fit. I supply fully prepped kits, jetting kits and parts for Weber ICTs.

Click here for available kits

Click here for jetting kits and services 

Avoid empi kits, manifolds and linkage.

T1 Engines should use a csp bellcrank linkage with cbperformance manifolds or CB linkage & manifolds.

Type4 Engines should use a cb performance manifold and linkage kit.

Please note ;

T1 engines must utelise the stock oil filler breather to atleast one carb filter.

Type 4 engines must utelise the case breather box outlet to atleast one carb filter.

Late bay/ US & Cali spec and T25/Vanagon may have to feed fuel tank breathers to the carb air filter or separate outlet. The spring flap air inlet will be made redundant but can be left in place.

Aircooled T25’s may struggle with the filter height of the CB performance kit. It works but it’s tight.

I put this article together because like many people I was frustrated when I first bought them (15 years ago) and realised that they wouldn’t run even close to right out of the box. However many many sets later on various different vehicles and engine sizes I decided to put my experiences on paper and share it with you. There is a wealth of information on the internet on these carbs but I have to say much is outdated of doesn’t cover all of the issues you can face as soon as you open the box.

Your engine should be in good tune
To save you searching and swearing like a big ugly vw shaped sweary thing I have put together the below for you….

Firstly your engine needs to be tuned and timed and otherwise running well before fitting your new carbs. If you have running issues already don’t fool yourself that fitting new carbs will solve all you problems. It won’t. It will also make setting up these carbs a complete bastard!

What kit?

Go for CSP or CB linkage or you will have linkage issues. Trust me.

If you have a new set and you do nothing but fit them and hope for the best, they will run like crap, even when balanced and setup as per the instructions. This my friends is completely normal. This is partly due to the fact most suppliers send out carbs with ball park or incorrect jetting (because the carbs were not originally designed for aircooled vw’s). However its not all their fault as in reality carb jets are like shoes, just because two people are a size 10 it doesn’t mean the same shoe will fit unless the two people are identical twins. The same goes for engines, no two engines are created equal unless you have blueprinted spec, ancillaries and they happen to be made in sealed lab type conditions.

There are a few issues that I come across and hear people struggle with often. They are simple to over come and when you take the time to get them right you will be well on your way to a sweet running vdub 🙂

There are 5 issues you need to resolve before they will run right.

No kit will run out of the box

1.When you receive the carbs, the first thing you should do is strip them. Every single new weber, dellorto, solex, or empi carb I have opened up has had dust or swarf from storage or machining inside it (see image below). This will block your jets if not cleaned thoroughly. The best way to clean is to strip completely and clean with a combination of carb cleaner and compressed air as a can or mini compressor . You can’t rely on just carb cleaner. You should be checking your float level and what jets are installed anyway so stripping them down is no biggie.

2. I feel like screaming it from the heavens when I come across a new post about weber ICT poor running….Change the emulsion tubes as they are supplied wrong F78 (for Bedford vans). Change them to F6, or if you can’t find them F3’s (located under the air correction jets) .

These make a big difference. My first experience with these carbs some years back had the engine stalling, backfiring and refusing to start when hot. It drove me nuts, I had stripped the carbs, rejetted a silly amount of variations, triple checked timing, spark, fuel pressure and everything else and they still ran like shit……..all due to the emulsion tubes. Once I changed them BINGO they ran 90% better. The remaining 10% was fine tuning.

Most suppliers get close but sadly refuse to accept that they ship them with the wrong emulsion tubes and jets. I have purchased 1000’s of sets for various vehicles over the years and have never be jetted right, you need to request the correct jetting for your engine size (see below). I want to make it clear however that the quality of carbs if genuine Weber are unsurpassed, I will always buy genuine carbs from them. When you are changing the emulsion tubes remove all other jets and blow them through with carb cleaner and compressed air.

3. Ensure you have the right fuel pressure of 2.1psi. 2.1-2.5 is preferred, whatever the lowest number is where the pressure is constant when you rev the engine. Weber ICT’s run like crap when they overfuel.

Prior to 2021 I always ran and installed Low pressure Huco electronic pumps with 2.1 psi. Sadly these have all been faulty in the later part of 2021 and I stopped using them in 2022. The fault was that the pressure output was actually closer to 4.5psi and the pumps pulsed. Both high pressure and pulsing damages needle valves in very short order.

The bigger manufacturers have stopped selling them but they are still available in some places. Avoid them and if you have already bought one you need to test your fuel pressure ASAP.

No matter what fuel pump you run (stock or electronic) you need to use a pressure regulator set to 2.1psi or you will end up with leaking needle valves and fuel in your oil.

I recommend and use a malpassi malpassi petrol king or a malpassi filter king with 6mm hose ends on all my kits.

One way valves – available here

These work by opening and closing at a pressure of 2psi. Therefore if you switch of your engine the, pressure from your fuel pump will drop a the valve will close. Even if you have leaking needle valves this is a really good fail safe to stop fuel from entering your oil.

Pressure regulators often come with an inline one way valve. I used to advise to ditch them as out of the box they leak and are a poor attempt to overcome the symptom caused by over-pressure (leaky float valves).

I still advise to never fit them out of the box,  however if you fully take them apart (both ends and central seal) and seal them with loctite 577 thread sealant they work a treat and are a great failsafe against getting unwanted fuel in your oil.

I usually use a petrol king stand alone pressure regulator as opposed to a filter king, the reason is any filtration needs to come before the fuel pump and any pressure regulation needs to come after the fuel pump. The filter king regulator and filter all in one is a bit pointless for that reason.

Malpassi / Sytec Petrol king with 6mm Barbs – click for purchase link

If you don’t regulate the pressure the symptoms are stalling, bogging down, difficulty in starting, large backfires…..pissing off the neighbours. You will also wear out your float valves (needle valves) due to over pressure, this causes the floats to never completely shut off the fuel flow and over time will cause a slow drip of fuel to trickle down the throat of the carb and in to your sump when stationary. Shortly after you will have a smelly puddle on the floor and a scrap engine due to fuel contamination in your oil causing a lack of lubrication.
Also don’t be tempted to just add some gaskets to your pump pedestal. It’s an old school way of reducing fuel pressure but it doesn’t eliminate pressure spikes as is not regulated and can cause pressure issues.

You will need an inline fuel gauge to test the fuel pressure. These are cheap on eBay. Be warned they are for test purposes only, don’t drive with them fitted!

4. The carbs have a vacuum take off for a reason. With a non vacuum 009 distributor it always causes hesitation and a flat low down throttle response. Do you have no flat spot or you have the vacuum ports blocked and all seems OK? That’s because you carbs are running very rich and its masking the issue. Once properly jetted it will be a different story.

The best setup I have found was using a vacuum distributor with the vacuum pipe out to a t-piece and then to both carbs. You can get away with one but connecting two makes it that much smoother. If you fit both then ensure you also fit an anti-pulse valve inline. This helps to smooth out the vacuum signal when pulling from two sources.

The port is located as per the image below :

5. Manifold choice is important.

The empi and copycat ecl manifolds not only don’t come with a balance pipe outlet but they are very short and poorly made. This causes heat transfer between the cylinder heads and carbs and can boil your fuel! This causes the fuel to vaporise and eventually pushes its way past your float jets where it re-condenses and ends up in your oil. The boiling fuel has been known to cause the plastic float halfs to come apart. The floats are assembled in factory as two halfs stuck together with glue. As the boiling fuel temperature exceeds the glue melting point they start to take in fuel and sink.

Only use I CB Performance manifolds and due to the issues with needle valves more recently, took the decision to always use heat spacer gaskets as a precautionary measure.

These can be purchased here

Here is a side to side comparison between the empi and CB performance manifold, notice the height difference and balance pipe outlet on the CB performance (right)

Another important aspect of the carbs is of course balancing. A balance pipe is a must between the two manifolds for a smooth idle. Another good reason to get the CSP or CB kit is that they come pre-tapped for a balance pipe to be fitted.

Initial setup

Please note the distances between parts in the video below. In order to maintain the correct fuel pressure, for the one way valve to work and to get an accurate fuel pressure reading when setting it up, please use a minimum of 30cm between each part as a guide.

A good way to initially balance the carbs before installation is to ensure the butterflies open the same amount. To do this turn the carb upside down and open the butterfly. Put a feeler gauge between the butterfly and the inside wall and use a feeler gauge to check the gap. 4 thou is a good setting, adjust the idle speed screw until a its a snug fit between the butterfly and the side of the wall. Adjust both carbs to open the same amount. This will ensure equal airflow upon first start up. The idle stop screws need to return under tension to their resting position you have just set. When you attach the linkage after making your adjustments you must ensure this is still true. The linkage if too long or short on either side can cause one of the idles to open or close prematurely. Once you are up and running you need to return to this and check.

For first setup only your mixture screw should be 2 1/2 turns out. Screw them all the way in (lightly) and then 2 1/2 turns out.

These are base line settings to get you up and running, you will need to do further fine tuning once the engine is warmed through.

Jetting :

I have spent years jetting engines from 1200-2110cc. Below is the jetting that works, its not ball park, its not theory its 20 years of research, practice, rolling road tests and 10000’s of miles on the road. It’s also partially taken from the original jetting Volkswagen themselves used on twin carb setups.

The Issue with Rolling Roads :

ICT’s are singe barrel carbs feeding dual cylinders, as such you need to run them richer than dual barrel carbs to avoid ‘fuel stand off’ caused by manifold pulsing. This is where some of the fuel is lost into a fine mist and remains trapped /suspended just above the carb. A richer set up helps minimise this affect as well as linking the two manifolds together. Unfortunately many garages including well known VW ones who shall remain nameless ignore this fact and just shove them on a rolling road, guess what…they run lean.

Every rolling road I have used to test Weber ICTs ended up Jetting them incorrectly. Weber ICT’s feed a bank of two cylinders per carb and Aircooled engines need to run on the rich side.

Using a gas analyser and rolling road on paper works with these carbs, however after extensive testing I have found the jetting to end up lean, with spark plugs ending up white, engine temperatures being raised and in many instances piston rings being damaged.

Rolling roads also don’t necessarily change emulsions, float heights or even realise that fuel pressure is so vital with Weber ICTs.

The jetting below are based on stock to near stock engines. No wild cams, big big bore free flow exhaust systems or significant head work. If you have had those kind of upgrades then these jets will be a good starting point for you but, that is the time a rolling road will work for you and the only time one should be used with these carbs. Note a stock 1776 with electronic ignition and a vintage speed exhaust is not considered wild or very far from stock.

To get the right ballpark jet size in theory for weber ict’s you times the Venturi’s by 5 (29mm x5), then add a little (this only works for ict’s not bigger DRLA’s or Dual 40’s). This brings you to 150 main jet, you then plus 20 for the airs 170. This size difference between the main and air jets is taken from VW’s own twin carb setups, it works.

You will find the idles at 55 supplied are OK no matter what engine size you have, if you need to make them bigger you are not running a stock engine or you are running a 009 and are suffering from a flat spot. The needle jets for the floats are usually supplied at 175, this is too large and attributes to over-fuelling, generally 120-140 is the best setting but recently I have only been able to find needle jets at 150 which still work well. As mentioned above the emulsions need to be F6 not the F78 supplied which causes over-fueling and stumbling off idle, the engine to cut out or not start at all!

Those are your ballpark jets for your 1600 however they are not real world figures. In practice I ran a 1600 and 1641 on the above and found it to run a too rich. 145 mains, 55 idles, 165 airs, F6 emulsions are spot on.

Please note all jetting is at sea level

Type1 :

1300 130 mains, 150 airs, 55 idles, f6 emulsions, 150 viton tipped needle valves.

1500 140 mains, 160 airs, 55 idles f6 emulsions, 150 viton tipped needle valves.

1600/1641 145 mains, 165 airs, 55 idles, f6 emulsions, 150 viton tipped needle valves.

1776 160 mains, 180 airs, 55 idles, f6 emulsions, 150 viton tipped needle valves.

Type4 :

1700 155 mains, 175 air, 55 idle, F6 emulsions, 150 viton tipped needle valves.

1800 160 mains, 180 air, 55 idle, F6 emulsions, 150 viton tipped needle valves.

2 litres 165 mains, 185 air, 55 idle, F6 emulsions, viton tipped needle valves.

On stock and mild engines with stock, heads, cams, rockers, electronic ignition and freer flowing exhausts the above will work. Leave the pump jet and spill valve as supplied at .50pump and .40 spill.

Jet Locations

Float Height – Updated 01/07/19

Floats are never set correctly from the manufacturer and can cause numerous issues. You must check the height before the carbs are installed.

Remove the floats and weigh them, they should be 10.7-11g. if out of this range they are potentially leaking and need to be replaced.

Over the last two years there has been a change in the needle valves which has caused them to leak at the standard height of 6mm. Even with new 150 sized valves and the correct fuel pressure they would not shut off.

Since the valves have changed I now set all weber Ict’s to 8mm and use Victron tipped valves. The top part of the carb should be taken off and sat vertically and the float allow to swing freely. With the paper gasket fitted the measurement is taken from the top of float to gasket as in the below image. Ensuring you are not compressing the sprung loaded ball on the needle. You adjust the float by bending the metal tab that bears against the needle.

How to test and replace your needle valves and floats :

Linkage

The best kit for T1 engine in my opinion is the CSP linkage followed closely by the CB performance hexbar.

The CSP is a a bell crank push-pull type which is the closest thing to fit and forget as they come! The build quality and instructions from CSP were excellent.

For a Type 4 engine you can’t beat the Cbperformance kit. It even comes with an additional tap for your servo vacuum.

Fine tuning

Double check the settings above. If you have a mechanical pump you will need to winch over the engine a while to fill the floats. If you have an electronic pump turn the ignition to the first and run the pump and pressurise the system. Start the engine. Rev the throttle a little to ensure enough fuel mixture is pushed through the engine and bring the engine up to operating temperature. These carbs have no choke so they will need a bit more warming up than a stock carb. When the engine is warm enough to maintain idle speed, you will need to better balance the carburetors.

The first thing I do is to disconnect the linkage at the carb ends, this is to ensure any adjustments that are made are not being affected by mis-adjusted linkage.

If you followed the instructions above and your butterfly setup was accurate, and if your linkage is correct so that the throttle stops rest on the idle speed screws, your engine should be in the ball park. If your idle speed is much too fast, turn the idle speed screws outward 1/8″ turns each, make sure they are matched and keep adjusting equally until the idle speed is reduced and your engine is ticking over at a good approximate speed.

Reset your mixture screws but turning them in a quarter of a turn at a time until the engine starts to stumble, then turn it out 1/4 to level out and then another 1/4 turn.

Grab your airflow meter and take off the airfilters on your carbs. The meters come with two rubber tubes, remove the smaller one and place it on top with the larger rubber mount only. Take a reading, usually they start at 10+, you are aiming for both sides to read the same, this usually works out to be a reading of 6-7. Please know if your timing is not correct balancing and tuning will never be correct so do it now before proceeding!

Using a rev counter you ideally want to see a rpm of 900-950. Check the carbs with the sync meter and adjust half a turn at at time until they are both reading around 8 initially. Then check your rpm.

Adjust both sides until you hit 900-950 rpm, there is usually a sweet spot where then engine is smoothest.
I find a value of 7 is usually the closest to the correct rpm of 950 if your timing is correct. Done sweat it of it’s a bit higher or lower as long as your timing is spot on and your carbs are balanced.

At this point if the engine is ticking over nicely and the carbs are sync’d, you need to reset the mixture screw again, repeat the process above and then check your carb balance with the gauge. At that point you will need check the rpm again. You may need to go back and forth with the above several times but after 2-3 adjustments you should be good.

Please note during the above tuning phase to your engine may be running rich for some time at idle. This on occasion fouls the plugs causing one or two to not produce a spark. If this happens you will find that one of the mixture screws will make no difference to the tuning. The resolution is to remove your spark plugs, clean them, gap them and re-install. Then start the engine and tune in the carb.

Loosely offer up your linkage, adjust so it will go back on without opening or closing the throttle. Pop it back on with the engine running and listen carefully for any change in pitch of the engine, you need to ensure that the idle stops can nicely rest without being pushed or pulled by the linkage. If the revs increase and popping the on opens one of the carbs when you re-fit you will need to adjust the linkage so that it doesn’t.

Note that adjusting one side can open the other side.

When all seems good switch off the engine, check that both carbs open at the same time and return fully. Only then should you tighten the linkage fully.
Lastly attach the throttle cable, ensure not to do it too tight. Get someone to put their foot on the pedal whilst you look at the carbs, ensure full throttle is obtained and that both carbs return fully.

Take the vehicle for a hot run, around 20 minutes of varied driving including high speed. As soon as you get home don’t turn the engine off, jump round to the engine and reset the mixture screws. JOB DONE

Hot and Cold Starting Procedure

When you start you have to bear in mind that you have no chokes. Your engine needs lots of fuel to get going when cold. So pump that pedal 2-3 times, hold the throttle open a little and crank the engine!! Keep the throttle open and rev once in a while until its warm and will tick over by itself.

When hot it can tend to over-fuel (especially when you are still fine tuning) so press your pedal GENTLY to the floor (so as to release as small amount of fuel as possible) and hold it there. Start your engine and if it takes a while to start that’s ok….just don’t be tempted to pump the pedal.

Airfilters & Breathing

Dependant on the kit you purchased you will either have the pod style or cb style air filters. Both are gauze mesh type and will need airfilter oil to catch all nasties. I highly recommend that one or both of the filters are tapped and linked to your breather system. This is the only way to get any sort of pre-heat and negative pressure in your case. It will help with cold starting and allow for any excess pressure to be vented. I usually run a cheap EMPI breather out to both carbs and to an aftermarket oil filler. On smaller engines up to 1641 that’s ok, but any bigger and I usually add an additional breather outlet to the stock pump hole. I then tap the breather box to create an additional inlet and feed the box out to both carbs.

Over-fuelling problems

As mentioned above the weber ICT’s are very susceptible to over fuelling. The main issues I see are :

Incorrect jetting (specifically the emulsion tube)

High Fuel Pressure exceeding 3psi

Worn out needle valves causing the flow of fuel to never completely shut off. Note the ring around old jet where the over pressure has worn it out.

To see how to inspect, setup and replace you floats and needles please check out my youtube video

If this article helped keep your bus or beetle on the road, drop me a line I’d love to hear from you!
All Weber ICT kits, jets and parts are available on the Wayoutwestie shop

Why not roll with a Wayoutweste sticker, now available on the Wayoutwestie shop.

Click me 😉 go on you know you want to!

Testimonials from some lovely people :

Just finished a 1641 rebuild and it ran ok with the out of the box jets but did have a very mild flat spot on transition to mains so I followed your advice on jetting and I can’t believe how much better it is! Smooth all the way through and noticeably more power after the rejetting.
Thanks for your advice it’s very much appreciated. I wouldn’t have known were to start without your detailed advice 👍

Cheers

Andrew