The most important part of your Weber Carburetor rebuild is cleaning. But what is the most important part of the cleaning? It is cleaning out the fuel passageways, or galleries. Surface cleaning is great but opening up and chasing down the galleries is essential.
In this lesson we cover the longest and most important job of all, cleaning the carburetors.
Cleaning the Weber Carburetor
If you have not checked out our Carburetor Teardown, please catch up. After teardown, you should have two carburetor bodies with no parts inside.
Using a chemical dip is not really effective when working with an old and corroded carburetor. For us, carburetor cleaning is best achieved by blasting. Water or vapor blasting is the best, but all blasting has its pluses and its drawbacks.
You need to use the correct materials and techniques when blasting so you do not damage your carburetor bodies. Many of you will stop right here and say that you can never remove all the blast media. This may be true if you do not refer back to our number one tip, Gallery Plug Removal!
Please note, we have left our studs in place for easy blasting. We will remove them after cleaning and before the carburetor bodies are sent out for color.
Removing the Gallery Plugs
The fuel travels through the carburetor passageways and they can become blocked with corrosion and old fuel.
We use a 2.5mm drill bit to drill into the soft lead plug by hand. We pull all the lead plugs from the front and top. The brass plugs on the side passageways are generally ok to leave and only need to be pulled on very corroded sets.
Be careful when drilling and prying out the lead plugs. We will not be putting the plugs back in until after the coloration process. Catch this process in Reassembly Part One.
Cleaning the Cast Zinc Parts
In our first lesson, we separated our carburetor parts into like materials piles. The accelerator pump housings and covers, the auxiliary venturies, plus the accelerator pump nozzles, are made of cast zinc. We clean these parts in the vapor blaster, and then they go in the ceramic polisher. Blasting opens the pores and polishing closes the pores in the metal.
We wire these parts together to make it easier to blast them. They stay wired in the ceramic polisher to not lose them.
Cleaning the Brass Parts
Over the years we have tried many different methods for cleaning brass. We have moved to wet polishing as opposed to dry polishing years ago. The wet formula for the tumbler is water, stainless-steel bits, Lemi Shine, and dawn dish soap.
The steel media is very small, and caution has to be taken with the accelerator pump jets, and other holes. A check valve has a hole that somehow the steel pieces vibrate into. We do not have to wire the small brass parts together, as you can just use a tumbler separator or a magnet to remove the brass from the polishing bath.
Our Brass Cleaning Set Up
The brass will need to tumble for an hour to two. Do not over tumble as the threads on the brass parts can become damaged. If you do damage the threads, you can chase them with dies and taps.
How to Clean and Test the floats
When it comes to cleaning the carburetor floats you cannot blast them. The brass floats are quite fragile and may already have damage. Well-meaning people that squirt compressed air down the vent tubes, hoping to unblock a needle and seat, are responsible for many a crushed float.
To clean the floats, use Dawn dish soap and water with a Scotch-Bright pad to gently scrub and polish the floats. You can see if they are useable during this cleaning, if they bubble when underwater, they are out. Another way to check the floats is to weigh them.
Floats have the weight stamped on them, 25.5 grams. They should weigh one gram on either side to be useable. The new solid floats are a little lighter and may behave a little slower in the carburetor, but they are a great replacement for a damaged brass float.
We replace all brass floats to be on the safe side. Brass ages, and floats age too, repairing a seam can add too much weight to the float. Nine times out of 10 we replace.
Carburetor Chokes and cleaning them
Carburetor chokes are a cast aluminum. The aluminum can have air pockets already in them from casting. Blasting can blow up these inconsistencies like blisters. You must take more care and more distance with the blast nozzle when blasting the chokes.
If you have a modified choke, you need to inspect how it was done. If there is a large flat surface area inside the choke don’t bother cleaning it. You will need to replace a choke that has been incorrectly modified. The choke is measured at the smallest part across.
After blasting the chokes are added to the ceramic polisher.
Steel Parts
Steel parts have plating for a reason. The reason is not just for looks. Even though re-plated parts look fantastic, the plating is there to protect from corrosion. If you just blast your steel parts and put them back into use, they will rust in a very short time.
We replace a lot of steel parts as a matter of fact, like all the washers and nuts. Special parts like the arms, pump lever, pivot screws, and choke holding screws can be sent to re-plate. Unless you have a lot of other parts to send to replate, it may be more economical to just buy new parts. Re-plating used to be a lot cheaper, but with the pressures on platers, the cost has gone up.
Vapor Blasting your Weber Carburetor
In our Vapor blaster, we use a fine glass bead. Do not use aluminum oxide, it is too aggressive for the Weber carburetor. Take care even with a gentler glass bead. Do not blast too close to the gasket surfaces.
It will take time in the blaster to get all the nooks and crannies. Keep at it, and make sure you rinse well. Even though this is not the final clean, you do not want media drying in the passageways.
Throttle Shafts
We start the carburetor inspection with our throttle shafts. Weber three-barrel carburetors have an 8mm throttle shaft. Discard a shaft that measures at 7.95mm or less or if it has heavy scoring. The Teflon bushing helps to preserve the throttle shafts.
On this set, the short shafts were both usable. We replace the long shafts. Mostly it is the throttle shaft that wears, not the carburetor body. If you have damage to the body you can oversize the throttle shaft and ream the body to suit the new shaft.
Complete any machine work on the carburetor bodies before color. There is an exception for thread repairs. If you time sert with a steel insert, it will not survive the coloration process.
Measuring the Jets
Taking the time to inspect the brass jetting is essential. Pin fitting the jets will let you know if the jets are the size they are marked. The jetting must also be the same size as each other. If there is any inconsistencies, or the jet is damaged, it is better to replace the jet.
Just like the choke, drilling jet changes how the jet flows. So if you find a drilled jet, change it for a new jet.
Tools used in this tutorial
From drilling the galleries to checking the throttle shafts and carburetor bodies, we use a wide range of tools.
Up Next, Putting your Carburetor back together.
It was a lot of work to clean and measure the weber three-barrel carburetor. Now the bodies head out for color and we get our new parts together. Next up is the re-assembly and we start with the gallery plugs we removed and the throttle plates.
For our series the reassembly is three lessons.
1 thought on “The Most Important Part, Cleaning Your Weber Three-Barrel Carburetor.”
Curt this is Steve Miller. I did some business with you when you were at ParrtsKlassic. Mike gave me your info. I have a particular problem with some Webers on a 3.0 liter that I put in my outlaw. I ordered one of PartsKlassic’s Jet Package kits as well as other parts. The car seems to run out of fuel at the higher RPMs..and I have gone up and down the gambit with jetting. Also replaced the MSD box and coil and am about o=to install the clewett ignition wire set.
I took some webers off another car (914-6) and there was vast improvement but not 100% performance. There were some jetting and venturi size differences between the two sets of carbs and the jet performance kit seems to have what I need. I was wondering if I could set up a call with you and just pick your brain on my options. Thank you in advance if you can do that. Looking forward to hearing from you.
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