Topic: Ford 2100/4100 Carburetor Body & Cover Cleaning

[Dan Case]

Cleaning 2100/4100 carburetor bodies and covers without permanent surface changes.

Most people will realize that as die cast aluminum surfaces get modified permanently if any hard media blasting, tumbling with media polishing, wire brushing, or vibration with any kind of media polishing gets done. Strong mineral acids and strong bases can etch away aluminum too. 

It takes a lot of time and steps but I like to clean bare aluminum carburetor castings without any of the methods above.  I would really like to try dry ice blasting to deep clean the original surfaces but so far I have not found a shop anywhere close to discuss such work with.

In the mean time I thought I would show you some examples.

On the left below is a new old stock 1965 model year carburetor assembled in the summer of 1964. Ex-dealer stock somebody robbed it of parts long ago but it stayed very clean and all the factory paint and grease pencil markings are still present for parts still there. On the right below are a used body and cover for a C3OF-AJ carburetor I am working on for a friend. No, it is not possible to get just out of the mold appearances for old used aluminum parts but if no one has damaged them and they do not have corrosion from something like antifreeze/coolant they usually clean up pretty well.




The C4OF-AT carburetor below is not what I call a restoration. Cleaning removed all factory paint daubs and grease pencil marks so I did try to recreate all of them accurately. (The owner supplied the freshly replated air cleaner stud shown.)  I cleaned and serviced it for an old friend. The worst stain it has is a dark line across the choke plate from antifreeze/coolant corrosion.



My process set is a long one. I spent 9+ hours masking, cleaning, dealing with gasket flange burrs somebody created before I got it, testing all the threaded holes, testing relative flows through all calibrated orifices, and gently chemically cleaning all the brass orifices and tube bores the body and cover for the C3OF-AJ carburetor above.  (It is best to never run metal anything through calibrated fuel and air passages. The tiniest scratches or burrs can seriously affect in use air and fuel flows. Holley Carburetor Company use to give a document to racers that mentioned what their research results on damaged orifices were. I inspect every calibrated orifice under a very well lighted binocular microscope. Any removable orifices with any scratches or burrs go into the trash. Limited repairs can be made to orifices that do not come out or out easily. Vacuum pickup tubes in 4100 cover assemblies often need some amount of repair and often correction of angles and position relative to the auxiliary venturi to get in the factory specification location.)

Almost anything metal arriving at my work bench starts with a soak in WD40(R) lubricant for a day to two weeks depending on how soiled the assembly or part is and what the crud is.  Small parts get immersed and soaked in sealed containers. Large parts get sprayed and sealed in plastic bags.

4100 carburetor bodies and covers are reduced to everything that comes off without drilling, pulling, or pressing.  Electrical circuit cleaner is used to check that all passages are open and if applicable left and right side orifices appear to flow the same amounts. Disassembly is followed by a hot Dawn(R) detergent and water hand wash. After water rinsing at least three times, low pressure compressed air use speeds up complete drying while that parts are still warm.

The preparation for body and cover cleaning takes a long time. Every threaded hole gets something installed (old used parts I keep for the task, jets and valve body bores get sealed) to protect internal threads. Every soft aluminum and lead alloy core plug gets covered with four layers of thick aluminum foil adhesive tape rounds, the remaining small passages get multiple tape layer protection, and the fuel rail soft core plugs get an added electrical tape round covering each one of them. Tubes are covered with snug fitting rubber cap plugs. The vacuum secondary passages in the cover and body get sealed.

Once the body and cover are masked well used walnut shell pieces are utilized to medium air pressure media blast every surface they can get to on the body and cover.  New bare aluminum obtains a microscopic layer of aluminum oxide film just being exposed to air. Exposure to heat cycles and many chemicals accelerates and extends the oxidation process and over time the oxide layer not only gets a little thicker but it traps foreign materials like road dirt, oils, antifreeze, and residues from fuel allowed to get on the outside of carburetors. The dirty oxide layer is somewhat brittle and being very thin the walnut chips knock most of it off the parent aluminum underneath. I a twist of fate carburetors that got very dirty very quickly with oil, road dust, and or fuel stains in their service lives often have the most original looking surfaces once the crud gets removed.  Any oily fuel stained surface gets projected from further air exposure degradation.

After walnut shell blasting all the masking tapes, caps, and threaded devices are removed. The parts go to get hot detergent and water washed again.  The pressed in calibrated brass parts get cleaned chemically inside and out before final rinse and blow dry.   I get a liquid brass cleaner at the grocery store. If some trouble areas need scrubbing I do it with very fine bronze wool lubricated by soap and water.

Passages had liquids through them during testing and cleaning but before calling the bodies and covers done and ready for reassembly I use WD40 to verify all passages still flow as they should. 

How about the other parts? For just a service everything gets cleaned gently. Some defects can be repaired and some cannot. Most of the carburetors I service require some number of replacement parts.  My only way to come up with good used parts is to buy other cores made in the same time frame and render them down into small parts.  Like many other Ford parts and assemblies the parts carburetor bodies and small parts changed over time. Some parts were used only in certain time frames or certain carburetor assemblies in a time frame. Parts designs changed. Body castings changed. Platings and finishes changed. Even the stamps used to number carburetor bodies changed over time.  To return an unmolested carburetor to day one configuration is not difficult. Returning one that has been commercially redone can be quite a challenge.  One friend bought a "restored" 4100 carburetor from a world famous shop.  The body, cover, and throttle plates were correct for the carburetor assembly and assembly date but nothing else was. Every threaded part was either a reproduction or from some other carburetor. I kept the body, cover, and throttle plates but everything else was replaced with good original parts of the correct engineering numbers and time frame. Whew!

[KevinK]

Wow, nice write up. Just 1 question. I thought I read WD40 causes corrosion of aluminum? If I recall it resulted in scrapping several military helicopters.

[Dan Case]

Wow, nice write up. Just 1 question. I thought I read WD40 causes corrosion of aluminum? If I recall it resulted in scrapping several military helicopters.

I never heard that tale. The material was invented specifically for aerospace hardware.  It is mostly mineral spirits.  It does a decent job of sealing microscopic pores in sand cast aluminum and does dry to the touch. Being a mild solvent it does not instantly remove factory paint daubs and grease pencil marks like many solvent systems will. It is also relatively safe chemical vapor and flash point wise to use at a work bench with good personal protective equipment and ventilation.  Good nitrile work gloves lasts until a sharp edge cuts them. Anyway, I use it on some incredibly rare and valuable car parts and assemblies and have since about 1961.

My final bench test set  for carburetors is to live pressure test them between 4 psig and 6 psig. My filtered fluid for this testing is WD40(R).  I test for pressure decay of needle valves, check of leaks anywhere, and for Ford 4100 carburetors a do a STARTING POINT "wet" fuel level test and adjustment session. (Ford 2100/4100 models are to have final wet fuel levels set in their vehicle.)


Out of context that helicopter tale means nothing to me. I worked around the aerospace industry and friends of mine made parts for space craft and military aircraft. They made parts in titanium and other exotic alloys that got scrapped out if somebody even touched them bare handed before heat treatment was complete. My best friend made dozens of the external titanium alloy mounts to add bomb carriers to fighter planes for the Gulf War.  He spent a whole week cleaning his jig bore machine of any oils or foreign metals before the government inspector would allow him to start making parts.  After heat treating the contact restrictions got much less severe.

[CharlesTurner]

Based on videos I have seen of dry ice, I think that it mostly just cleans the surface, but have not tried it personally.  There is an entry level dry ice blasting unit that is $10k.  Then you have to buy the dry ice separately.

[Dan Case]

Based on videos I have seen of dry ice, I think that it mostly just cleans the surface, but have not tried it personally.  There is an entry level dry ice blasting unit that is $10k.  Then you have to buy the dry ice separately.

I bought an industrial sized system circa 1993 for work. Back then it was a six figure purchase. We ordered large containers of dry ice pellets to be delivered just before the work was scheduled. The change in technology saved hundreds of thousands of dollars a year in plant expense costs.  Converting from all manual scraping, sanding, replacing parts, wearing molds too far to reuse, and keeping polished tools repolished was a great time and money saver. We also did not have to keep as many spare mold parts on hand anymore as the damaged created by hand chipping, scraping, sanding, and constant handling  were eliminated.

Somebody in our aircraft engines business told me about the company making the equipment and its approved uses in aircraft engine maintenance.  I got somebody from the production department to go find a cast aluminum tool that was so fouled with baked on polyurethane they were discarding it, too fouled to save.  I sent the part to the dry ice blast equipment maker. It came back looking like it was just made except for marks were lock washers had cut in around mounting cap screws. I was sold and I sold the idea to our plant management.  What I do not know is how small machines perform. With the big ones air volume and pressure are the keys to how much cleaning is done. The pressure and air volume used determined how clean clean was when finished. Used lightly removing caked on grease and dirt could be done with no machine disassembly. Used at highest power baked on polyurethane, paint, or burnt on plastic came right off leaving intact original surfaces intact.

[RoyceP]

We always used walnut shells for blasting aircraft engine parts. It's slow and the media is useless after one use. I bet the dry ice machinery pays for itself by reducing man hours in the aircraft world, but it may not in the old car parts world.

[KevinK]

This was not the original conversation but the only one I could find. I thought the original conversation was posted on this site.

http://cr4.globalspec.com/thread/29944/WD-40-and-crack-propagation

[Bob Gaines]

This was not the original conversation but the only one I could find. I thought the original conversation was posted on this site.

http://cr4.globalspec.com/thread/29944/WD-40-and-crack-propagation

I have only heard of WD 40 being forbidden in shops because of the silicone content and ability to defuse in the air across a distance to cause fish eyes in freshly sprayed paint.

[Dan Case]

This was not the original conversation but the only one I could find. I thought the original conversation was posted on this site.
http://cr4.globalspec.com/thread/29944/WD-40-and-crack-propagation

Interesting link but to me the comments lack credibility.  They imply that some type of WD40(R) brand product, there are multiple products under the brand, is a stress corrosion cracking problem for some high stress components.  I did a beta type information hunt and found no specific case of the common spray lubricant I used being chemically the root cause of metal degradation. I found multiple examples of aircraft owners using it for all kinds of tasks on aircraft.  The maker provides products and spray cans specifically made to reach difficult locations during aircraft maintenance. Most  claims found, like claims that coating leading edges of wings to gain 2 knots more air speed are just ridiculous. The worst cases were owners washing grease out of moving element devices like rod ends and then having problems. The WD in WD40 means "water displacer" or something similar. It does not mean it is a good or long lasting lubricant. I use WD40 to gently degrease plain, roller, and ball bearings but I always removed the WD40 and reapply appropriate greases.   

My father was a metallurgist working in the space program from 1959. His lab had a hand in testing and developing alloys and joining processes for aircraft and space craft for many years including all the manned space flights before 1989, the titanium alloys for the SR71 and FA117 military planes, and he never gave me any warning about using WD40 on any metal alloy.  The day before he passed in 2003 NASA had a metallurgical question for him.

If one looks up the ingredients in the common WD40 product, they are all petroleum distillates except the carbon dioxide propellant.  My chemistry degree is decades ago now and I stopped being a practicing chemist and Fortune 500 manufacturing engineer in 2014 but there is nothing in the listed liquid component ingredients that are anything but oils and solvents. My  belief, if any of these cause problems with aluminum then any kind of "gasoline", kersosene, jet fuel mix, or mineral oils should not be allowed anywhere near aluminum.


64742-47-8. A high-purity mixture of hydrotreated isoparaffins and naphthenics with very low levels of polynuclear aromatics. It is an excellent process solvent with high flash point and narrow boiling range. It is also known as paraffinic naphthenic solvent. A major component of commercial kerosene and aviation JP-TS type aviation fuels.

64742-56-9. Distillates (petroleum), solvent-dewaxed light paraffinic.  Used as carrier fluids.

64742-65-0. Distillates (petroleum), solvent-dewaxed heavy paraffinic. Widely used in lubricant formulations, anti-freeze products, waxes, and polishes.

64742-53-6. Distillates (petroleum), hydrotreated light naphthenic. Widely used in lubricant formulations, anti-freeze products, waxes, and polishes.

64742-54-7. Distillates (petroleum), hydrotreated heavy paraffinic.  Hydraulic fluid.

64742-71-8. Paraffin oils (petroleum), catalytic dewaxed light.  Light base oil.

124-38-9. Carbon dioxide. Compressed gas propellant.

I find the common WD40 product useful in cleaning and that is about it. Any moving element device that requires a good lubricant gets something appropriate for the job. I have about six different oils, about five different "greases" for different applications, and two kinds of dry lubricants.

[Dan Case]

I have only heard of WD 40 being forbidden in shops because of the silicone content and ability to defuse in the air across a distance to cause fish eyes in freshly sprayed paint.

There are no mineral compounds listed in the MSDS or CAS number table. There are "waxy" materials in it though. In my beta research I came across many warnings that WD40(R) on any surface to be painted would result in "fish eyes" in the paint.  (Dawn(R) detergents are even worse because the do have silicon surfactants in them?that is what makes them work so well.)

[Dan Case]

We always used walnut shells for blasting aircraft engine parts. It's slow and the media is useless after one use. I bet the dry ice machinery pays for itself by reducing man hours in the aircraft world, but it may not in the old car parts world.

Some car restoration shops have started using dry ice blasting to gently clean undercarriages and engine bays before cars are dismantled and then using more aggressive dry ice blasting to clean subassemblies and parts.  A friend was responsible for getting a Boeing 747 repainted back about twenty years ago. Dry ice blasting was used to remove the old paint. It was costly but he said it was a fraction of the cost of doing it with chemical stripper and was safer for workers and the environment.

[Dan Case]

Back to the original program, I just wanted to share what has worked on Ford 4100 carburetors for me for years.  Holley(R) carburetor parts made of die cast zinc can be medium pressure walnut media blasted to clean the foreign materials layer off. If the parent zinc and dichromate conversion coating are in acceptable condition underneath the crud they normally come out looking good enough for anything but serious show car duty.


I am not suggesting that anybody has to follow my processes. Just sharing. I always try to preserve the original surfaces and finishes first  and have done so since 1961. That is not always possible.

During 2011 I cleaned up and serviced the induction system for a CSX31xx series 427 Cobra. The induction system was removed from the original engine in 1968 and placed on a shelf in a commercial shop. Circa 2005 it was rescued by the current owner of the car. It was a mess as it was covered with a heavy layer of shop grime and paint over spray dots. The owner wanted me to clean and service it to ready to use condition. He wanted no restoration.

One of the carburetors before and after my cleaning processes.
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The fully cleaned and serviced system. WD40(R) soaking two weeks, medium pressure walnut shell blasting, and the intake manifold got a final rinse with lacquer thinner out in the field behind the shop using a body paint spray gun from the 1960s. No parts were replated. No glass bead blasting. The heater shutoff valve is a new old stock one I found. The oil fill tube was badly banged up so I repaired it. The owner wanted it left bare steel until he painted the other engine parts at the same time so I did not paint the tube. The MS nuts and AN base fixing washers are new made reproductions of the 1960s versions of parts SA used. It came out okay I think and the owner loved the job I did.

[RoyceP]

Very impressive! I will try that in the near future.

[Dan Case]

Rework of a C3OF-AJ Revision Level A Dated 3LB carburetor.

I am a little further along with the current carburetor project.  Assembly and subsystem testing has started. The body and cover did not get as bright as I had hoped but except for being a little dark all the original casting and factory number stamp details are intact. All the used ancillary parts were sent out for plating work. I repaired the heads of every phillister head screw before replating.

[Dan Case]

I completed the current carburetor project. The aluminum castings turned out acceptably.