A line of 1923 Center Door Sedans come from the upholstery area towards the final assembly line in the Highland Park Plant. Photograph dated April 2, 1923 property of the Henry Ford Museum collection. About half of these cars would be equipped with Kingston L4 carburetors when they left the plant.
Kingston introduced the final variant of it’s L series carburetor for the Model T Ford at the beginning of the 1922 model year. It was the iconic Kingston L4, used on millions of Model T’s and TT trucks from 1922 – 1927. A good performing carburetor, it provided years of trouble free motoring and simple design that could be repaired easily. Let’s take a look at how to restore one.
Our subject came to us in a box of miscellaneous carburetors bought three for $20 on eBay. From this side we can see it is surface rusted but not too bad really. The flapper pivot is missing, as is the flapper itself. A look at the other side reveals more missing parts, including the bowl drain stopper, the throttle arm, and the fuel inlet fitting. This one can be dated to 1923 – early 1925 due to its cast iron body and the mixture control that fits all Model T’s made from 1909 – early 1925. The earliest L4’s built in 1922 had a bronze body. Also the earliest Kingston L4 carburetors used a cork float, replaced by a more sturdy brass float within a year of introduction. We buy some carburetors for parts, and so we had to scrounge these items from our spare parts collection. Clockwise from top left are the flapper hinge pin, Kingston Fuel Cleaner inlet fitting (aftermarket, with built in filter screen), float bowl drain stopper, throttle arm and shaft, and flapper air valve. While taking the carburetor apart we ran into a super stuck flapper valve stop screw. We heated the area around the screw to a dull red using the mapgas torch. Then we let it cool for 30 minutes and applied penetrating oil. The stop screw came out easily. The L4 disassembled so we can examine the parts. Amazingly, this carburetor has what looks like a brand new float, needle and seat. The choke spring is broken and will need to be replaced with a new one from Lang’s. We put the brass parts into the Berryman’s Chem – Dip can. The steel and iron parts go in the Evaporust pan. Everything soaks overnight. The next morning our carburetor parts get a hot water bath and a little scrubbing with scotchbrite. Our parts are starting to look pretty good. We clean the steel and iron parts using a fiberglass round brush in a high speed motor. We sprayed the internal passageways with Berryman’s B12 carb spray, then dried everything with compressed air. Our replacement throttle arm has no holes for the retaining staple. We sprayed it with some flat black primer so that scribe marks would show well, marked the hole locations, and drilled them with a #62 AWG drill. A little masking and everything is ready for the primer coat. We always like to re – use the original patent plates if possible. This one was nice so we masked it off and cut around the outside with an X-acto knife. We polished a few parts that show using the buffing wheel and jeweler’s rouge. We made a new bowl gasket from .030″ gasket paper. A Kleenex box can be used if you are really on a budget. We made a new gasket for the bowl nut too. First we punch it out using the 1″ leather punch. Then a 1/2″ punch makes the center hole. We placed the flapper air valve in the carburetor to start the reassembly process. Next we installed the flapper air valve’s pivot. While tightening this slowly we made sure the air valve still moves freely. As we tightened the screw the air valve locked up long before the screw was tight. We ended up having to carefully file both sides of the air valve hinge until the screw could be fully tightened without locking up the valve. The stop screw goes in next. To check flapper movement just look in the front of the carburetor. With the carburetor level the flapper is laying at the base of the intake, as it would be at idle. Then turn the carburetor upside down. The flapper air valve should easily fall against the stop screw as shown. The flapper would be in this position at high engine speed, air pressure would hold the valve wide open. The inlet needle seat goes in with a new gasket. After the seat is tight the needle gets dropped in place. The float and its hinge pin come next. With the float installed we use needle nose pliers to bend the tab at the inlet needle to achieve 11/32″ float level, measured at 180 degrees from the hinge. We install the bowl gasket, bowl and the gasket below the nut, then snug the nut. You can buy new staples, or make your own from .043″ stainless wire. I copied one of the originals to make new ones. The choke and throttle blades are held in place with our newly made staples. And then bent over with needle nose pliers. The last thing we do is screw in the inlet filter. We do not use any thread compound or tape, generally none is needed. If we have a leak later on we might use some Permatex #1. Our Kingston L4 is now ready for decades of trouble free driving. 1924 Blish Mize & Silliman Hardware Company Catalog shows the L4 equipped with the Kingston Fuel Cleaner as one of many variations available to the thrifty Model T owner.
The Kingston L4 was used in Model T Fords from 1922 – 26, and in the TT truck from 1922 – 27. Here are some variations that are commonly seen.
In 1925 model year the mixture and choke linkage was improved. Carburetors made during this period received a mixture needle equipped with a universal joint as seen here. Float bowls on later carbs have no drain and are sometimes manufactured from cast zinc. Notice the variations in the float bowl and the float bowl nut size. The center L4 carburetor is probably from 1925, it has a steel nut that is much larger than the 1923 – 24 L4 carburetor on the right. The 1926 L4 carburetor on the left has the same size nut as 1925, but now the nut is made from brass, and there is no drain on the float bowl.