Rebuilding Your Carburetor is No Big Deal, Really!

By July 2, 2014Engine, Fuel
How to Rebuild a Carburetor

Even though a carburetor is made up of intricate moving parts, you don’t have to be an experienced mechanic to take it apart, clean it, and reassemble it. If your car or truck is slow to start, hesitates during acceleration, has flat spots while driving, stalls, floods or goes through too much gas, it may be time to get your hands dirty. And, it really isn’t all that hard, even if you’ve never done it before, really!

What you’ll find is that the toughest part of a carb rebuild is just keeping track of all your parts and making sure you put it back together in the right order. There are many small parts that can get misplaced or fly off so I recommend that you set a few hours aside to do it without interruptions, keep an organized work area and use a camera to take reference pictures for every step. A carburetor can last for the life-time of your vehicle with periodic rebuilds so it’s a valuable skill to master.

TOOLS

  • Wrenches – open and box end (usually 1/2-inch)
  • Socket and ratchet (again, usually 1/2-inch)
  • Screwdrivers – Philips, plain, and maybe Torx (T-10 or T-15)
  • Long nose pliers
  • Adjustable wrench
  • Carburetor rebuild kit
  • Carb and choke cleaner spray
  • Can/bucket of carburetor cleaner (Berryman’s or Chemtool)
  • Shallow plastic or rubber bins for soaking parts
  • CLEAN rags & new toothbrush
  • 3-inch piece of 1/2-inch tubing with a bolt in one end
  • Small parts container(s)
  • Camera (good if it’s your first time)
  • Rubber gloves and safety glasses

1. Determine What Carburetor You Have and Get Parts

Carburetors on most older cars and trucks were made by either Rochester or Holley, however some had Carter carbs. Usually the brand will be stamped or embossed on the side. Remove the air cleaner assembly and set it aside. Look on the front of the air horn (where the air goes in) for some numbers. You’re looking for something like 8514, 8150, 8154, etc. The string may be alphanumeric and longer than four characters, too. Write this down and either get online or trundle down to the parts store to get the rebuild kit and parts you need.

Rebuild or “renew” kits make reviving your carb a breeze because they come with everything you’ll need including gaskets, power valves and other replacement parts that are commonly subject to wear and tear. Be sure to get the specific kit to match your carb.

2. Remove the Carburetor

Take a few pictures of the carburetor how it sits before doing anything. Remove the fuel line from the carburetor inlet and cap it with the 1/2-inch tubing with the bolt in the end to keep fuel from spilling. Remove the lock clips from the accelerator and kick down linkages/cables and set them out of the way. Label and remove any electrical connections and vacuum lines. Loosen and remove the four nuts securing the carb to the intake. Place the nuts and linkage clips into the parts container for safe keeping. Lift the carburetor off the intake manifold and drain any remaining fuel inside.

3. Disassemble the Carburetor

Exactly how to do this depends on what kind of carb you’ve got, but the basics are the same. If you’re not familiar with the parts you’re taking off a good idea is to lay out each one in the order of disassembly on your table.

Remove the screws holding the float bowl(s) onto the main carburetor body. When you pull the float bowl apart, shake the float assembly to see if it’s fuel loaded. If it is, you’ll need a new one because it’s developed a leak in its air chamber. A float with fuel in it will be heavier than normal, causing fuel to flow constantly. You will also be most likely separating metering plates from the carburetor body. Loosen the screws without removing them and take a few pictures from all angles. On some carburetors, you’ll also be removing the throttle plate as well. Most carburetors will also be equipped with a power or accelerator pump/valve on the bottom of the carburetor. This comes off also, but be careful; there’s a small check valve in them to keep fuel from flowing backwards. It’s a small, small ball bearing, maybe with a spring.

As you begin to accumulate parts on your table you’ll notice that although some are very similar in appearance, they are not interchangeable so take lots of pictures to guide your through the reassembly.

4. Clean the Remaining Pieces

As gasoline gets old and evaporates it leaves behind a gummy varnish on the inner surfaces and small orifices of your carburetor. This and small particles can plug up small passages that meter air or prevent parts from moving as precisely as they should.

There are a variety of cleaners especially made for carburetors including baths and sprays. Although baths are slightly more expensive, they’re extremely efficient and will have your parts clean in no time. But sprays are great for flushing out crevices and small pathways in your carb so it’s best to have both at hand.

Liberally spray or place in the bath all the parts that you’ll be keeping with the carb and choke cleaner – minus the rubber parts, electrical components, gaskets or plastic. If using a bath, double check that it’s “alumunim safe” before throwing your base plate in there because long-term exposure to some of the harsh solvents will corrode aluminum. There are some orifices and internal pathways in the main body that you’ll need to carefully spray out with the carb and choke cleaner spray. Hold the carb well away from your body and face as you do this and wear glasses.

Let the parts soak in the bath or let the spray penetrate for about 10 or 15 minutes. Once well soaked, scrub them with the toothbrush. Some people use a wire brush but if you rub too hard the more delicate parts can get damaged. Spray them again to remove as much of the gunk as possible. Make sure that the mating surfaces where parts come together are all pristine, otherwise they’ll leak. A little 500-grit sandpaper works great. Rinse off all the parts with water and let them dry thoroughly. Compressed air or an air hose comes in handy for blowing out all the water in the small passages.

5. Reassemble

Open the rebuild kit box and confirm it’s the correct one because many stores won’t take it back once you’ve opened any of the parts. The first thing you’ll notice is that there are more gaskets than you originally removed. Don’t worry, this is to cover the different configurations in which your carburetor was manufactured. Match up the new parts you find inside with the old parts from your carb.

Your rebuild kit will have detailed instructions and diagrams to guide you. Put parts back on in the reverse order they came off while replacing each used part with its corresponding new one from the kit. Refer to your pictures often and don’t forget the carb baseplate gasket!

Although your instructions will help you make the necessary adjustments, you’ll need to fine tune the air-fuel mixture and the idle speed after reinstalling the carburetor and hooking everything back up. We’ll cover that in the next article but even now you’ll notice that your motor immediately sounds better.

Notes & Safety
  • Only do this in a very well-lighted and well-ventilated area. And, no smoking while doing it. The chemicals you’ll be using are toxic and explosive.
  • Carburetor cleaners have aggressive chemicals. Protect your eyes and hands by wearing safety glasses and rubber gloves.
  • Never probe into the small orifices with drill bits or paper clips. They are engineered to be a specific size and shape. If you need to clear a passage way, use fishing line.
  • Inspect the base plate to ensure it isn’t warped from a thick gasket or heat spacer. If so, lay a sheet of 320-grit sandpaper to a flat pane of glass or other flat surface and then hand-sand the bottom of the carb before reassembling.
  • No matter how good your old parts look after cleaning them, always use the new ones from your kit. Springs lose tension, valves distort, and gaskets become weak in certain spots over time.
  • When reassembling and re-installing the carburetor, tighten screws opposite from each other to evenly distribute pressure turning them a bit at a time so it takes about 3 passes to fully tighten each one.

Photo credit: Ryan Frost

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