5 Things That Make Living with a Carburetor Easier
A properly running car is a finely tuned system of parts working in harmony. Any component, then, can make the difference between a running and driving machine and a coughing, spitting garage ornament. If one critical component is a bit persnickety, it often earns a bad reputation it may not deserve. If you know (or are) someone who’s into old cars, you probably know the love/hate affair with carburetors.
We all know the holy trinity of engine worship: Fuel, air, and spark. These three elements must exist in the right proportions for an engine to run. Because “holy quaternary” just doesn’t have the same ring to it, compression gets shoved off into the corner, to be discussed only by those who have ascended to a higher tier of diagnostics beliefs, like that guy with the long beard who is still remarkably adept at spark plug reading. He diagnosed a distributor gasket leak from across the parking lot once. I was there.
Maybe I’m misremembering, but it’s precisely that kind of guru mechanic people picture when want someone to work on their carburetor. It doesn’t take a wizard to have a great-running carbureted car, however. Just about anyone can have it. To get there and stay there takes a little bit of care, but the basics boil down to five things.
Use Clean, Non-Ethanol Fuel
Although ethanol-blended fuel does have big power potential, it is also the root of more than a few headaches for those of us with a vintage bent. Gasoline will evaporate at the temperatures most of us like to cruise in, and that means the gasoline disappears and leaves the residue of the ethanol behind. It clogs the multitude of precision passages that make a carburetor function. Most carb tuning and advice is rooted in pre-ethanol times, so even using jetting and setup advice can be tough, as ethanol fuel behaves differently compared to “pure” gasoline.
A Well-Tuned Choke
Listen to the arguments against carbs, and cold starts are oft cited as being a runaway victory for fuel injection. It’s a fair point; fuel injection has won the smooth-running game handily, but a well-tuned choke on a carb works really well considering how simple it is. After all, it carried us through when our hobby cars were simply daily drivers.
Thermostatic chokes often use a bimetallic coil, which is just two different metals bonded together that expand differently when heated or cooled. Pump the throttle once before starting the engine to set the choke, and the engine should start and set at a high idle. Consult your shop manual to get exact settings. Tuning a choke can be finicky, but when it’s all sorted, there is nothing quite like a smooth start-up on a crisp fall morning.
Happy Distributor
A professor of mine from college once told me “90 percent of your fuel problems are ignition.” People will be chasing “carb problems” for hours before realizing the damp spark plug that seems to be running too rich is actually just a plug getting weak spark or not firing at all. Keeping the ignition in top shape helps to keep many other components running smoothly—and it also assists with diagnostics for rough running.
Smooth Linkages
Binding linkages can make chokes stick and accelerator pumps function inconsistently. It’s wild to think that the carb’s exterior cleanliness is just as critical as its cleanliness inside. Road grime is attracted to oily or damp surfaces, and it only takes a small amount of oil mist from an open breather or leaky gasket to attract a surprising amount of junk, which will damage small seals or gum up finicky linkages.
Clean Air
It seems there are actually three sides to a carburetor: the fuel side, the air side, and the outside. Does that make sense? Maybe. Regardless, the air coming into an engine is the easiest pathway for all the stuff that should stay outside of an engine to get inside of it. Dirty throttle blades and intake manifolds can cause interesting problems in both carbureted and fuel-injected engines. All the delicate and small air passages that help keep carbs balanced and flowing can get clogged quickly. Keep an air filter on the intake, and your carb will be happy for a long time.
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A pair of 40DCOE Webbers on my IWR Lotus Cortina. Life was good 👍
Here in Miami, boat and jet ski people have provided plenty of business for REC 90 gasoline. It’s 90 Octane pure gas available at Marathon and Exxon stations along the routes down to the water. Motorcycle engines also love that gas. I use it in my old GMC with 4 BBL Quadrajet Rochester on the 350 V8. By the way there’s a website called pure-gas.org – they currently have 16,933 stations across the country with Ethanol free gas. Also don’t forget your chainsaw and lawn mowers..my yard guy complained to me about the high cost of having his gear fixed until I told him to get REC 90.
My car came with a Fuel Safe fuel cell from the factory. I’d love to know if ethanol causes the Kevlar bladder or open-cell foam inside to deteriorate faster. I’ve had to remove the cell and send it to Fuel Safe to have everything inside replaced (over $3 grand) because it started leaking. I see on the pure-gas.com site that there’s a station not too far from where I live that has ethanol free gas. It would be worth driving there to save my fuel cell.
If anyone knows please comment.
I use ethanol free gas in my Model A, not because I’m afraid of ethanol but because it might take 2-3 weeks to use up the gas in the tank. In that time, the ethanol will absorb moisture and the inherent corrosiveness of alcohol along with the moisture will begin to gum up the works.
Landscapers in our area frequent the non-ethanol pumps because of the tendency of mowers to be exposed to more moisture and maybe they have older rubber/plastic tubing that can’t handle the ethanol.
In terms of pure power (racing), ethanol doesn’t have the same power potential as gasoline, so you’re down on power simply by using E10. As the ethanol in the fuel absorbs moisture, it loses more potential energy. If you want max power out of your carb, you need to use pure gasoline. This also explains why you get better gas mileage with pure gas, as it has more power potential and hence you’ll use less fuel to get where you’re going, compared with E10 (or E85, if you’re a flex fuel vehicle).
As they say, it’s complicated…
If you have carburetors, you’ll love an ultrasonic cleaner. (Sure beats the old way.)
On small engines, I always shut off the gas and run them dry when the job is done. Saves a lot of trouble.
SeaFoam. One oz per gallon of brand name fuel.
Anything I have that’s old and doesn’t run everyday gets nothing but treated fuel. Ever. Generators, mowers, boats, motorbikes. Doesn’t matter how the fuel is delivered. Acts as a fuel stabilizer too without the goo that comes with the Stabil crap.
IMHO, the whole point of having a special car, or any car, is to drive it, show it off a little, and fish for those illusive, “Nice car” comments from people on the street. I mean, why else do we spend years fixing up a money pit? Remember, your dream about that car was to go out and cruise around and show it off, not stand in the driveway polishing it. If a car is going to actually be driven, it needs to run on commonly available fuels. That means Ethanol. Replace the mechanical fuel pump with an electric at the tank and a pressure regulator at the carb, that way the fuel line is under pressure and not as prone to boil. Make sure the rubber is all Ethanol proof and then get out on the highway and drive it. Go to the beach, up to the mountains, to the lake, or to the desert, like you used to do. Those fun trips almost always involve a stop at a gas station, which is also an excelent place to reel in the “Nice car” comments. A good short trip is usually good for four or five Nice car’s and those are much more rewarding than “I have one of those in my garage”. If it requires special fuel, it’s not practical to drive anywhere except within a range of half a tank. That’s called a trailer queen. Again, IMHO
I solved my Quadra-jet issues, by donating the car to a local radio-station.
My 1964 Mk2 3.4L Jaguar has 2 x SU carbs, and a fuel enrichment solenoid (like a choke) that allows vast amounts of fuel into the engine. I had to leave it stored somewhere for 63 days, untouched. Came back to it, once we had moved, switched on the ignition and waited until the fuel pump filled the bowls, ‘Tig tig tig tig tig’. Pressed the starter and it fired up first time and ran on choke until it warmed up and I cut the choke. That is a 60 year old car, original engine and carbs, with CB points and a Lucas coil. I agree, there is nothing wrong with carburettors as long as they are set right and the fuel filter gets changed regularly.
If you live anywhere near a marina or a boat launch, high octane non-ethanol fuel should not be difficult to find. Can be expensive but well worth it. Ethanol fuel works fine in a carburetor as long as the car doesn’t sit. Six to eight months of non-use over the winter can cause lots of corrosion and other issues with ethanol based fuel.
Fuel -check Air – check Spark – check Compression – check……..AND they all have to get there at the same TIME!
Many choke problems in later carbs are caused by a bad choke pulloff. Especially quadrajets. If the pull off fails the choke won’t open enough on start up to run properly. Easy to check. Cheap to fix.
Ethanol is alcohol which collects moisture in carburetor’s and fuel systems..I have been a motorcycle, small engine, large engine mechanic for over 50 years. I see what ethanol gas does and i make my living off the green stuff that coats the inside of the carbs, and cleaning out the rust from gas tanks..I run non ethanol in my motorized toys and have had no issues. If you have to run Ethanol gas, use a fuel treatment purchased at any parts store..
Do you think I should try to get the rust out of my Suzuki 400 Enduro (2 stroke, single cylinder, late 70’s) gas tank or use a plastic tank that I have and will fit? I had no idea that rust would form as the motorcycle sat for years. I had run the carb dry and shut off the fuel. I live in MO.
Unfortunately moisture is a pesky bugger when it comes to infiltrating areas you don’t want it to. Good practice is store with a full tank or fog the inside with a light coating of oil for long term storage. Anyways, you absolutely should clean it and it is an operation most owners can DIY. There are tons of different ways to get rust out of a tank. I think that for an older bike, the original tank is usually the way to go. You’d be surprised how bad of a tank can still be saved.
I DIY’d a tank cleaning on an early 70s Yamaha AT1 that turned out well. Filled to the top with vinegar and agitated with a small handful of hardware store nuts. Couple days of sitting and it came out pretty clean.
I recently saw a video where a guy used Evapo Rust and let it sit and the tank looked amazing after.
I once put a bunch of washers and some Kroil into an old rusty motorcycle tank and fitted it onto a homemade (Rube Goldberg style) lathe – a small electric motor salvaged from a desk fan ran it. After a couple of (very noisy) days of tumbling, the tank rinsed out about 95% rust free.
I finally figured out how to fix my leaky smelly stumbling forever out of tune Holley carburetor. I carefully removed it, dumped out the remaining gas that hadn’t leaked out and put it on the shelf and installed an EFI system. Problem solved. It made a whole new car out of the 64.
Ur articles are informative and interesting to read . Thank you for another entertaining stimulus.