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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Some of us have no choice but to use gasoline violated with a load of ethanol. The problems this creates include “phase separation” (look it up) and go on with, rust in every metal part of the system, rubber failure of hoses, needle valves, regulators, fuel pump diaphragms and gaskets. Engine will run hotter and don’t forget the vapor lock! And the problems with this nasty gas sitting in your system over periods of storage. I try to keep my tank full and add a surfactant to reduce air and condensation out of the tank.
The first pic looks like a motorcycle carb. Really? Was that the best you could find?
I have forgotten more than most know about Carburators, and that’s fact, not bragging. I can take apart and reassemble Holleys and Quadrajets in my sleep. It isn’t magic, but people these days make it sound like witchcraft. Just learn what works and what doesn’t. I’d rather have a good running carbureted car than any fuel injected setup there is. And if it isn’t running good, I’ll make it run good, or die trying.
On cars and other engines (lawn mowers, other yard tools and 4 wheelers) that don’t get run regularly, ethanol is not good for the carb. I have had to replace the carb on my 4 wheeler, and have several yard tools that I now have to either rebuild or replace the carbs. It hardens the gaskets, and messes up the floats.
Not every manufacturer is fuel injected… the brand new Honda 150 street and trails still have finicky carbs…. hate the cold they do! Full choke and wind over for 5 seconds, half choke and wind over until they, sometimes, start then do not touch the throttle for a minute! Although brand new ’24s, they start the same as the five year older versions… meanwhile the injected ones start right up….plus side …. so easy to diagnose and fix…mixed emotions lol
For gas treatment I use ethanol shield you can get it at TSC. I bought a new. Chain saw 15 years ago and dealer told me to use it in my gas been using it in all of weed wackers leaf blowers and generator witch sets a lot and in my 65 Rambler and other vehicles and to this date I have not had any carb problems with ethanol gas. Also it is good if the gas sit for a period of time such as over winter. For me it is better than stabil by a long shot. Something else you guys with old cars have any of you ever put 2 cycle oil in gas? Back when ethanol gas showed it ugly head an old time chain saw repairman told me to put 2 cycle oil in gas for my car he said it helped lubricate the upper end of the engine I did it and did not ever have any problems with performance. Any body else ever heard of doing that?
You reminded me, Yes i used to put light oil in the Ethanol as I pumped at a station..I used Marvel Mystery oil made by Lucas. It did work pretty well and kept the Carb lubed and clean to a degree. Then I discovered that REC 90 Gasoline was offered at a few stations so I kept the Marvel oil for all my other tools and gear.
Engines START on the accelerator pump shot, that’s why a COLD motor needs a couple of pumps. The choke just has to keep it running until it warms up.
As a drive ability tech at a dealership from the mid 70’s to the mid 80’s I found many carb problems were a direct result of improper adjustment. If you rebuilding a carb go thru the adjustment procedure carefully and accurately. If the intake manifold has a internal heat cross over check it, they will plug and cause several issues. As does a failed heat riser. If your installing a after market carb from any source check the jetting. Nearly everyone I installed ran rich. A 14.4 to 1 fuel ratio is ideal at all load ranges. Carefully adjust the fuel mixture to best idle. A trick that works well is removing a vacuum line. If the engine idle increases its to rich. If it goes slightly rough your adjustment is correct. also check for vacuum leaks at the intake manifold runners, carb base gasket, and vacuum lines. A little carb spray along those areas will tell you if any leaks exist. If your still running an EGR valve make sure it closes at idle. End of class for today. Lol
Now I know I’m old. My first car had a manual choke. The second had a grungy 2bbl Motocraft carb atop a 302 Ford circa 1975. I just purchased a rebuild kit and tore it down. Even pre-internet it went back together quite easily and all worked better in the end. It’s fuel injection that seems complicated to me. Not to mention the carbs were mechanical and easy enough to diagnose. Only my friend who owned an MGB has some issues sorting out carbs. Even he overcame the issues of speaking Canadian and not British…
Amen!
The Autolite 2100 and 4100, as well as the subsequent Motorcraft 2150 model Carburetors are about as simple and reliable as you can get. Although I hesitate to proclaim the same enthusiasm for internet available mass-‘overhauled’ offerings, where calibrations may be out-of-whack, due to the mixing / matching of internal parts.
Fuel Injection has the advantage of improved mixture distribution, but also relies on Sensors, some sort of Controller and multiple other components to accomplish that feat. Too much complexity increases the opportunity for higher repair costs.
Kados to Kyle Smith!! Looks like he hit a home run with this one!! Most enjoyed the comments!! Many of my experiences revealed!! My very first carburetor experience was converting my model A from an “up draft” to a “down draft” carb. All I know is Ethanol Fuel is B.S. Cheers!!
dirty throttle blades and intake manifold ??? ,, ie dirty throttle plates and intake manifold runners are only a problem on port or direct injection ,,, on a carbureted engine the raw fuel crosses over the throttle plate area and through the intake manifold runners which keeps things clean
Interesting, I have 20 vintage vehicles, all but 3 have carburetors . My oldest is a 37 Chev (original 216 engine) my latest are 6 68 Oldsmobile Toronados all original as well as carburetored boat engines). I have had no trouble with ethanol as I mix my own fuels and have for years, since that ethanol has terrorized out vintage vehicles.
One pint of no.2 diesel to 10 gallons of any modern gasoline takes care of all ethanol problems. I live in very rural America.
Did anyone mention adding an electric fuel pump to help alleviate vapor lock/fuel boiling?
Back in the day I had a Triumph TR6 and I was concerned about the modern fuels, my local British Car Mechanic told me to use Marvel Mystery Oil in every tank and I would have no worries. I used it in a couple of TR6s through the years and now in a 69 Vette and all of my small engines and never had an issue with fuel or gumming up a carb. I am curious if anyone else has has similar experiences.
The article says “Although ethanol-blended fuel does have big power potential…”. Nonsense. Ethanol has less chemical/thermal energy than gasoline. Just chemistry–look it up. Gasoline is about 125,000BTU/gal, Ethanol is about 75,000BTU/gal. The only reason to buy ethanol-blended fuel is because it isn’t as expensive, and you can find it everywhere.
Hi Robert,
Higher-percentage ethanol blends are regularly used to boost horsepower significantly, especially on tuned, boosted cars. The tuning/timing principles are a bit different—as you mention the potential energy is less—but all other things being equal, a boosted car running 93-octane and a tune will generally make less power than a ethanol blend and an appropriate tune. It’s even more pronounced with fuel mods to accommodate a higher-ethanol blend.
E85 has a very high octane rating. Turbocharged cars can run a lot more boost with E85 vs pump gasoline before detonating. As you mentioned, energy density of E85 is a lot less, so 30% more fuel is needed, but this has the added benefit of cooling the air from the increased latent heat of vaporization. E85 is a whole lot cheaper than 110 octane race gas and has no lead