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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My idea of a successful “system” (of nearly ANY type) is based in simplicity. My days in vehicles began with manual chokes, and I’m stuck there even today. Pull a knob, which moves a cable, which closes the choke vane. Pushing the same knob reverses the process. Full analog control of what is happening, not having to rely on electronics or even something as complex as bimetallic coils. On the engines I’ve had with manual chokes, only a broken cable has failed me in 60 or so years.
There’s a duct system that directs exhaust heat to an automatic choke, often called a “stove.” When you improve your headers, you usually take this off and throw it away. Then your choke doesn’t want to unchoke. This is never an issue with a manual, unless you have a very poor memory.
Most engines won’t let you forget that they are choked as soon as they warm a bit. My Pontiac won’t hardly let me back it out of the garage after about 30-40 seconds of full choke. I’ve got to start backing the choke down (depending on weather and temperature) shortly after the engine firing. Although having said that, I have a 4-wheeler that runs best at half-choke no matter what I do! 😁
By chance is your 4 wheeler a Polaris 500? 😉
No, an old Yamaha Moto4 YFM225. I just use it to run out on the ranch to open and close gates, check on water, etc. Sometimes the grandkids ride it around a field, but even they are outgrowing it. It has yet to even be started this year – been too wet and cold here!
You most likely have a vacuum leak. Check the footgasket
I’m with you on this.
My top project at the moment is a 68 Travelall with a 304 which has both a manual choke as well as a manual throttle .Very nice to get going.
Oh yeah, love a manual throttle! I live on a ranch, and most of my farm equipment is equipped with both, like your Travelall. Good stuff.
Most people would do much better buying the right carb to start.
So many want a 750 double pumper. They want to pull it out of a box and just bolt it on a stock 350 Chevy.
Getting the right size carb is where you need to start. Then you need to set the float. Follow that with re jetting to get the right flow. Setting the idle and choke.
Most people screw this up only setting idle and fuel mixture. Then the car is still running rich. It may run better than the last carb but it is still not right.
No taking the carb apart is not going to void the warranty. It is expected. Yes buying and driving then trying to return a too large carb is not a warranty.
Yep, give me a properly tuned and operating Q-jet and life is good hot, cold, and when my foot is on the floor
Amen brother! The restored ’82 truck Q-jet on my 427 ’68 C10 runs great. Tuned for altitude (Denver). She goes on summer roadtrips thru the midwest (95+ in Kansas). Mechanics and rodders are amazed at how easy it starts, no stumbles and the triple venturi primaries deliver decent mileage (~15mpg) while cruising the blue highways. Serious smiles per miles!
Greatest 4-barrel carburetor ever made. A Q-Jet with the bimetal choke coil, and the 1972-style thermostatic / Cowl Induction air cleaner works great. Do a minor tweak or two to the jets and metering rods and it’s hard to beat.
Ethanol gets maligned a lot in the car and carb world, and my experience is that it is unnecessary. Ethanol is alcohol. Like gasoline, it evaporates. The residue that is left behind in your carb is from your fuel system. What I have found is that ethanol is a lot more effective at cleaning shmeg from your fuel system and re-depositing it in your carb when it evaporates. This is generally a short-term condition until you get all of the offending shmeg out of the system. This is done by DRIVING THE CAR sufficient to run a few tanks thru the system. I have had zero issues running ethanol fuel through a multitude of carbureted toys.
I travel a lot and my cars and bikes used to sit for months or even years. I got fed up w carb problems and start using high quality race gas of the correct octane. I had two drums of the stuff. When I left the car / bike was filled and ran w the appropriate fuel leaded or unleaded. I never, repeat NEVER had a problem again. It’s rare to find non-ethanol fuel at the pump and when you do it’s general low octane. Fuel and the poor quality of our fuels is the biggest issue; period!
As far as non ethanol fuel goes New York , New Hampshire and Vermont all have non ethanol at Sunoco stations and it is 91 octane. I just picked up 20 gallons for use in power equipment I repair. I also fill up my motorcycle and hotrod for winter storage.
Florida has numerous gas stations with %100 gasoline – no ethanol – at various octane ratings including 89.
This is not true in all of New York State. NYC and Long Island do not allow real gas to be sold at the pump.
I bought a new chain saw about 15 years ago and the dealer told me to use ethanol shield in gas I have been using it it in my chain saws and weed walkers and my 65 Rambler and I have not had any problems with ethanol gas effecting the carburetors on any of them. You can get it at tsc stores. In my opinion it is better than stabil. It also good for gas that is not used wright away. Just follow directions
Correct. I have a good size collection of 2 and 4 stroke outdoor power equipment and vehicles that only see seasonal use. Many of them require at least 92 octane which I cannot purchase ethanol free. There are two brands of ethanol busting additives that have not failed me yet, Lucas and K100. I highly recommend them to anyone experiencing ethanol related problems.
Nailed it. Quality of fuel. Absolutely essential to keep underhood heat away from fuel that turns to vapor at such a low temp. Pressurized liquid has a much higher boiling point. Thats why a 60 psi FI system doesnt have an issue with todays at the pump fuels. More ethanol(alcohol) lowers the boiling point even more. Isolate your system away from heat and you’re going to have many fewer issues with using old school carburetors…
Fuel up at the gas dock of any marina. No ethanol and they usually have higher octane for the Scarab/Cigarette boats.
NOT SO!!!! I had a small engine that had run for only a couple of hours since new. Forgot to drain it and left ethanol gas in it over winter. The carb was filled with crystals and after cleaning and soaking would still not work. Finally bought a new carb and engine ran like a top.
When I am going to have an engine sit with out running for a long period of time I will run the carburetor dry and have never had a problem with it starting in the spring, good fuel and a dry carburetor and you’ll be good to go
Ditto
If that were the case, then why would every manufacturer of small equipment mandate non-ethanol fuel, from new, to protect the warranty? Ethanol is a problem. It eats rubber and it attracts water that creates rust and scale.
In my area, we cannot buy non-alcohol gas at the pumps, due to EPA mandates. I am very surprised that, with my many older cars, mowers, motorcycles, etc., I have had no trouble, as long as the ethanol gas is used within about a year of buying it. Very surprised. After about a year, though, all bets are off; I have seen what the stuff did to the injectors and gas tank after 2+ years in my father-in-law’s 1990 Voyager V6.
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.
I have an 02 Ranger I bought new with the 4.0 engine. The only time I put ethanol in it is if I have no choice. And then when I can get some real gas I fill it up to dilute it. It has 255k miles and has the original fuel pump. I attribute that to using real gas. Any of my vehicles that are going to be sitting for a couple months will only have real gas in them. 2 of them are capable of 10, 15 or 85% but they have no ethanol in them when they sit.
Alcohol can damage some fuel systems if they are not made of materials that are not damaged by it. Note
Even mixed in small amounts it can be corrosive in older models.
In Racing alcohol you have yo flush the systems after the race with gas to prevent damage.
Most carb rebuild kits and replacement rubber fuel lines today are ethanol resistant. All of the things you would need to change anyway to get a carbureted car going will inherently be replaced with ethanol resistant parts. I have three carbureted cars and a boat with two carbureted motors. I also have several older injected cars which were never designed to run ethanol. I have been running all of them trouble free for years on ethanol fuels. The only ethanol-related issue I have run across was a motorcycle which was stored from the pre-ethanol era and resurrected after ethanol came on the scene. The big issue here was that it was cleaning out the fuel system and, since the owner was not running it often enough, that residue was getting deposited in the carb bowls and gumming up the works. Completely addressable by cleaning the carbs and running enough fuel through the system to allow the ethanol to finish cleaning things up… which the owner did not do. That is the ONLY actual ethanol related problem that I am aware of in all of my travels. I think people ‘hear’ that ethanol is bad the same way they ‘hear’ Quadrajets are bad with no actual personal experience
I love Qjets. I hate ethanol fuel. I have experience with both.
Agreed. 68 Cougar. Original carburetor was good for 115k even w/ ethanol gas BUT I buy no ethanol gas every chance I get and the difference is palpable at 50mph+ at 70mph+ difference is HUGE. 302 V8 original engine. Had not replaced any hoses due to ethanol damage. I use additives about every other tank. Don’t know if they really work but after 20 years I GUESS they help.
Put in rebuilt carb @115k and it’s shot at 134k. So go figure.
Part of the problem in the carb rebuild world is people don’t really know how to do it anymore, and the cores they are using have been rebuilt a hundred times – so I wouldn’t be too quick to blame that on the ethanol
And then there are those of us with British SU carbs. No choke and no accelerator pump. A pull cable physically moves the jet to enrichen mixture for starting. Setting proper running mixture is done by turning a nut below the jet to move it up or down.
My old Porsche has Zenith Carburetors, also without a choke. I guess if you have two 2 barrel carbs feeding four cylinders, you have no problem getting enough gas to start and run.
I quit reading at “non-ethanol fuel.” That does not exist here in New Jersey.
There are a few.
https://www.pure-gas.org/
Thank you for your trouble. This is a handy site.
Half of the NJ stations are airports… I wonder if they actually sell to motorists
I suspect there is one in Alloway NJ that could probably be added to the list
NJ has about 10 such stations. FL has 1,100… another reason to move south.
Not even at your local marina? Ours sells Rec-90 90 octane and ethanol free.
I like old cars ,l would like to know more carburettor cars
I too don’t seem to be experiencing any ill effects from ethanol. It spoils quicker than the gasoline of our collective youth but none of my carbureted cars, motorcycle, small engines, nor Mrs. Tinkerah’s 90’s TBI Tracker show any symptoms. Just don’t let it go stale….I’m a die hard believer in manual chokes too.
I had put a rebuilt 390 in my 67 mustang. Engine builder, a retired ford engineer, said “I don’t install chokes on my old engines. Start it, keep the revs up for about a minute, she’ll run fine!” I pump the pedal 3 or 4 times, it starts right up, hold the revs up around 2k for a minute and it runs perfectly. Been doing this for 17 years now without a choke or a problem!
I 100% agree. Ive owned a lot of old cars that the choke was not hooked up. I just pumped a few times and they always cranked right up. Never seemed to effect my engine/performance one way or another.
Agree, I wire the choke open on my carburetor on both of my old Fords. Couple pumps and they start right up.
You first need compression in the engine.
Once you have the carb removed from the intake, place the palm of your hand over the intake. Crank over the engine. If your hand doesn’t get sucked hard to the intake then you have a bigger problem than the carb.
Use nothing but Top Tier gas to clean the fuel system. My 1984 Mazda RX-7 GS used to buck and stumble occasionally when starting in first gear. I started using Top Tier gas exclusively and the problem went away.
6th thing is the Carburetor bucket!
What is that bucket? I have not heard that term.
I’ll bite… What is the carb bucket?
It’s the thing you chuck your problem carb into when your FI or throttle body system gets delivered. 😉
We have QT gas stations with non-ethanol fuel but it is 90 octane, so it’s a bit of an odd number. Costs more than 93 octane here.
I got a 1970 Pontiac LeMans Sport with a tweaked 455. The real trick to making carbs livable is to get one built to your application by a real pro- not out of a catalog or some one-size-fits-all deal. Factory carbs were specifically tuned to the application, same thing.
Then you need a fuel system that pressurizes the line -in tank electric pump with a return. Mechanical pumps are prone to vapor-lock and just suck on ethanol.
Don’t forget the good plumbing- braided, push-lock.
Costs a lot more than buying a mechanical pump, a Holley and bolting it on connect with cheap with rubber lines (!!!!) but I assure you, when done it will run as well as an EFI car.
Wot no Permatex?
Mixture screws used to vibrate out of adjustment, back when engines moved around a little. When you got everything just right, you’d put *one drop* of tar on the screw to make it not do that. And if your blower fed through a bonnet, you’d use the rest of the can on every single seam in the whole intake tract.
I solved my carburetor problems by giving my son my 57 Thunderbird!