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Stop being afraid of your carburetor

To many automotive enthusiasts, the carburetor exists on a level somewhere between mystery and magic—but I’m here to tell you that it’s not so scary to rebuild one. If you like working puzzles or building model kits, you already have the skills you need.


This is a companion discussion topic for the original entry at https://www.hagerty.com/articles-videos/articles/2019/02/15/stop-fearing-your-carburetor

Rebuilding carbs is a zen activity for me. I enjoy it, almost too much.

Tuning one is quite rewarding as well.

Unfortunately, there is a scarcity of mechanics who are left that know what they’re doing around carburetors. My 1972 De Tomaso Pantera was always such a pain in the neck to start as I would nearly always have to pull the air cleaner off, dump gas into the carb, run back into the car, hope that enough fuel was still available to start it, turn it over, run back out and put the air cleaner back on, and hope that everything stayed running. I’d had the carb rebuilt, replaced with a new one, but the problem never was cured. It was ultimately what led me to fuel injection replacement and a restoration/modification of my car. Four years later, it now starts first time I turn the key and rumbles to life. I won’t miss my carb, good riddance!

@tberg - That sounds like a heat issue. Boiling the fuel out of the carb when shut off, which causes a lot of cranking to fill the bowls for startup-especially with a standard mechanical fuel pump. Also explains why a carb switch didn’t cure the problem.

The one touch start of fuel injection is quite nice though!

A couple of things to watch our for when rebuilding any carburetor. One is a worn throttle shaft. The hole in the base casting can become worn over time, allowing air to be sucked in past the shaft. This will lean out the fuel mixture, possible causing lean misfire, hesitation or stumbling problems. If the throttle shaft hole is worn, it can be fixed by removing the throttle shaft, drilling out the hole to oversize and installing a steel or brass sleeve to restore normal clearances.

Another problem to watch out for is a bad float inside the fuel bowl. If the float is brass, shake it to see if there is any liquid inside. A small hairline crack in the seam can allow fuel to seep into the float, causing it to sink and flood the engine with too much fuel. Many carburetors also have plastic floats instead of brass. Some plastics soak up fuel over time like a sponge, making them too heavy. This causes the float to ride too low in the fuel bowl and flood the engine with too much fuel. The fix for a bad float or a heavy float is to replace it with a new one (f you can find a replacement).

I am frustrated with the lack of replacement jet sizes for modern fuel (ethanol). Gas today isn’t the same as it was when my carb was designed over 50 years ago. Yet, when you buy a rebuild kit the jets are all per the 50 year old design. Modern fuel doesn’t burn the same. When will someone start selling a fix for this so the carb works as it was designed too?

Funny, I am also the owner of a 72 pantera. Had the original Cleveland with a 650 CFM holly for many years. But always had starting issues after I had driven it for awhile. Due to circumstance, I changed to a 351 Windsor and still had some issues with the starting after the engine got hot. Decided to install a Holly fuel injection system. Now it never hesitates to start and run great. I can be in the mountains at 8000 feet or down closer to 2000 feet, she just starts and runs

A few things you forgot to mention here:

  1. kitchen table
  2. taking apart the carb clockwise, so as to re-assemble counter clockwise. Indeed, if you follow this simple procedure, you almost don’t need a manual.
  3. preferred carb cleaner? I’ve heard tell of some people letting their carb bodies soak in gasoline instead of carb cleaner.
  4. Single barrel vs. double barrel carbs
  5. (perhaps Hagerty Kyle can do this-a little blurb about carb synchronization, since some cars have more than one carb?)

Kyle

I’ve rebuilt so many Autolite 2100/4100 carbs over the years, I could probably do it in my sleep!

Another trick. Get a gallon can of Berryman’s Chem-Dip. Last time, I got it at Walmart. Just dunk the parts and in 10-20 minutes, the crud is easily removed.

Also, I usually switch the choke thermostat out for an electric one. The mid 70’s Autolite 2100 electric choke will bolt right on. Sometimes there’s interference inside, but if that happens, I use 2 of the ring-style gaskets. Then I hook it up by running a wire to the stator lug on the alternator (if you look at a mid-70s Ford wiring diagram, that’s where they connected it). Put in a fuse for added safety. Most likely, the heat tubes will have already rusted off the exhaust manifold. I just cut the hot side off an inch or two from the choke, and run a hose up to the fresh air connection on the air horn.

The only car I haven’t converted is my 64 Galaxie with a generator. I haven’t tried this yet, but I read a suggestion online to swap the oil pressure sender out for one from a 70’s Chevy Vega. It’s supposed to have an extra lug you can use to power the choke from any 12 volt connection, and only supply power to the choke when the engine is running. I’d put a fuse on that set-up, and maybe try a Holley electric choke thermostat that’s meant to run on 12 volts.

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dennis1,
I also installed the Holly fuel injection, and find it hard to believe that all I have to do now to start it, is to turn the key. I am still having some vapor lock problems due to engine heat which we are addressing this week. I was just never driving the car because of the difficulty in getting her started. I am looking forward to getting the big cat back this weekend. Do you have a picture of yours?

ponyconvertible, if you are using a Autolite carburetor, you can purchase many different (including larger) jets for your carburetor. Holley jets are the same as those used in Autolite carburetors. They are available in duplicate pairs, and also in sets (ie, 10 different pairs). You may want to buy one of the sets so you can tune in the right AFR.

69 F100 ranger
This is quite a co incidence, I just completed my 1st rebuild on 360 to this exact carb! You are correct, I’m not a mechanic but am a tradesman so it wasn’t that difficult of a job, thanks to internet and you tube! I have installed it but still have to fire it up and fine tune.
I also am having problems with hot starts, Anymore than 5 min sitting when hot I have to floor it and let’r crank until it finally starts (never left me stranded though)
Im trying to do all the simple thing 1st and so far I have insulated the steel fuel line changed the coil and rebuilt the carb. The truck is 100% original so I’m trying to avoid electric fuel pump.

Send me a message to discuss Pantera

Dennis Franks

My F100 had an old crusty 2150 motorcraft carb on it when I bought it, almost the same as the 2100. Rebuilt it just to get it moving around and check the truck over. Worn out throttle shaft, seized accelerator pump, leaking power valve, corroded screws and an awful fuel boiling problem. Found a brand new 2150 (not a reman) was only 125$ on Ebay and works great till this day.

Hi Dennis,
I sent you an email reply.
Thanks,
Ted.

There was a time…everyone can agree that there is no better sound like that of all 4 barrels wide open and the grown of the engine resinating from under neath the hood…kinda miss that with fuel injected , throttle plated engines of today…as tech moved us on and we didn’t need 4 barrel, two barrels or even cabs at all…the art of carb rebuilds slipped away… swapping out a new one or re-manned one took over…then we somehow went back to carbureted engines because you don’t need to smog checks anything that was built before OBD!!! How life tosses you a chocolate covered cookie every now and then…

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