The Wind Or The Carb

[CatMan1]

We took our '28 Sport Coupe to the Model A Day in the Amanas this weekend. It's 82 miles one way. It did really good going there. I did notice what I thought was wind gusts blowing us around or maybe just pushing the wind since the car isn't very aerodynamic. Does anyone else feel the wind when driving these? However when we went to leave I had to really crank on it to get it to start. Like it wasn't getting any gas. When we stopped for fuel it wouldn't stay idling unless I really revved it up. We almost couldn't get going, but I kept up-shifting and got it into high and we made it home. I'm suspecting the carb needs cleaned or rebuilt. It has the pencil screen in the tank and the one at the sediment bulb. Maybe what I thought was the wind in the morning was the carb causing it to surge? It also tends to backfire through the exhaust. Thoughts? (We had planned to clean the points, but ran out of time.)

[Will N]

What was the temperature on your way home? Was it hot? Sounds like you could have been experiencing vapor lock.

[Rob Doe]

Wind is definitely a factor, especially a strong cross wind that is gusting. Backfire through the exhaust is usually a rich mixture. Sometimes a novice will mistake an exhaust leak for a backfire.


A backfire through the exhaust is sometimes referred to as an after-fire. A backfire through the carburetor is referred to as a backfire to delineate between the two. The backfire through the carb is a lean condition.

[Rob Doe]

Cleaning and setting the point gap would be the first place to start.

[JayJay]

I definitely feel wind, especially at highway speed when running close to max what the car will do. Of course, a headwind going out can turn into a tailwind coming home…

I’d also start with points before tearing into the carburetor. I’ve had similar symptoms as yours that were resolved by regapping.

[Fullraceflathead]

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If the points don't look very good at all you might try changing the condenser.

[CatMan1]

Originally Posted by Will N

What was the temperature on your way home? Was it hot? Sounds like you could have been experiencing vapor lock.

It was a warm day....around 80. The symptoms got worse after I filled up. The station only had Ethanol as an option so I wonder if that was a bad idea.....

[CatMan1]

Originally Posted by Rob Doe

Wind is definitely a factor, especially a strong cross wind that is gusting. Backfire through the exhaust is usually a rich mixture. Sometimes a novice will mistake an exhaust leak for a backfire.


A backfire through the exhaust is sometimes referred to as an after-fire. A backfire through the carburetor is referred to as a backfire to delineate between the two. The backfire through the carb is a lean condition.

It's definitely after-fire, then.

[CatMan1]

I'll for sure be checking the points. I've had the car for three years and I don't recall ever having replaced them.

[JayJay]

Originally Posted by CatMan1

I'll for sure be checking the points. I've had the car for three years and I don't recall ever having replaced them.

Be careful on replacing. Some of the aftermarket points had the arm the wrong length and they don't line up with the point block properly. The vendors sell a special point block that resolves this issue for those points.

See the note attached to Snyder's part number A-12160-X. Best bet is to order new points and block at the same time even if you don't think you need to replace the block.

[ModelA29]

Originally Posted by Rob Doe

Cleaning and setting the point gap would be the first place to start.

A carb guru told me when troubleshooting he finds a lot of owners "fuel" problems are electrical in nature. If the spark isn't right it's not going to run right......

[Big hammer]

Check the points first, clean and set the gap before changing parts, you’ll save time and money !

[Will N]

Originally Posted by CatMan1

It was a warm day....around 80. The symptoms got worse after I filled up. The station only had Ethanol as an option so I wonder if that was a bad idea.....

When you stop the engine (or even come to a prolonged stop, like at a red light), the lack of airflow through the engine bay allows the heat to soak the carb and fuel lines, making the symptoms of vapor lock even worse. Gotta get moving to get the airflow to cool the carb.

[gdmn852]

Hello, if the problem started after the ethanol, I might suspect that being the cause, I try to avoid ethanol if possible, some time have no choice. As far as feeling the wind , yes it’s noticeable, cars of this era are as aerodynamic as a brick.

[David in San Antonio]

Re: aerodynamics - Buckminster Fuller claimed that conventional sedans (shaped like the Model A) had so much aerodynamic drag they were more efficient running backwards rather than forwards. He then went off the deep end, designing the Dymaxion automobile with a teardrop shaped body on a tricycle chassis with two front driving wheels and one rear wheel which steered like a rudder. Oh, and the engine was in the rear with a drive shaft to power the front, non-steering axle. He built three prototypes. The aerodynamics made them very fast. The rear-only steering allowed them to turn 360 degrees in their own length, but was treacherous to drive. You can read a modern test drive in the Car & Driver archives. Maybe it’s on the web.

[Bob Bidonde]

I once drove my Model A Coupe from Baltimore to New York in a hurricane. The Coupe ran fine in the high winds and driving rain. Moreover two semi trucks kept me between them all the up I-95 and the water spray the front truck kicked-up had no effect on the motor, but the spray made vision out of the windshield difficult. I had a CB radio back then and the truckers made surrounding traffic aware my Coupe was between them. I love those caring truckers!