I think I’ve mentioned before how I’m continually astounded at how there’s always something new to learn in this vast universe of automobiles. I’m a painful car geek, one that makes people fling their drinks into plants at parties just to get the hell away from me before I pin them into a corner and start talking about turn signals, and even I find things I had no idea existed all the time. Like just recently when The Bishop sent me a link to this Facebook Marketplace ad for a 1982 Datsun 310GX, and told me to look at the picture of the engine bay.
I’ve mostly forgotten about these old Datsuns, but I remember liking them in a pretty mild way back in the day. They were appealing in a sort of quiet way, similar to other transverse FWD economy cars of the era, but with somewhat different proportions, and I don’t remember these being quite as common as VW Rabbits or Dodge Omnis or Toyota Corollas.
Also, they had some cool coupé variants with great bubble-glass rear windows:
But we’re not here to talk about the exterior design, the weirdness is under the hood! So look at this:
Do you see it? It’s weird. Here, let me show you:
There it is; that fan. A little fan in the engine bay, not anywhere near the radiator or any part of the HVAC system, but still clearly a factory-installed part.
And it’s not just on this car! You can find videos and pictures of other people “discovering” these fans (you know, Columbus-type “discovery” of something that was already there) and also wondering what the hell they were for:
They are quite a little puzzle! They look like little desk fans with their wire anti-finger-chop cages. Here’s another video of some fan-discoverers:
So what are these fans? They appear to be pointing at the carburetor, nestled there under the big air cleaner drum. But why?
These carb-cooling fans aren’t unique to Datsun 310s, but they’re close. Doing a bit of digging with the help of The Bishop, I’ve only been able to find two other cars that have carb fans: the Fiat X1/9 and the 40 and 60 series Toyota Land Cruisers.
So, again, what was going on here? Why did these cars feel the need to blow air on their carbs, unlike pretty much every other car ever? The answer is, of course, the only true answer to any confounding question: sometimes, things just kind of suck.
In fact, our old pal Murilee Martin made mention of this very fan and its purpose while exploring a junkyard a few years back, and his assessment is the correct one. These fans exist because carbs, fundamentally, kind of suck.
I mean, they’re amazing machines, strangely complex little analog computers that deal in fluids and air and vapors, creating miasmas and admixtures like little clockwork alchemists, but they were also vulnerable to all kinds of trouble from such vast and untamable factors like weather and ambient heat and atmospheric conditions.
One of these big issues was vapor lock, where the fuel, largely due to excess heat, would become vaporized before it got to the carb, creating all kinds of fuel delivery problems and making your car stall, frustratingly. This was especially common for cars with inline engines that positioned the carb or carbs right above the piping-hot exhaust manifold.
My old Volvo 1800S was like that, and would often drip fuel from its twin SU carbs right onto the exhaust manifold, where it would smoke and sizzle in a nicely terrifying manner. And, yes, sometimes I would get vapor lock.
So these little fans were an attempt to mitigate the national scourge of vapor lock, by attempting to cool that carb down so the fuel wouldn’t be trying to come in as some ghostly cloud. If you don’t believe me about how much vapor lock once held America in its cruel, wispy grasp, maybe you’ll believe an animated version of former New York Jets quarterback Joe Namath:
See? Now who’s laughing? Not Broadway Joe, that’s for damn sure. He gets it.
As did, it seems, Fiat, Toyota, and Datsun, at least on some select models.
Vapor lock really hasn’t been a major issue for decades, as the problem was pretty well eliminated with the widespread adoption of fuel injection. Still, it’s interesting to see what sorts of somewhat desperate-seeming measures were used to combat the inherent sloppiness of old carbureted fuel systems, and again, I’m sort of amazed this is the first time I’ve encountered this particularly quaint solution.
Can any of you impressive car geeks think of another car that used carb fans? I wouldn’t be surprised if there are more!
This is the kind of OnlyFans content that I’m looking for.
It probably needed it. My dad (and later me) had a 1983 Sentra wagon with a 1600 4-cylinder that looked just like the one pictured. It would vapor lock on hot days after shutting the engine off so consistently that he kept a little squirt bottle of gas under the hood to get it restarted. At some point, we figured out that Nissan had a TSB out for it and a revised three-port fuel pump, which mostly fixed the problem.
To be clear, using the word “discover” to describe what Christopher Columbus did, or what the FAN fanboys did, is correct. It does not imply, as suggested, that America didn’t exist before Columbus discovered it. It’s perfectly ok to say “I lost my glasses, and discovered them sitting on the Jaguar’s roof,” or “One day, Autopian will discover journalism.”
Or “one day, Pc Mast will learn how to get their head unstuck from their ass”
When does hell freeze over?
Cars like my 81 reliant 2.6 HEMI with all of its blistering horsepower and my 89 accord which is actually fuel injected it would run the radiator fan after shutoff to help mitigate vapor lock. In true k car fashion if you leave the sensor that triggers it plugged in and the timer relay messes up the alternator catches on fire (there was a tsb)
My first car was prone to vapor lock in warm weather. I’m so glad I don’t have to deal with that anymore.
Well, I learn something new about cars all the time too. 🙂 I did NOT know that vapor lock didn’t affect fuel-injected cars. I’ve had a few cars with carburetors but never really had to mess with them, so I don’t really have much hands-on experience with them, and as far as I can recall, I’ve never experienced vapor lock (AFAIK).
I must admit I didn’t really even know what vapor lock is, despite having heard the term now and then for almost 50 years. I assumed that it had something to do with fuel vapors getting in the way and not allowing ignition/combustion to take place as intended. As recently as just last week, when I followed a neighbor in his early 90s Nissan pickup to his mechanic because it was hard to start sometimes, I even vaguely posited that ‘vapor lock’ might be the problem, even though I really didn’t have any firm understanding (his truck is fuel injected). My tone of voice was probably that of a game show contestant guessing an answer, and the mechanic was too polite (or didn’t care) to correct me.
It turned out to need a new starter, and we’re picking it up today. That old Nissan is primitive (loud, bumpy, etc…) but it definitely has that ‘will run forever’ vibe.
Also, that 310 coupe is adorable, and even a little bit sexy. Wish Nissan still made cars like that now… visually, the Versa, Sentra, Rogue, etc… are all a bit of a snoozefest in terms of exterior styling.
Old Jaguar XJ’s had something similar for the 12v battery. I guess that there wasn’t a lot of room/airflow so this was a concern? (probably more of an issue for V12 models)
https://www.worthpoint.com/worthopedia/jaguar-xj6-12-series-3-battery-box-246961015
I was thinking this was going to be more like those dumbass ebay “electric turbo” fan things you could buy in the early 2000s.
I clicked thinking fans referred to those knuckle dragging carb aficionados, so I’m even more wrong.
The ’86 Voyager I had vapor locked at the drop of a hat. Could have used one of those.
I have a 718 Boxster, it has engine compartment fans being mid- engined it has no air circulation in there. Porsche engineers even stated no motors larger than 4 liter because of “thermal” concerns would be placed in the 718 series.
The only vapor lock I ever experienced was in about 1971 when dad’s 1967 VW beetle vapor locked on a hot day in Maryland.
I do remember reading a tip, I think in an old Motor Manual, to put half a grapefruit or orange on your mechanical fuel pump to prevent vapor lock on a hot day. I suppose this would be a go-to solution in Florida back then.
That sounds both plausible and someone telling you the old blinker fluid joke all at once.
The article in the manual had photos / illustrations of the old mechanical fuel pump on the side of an engine, and a grapefruit squeezed over the top of it. I don’t remember if there was any way to keep the grapefruit in place, or if you had to stop every time you got vapor lock and apply the grapefruit to cool it down. But it was real. It was published at a time when a “content provider” had to have demonstrable proof of the fix. It was in print, you see.
I wonder if room temp grapefruit is fine or they need to come from a cooler first
I read “Carburetor Fans” in the headline and I thought surely this is another psychedelic Jason fantasy. Nobody likes carburetors!
I love them. You can fix generally anything with a flathead screwdriver and a pair of needle nose pliers and they are not electronic. What’s not to like.
Facebook Marketplace; Where a GX becomes a ZX. The place to get a Datsun Z.
I have to admit, when I read the headline, I thought you meant ‘fans’ as in ‘fanatic’.
You know, like how you are a ‘fan’ of taillights.
It’s there to direct the Psychotic Reactions and blow away the Carburetor Dung!
It wasn’t just cars. I recall reading that some small aircraft engines were prone to it on hot days and made the plane hard to start after sitting and heat-soaking the fuel line for an hour or so. Particularly ones running autogas and parked at higher altitudes.
This is an old article but discusses the issue:
Aircraft Engines Auto Gas
Once started, there’s a big fan out front and as far as I know it wasn’t a problem once started or in mid-flight. Which is good.
It has nothing to do with vapor lock. Vapor lock occurs in the fuel line, before the carburetor. It is to prevent percolation which is when the fuel boils inside the fuel bowl. That causes the level of the fuel in the bowl to rise, pushing it up and out the venturi. That causes hard starting due to all the excess fuel in the intake. I don’t know about the other brands but on the Datsun F-10 and the 310 the fan runs after the engine has been shut down and when, not if, the sensing system fails you come back to a dead battery.
That makes sense. Now that you mention it. I remember turning a tractor engine off for some reason, and it flooding when I tried to restart it.
Makes sense. My two old cars are sometimes difficult to start after being driven and its likely from what you mentioned. The fuel gets boiled out of the carb. Its especially noticeable with my 49 Plymouth that has the carb sitting on top of the exhaust manifold.
My old 1970 F250 with a 390 would always start hard on hot days. One time, I pulled the carb horn off to check the float level while it was hot, and the fuel in the bowl was vigorously boiling away! I never even knew percolation was a thing before then. A phenolic spacer helped keep the blazing hot cast iron lump from boiling the carb on all but the hottest days.
I swear until I started reading the article that the headline made me think that you had no idea that there were car guys that were fans of carburetion!
I’d never heard of carb fans.
Yeah, when I first read the headline, I thought Jason had just discovered centrifugal superchargers.
“My old Volvo 1800S was like that, and would often drip fuel from its twin SU carbs right onto the exhaust manifold, where it would smoke and sizzle in a nicely terrifying manner.”
As did my Triumph. Good times!