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!
I had one of these for a few weeks (given to me by a used car dealer after a car I bought blew up – bit of a story, and an example of how intimidating my Old Man could be), in 1988. Same red as the first one, with a hooker’s boudoir red velour interior. 5spd with the “racing H” shift pattern, and a beeper INSIDE when you were in reverse so you didn’t do that instead of 1st. That was literally THE only interesting thing about driving that little turd. I traded it to a friend of mine for a pair of skis after I bought my first VW, an ’85 Jetta 2dr. I’m not sure I ever actually opened the hood on the thing, so this fan is news to me.
Certainly an interesting way to help with vapor lock.
Surely phenolic spacer/isolator/thingies were invented by this time. I wonder why the fan instead.
I assume that underhood temps would simply get too high, not just heat soaking through from the manifold. The carb is on the backside of the engine, so likely not much airflow back there without it, and it would be hot air from the radiator anyway. Looks like that the fan is drawing cooler outside air from over on the side somewhere.
While not technically a “carb fan”, many early inline EFI engines with the exhaust and intake manifolds on the same side utilized those fans for the same purpose of managing vapor lock.
The Jeep 4.0L really had to fight fuel boiling when it gained a pair of pre-catalysts (oxidation cats) right below the manifold in 2000 for California emissions and 2001 for Federal emissions.
Some fuel injected vehicles have vapor lock issues. It’s a known issue on Jeep 4.0L engines. Mostly an issue if the injector rail being above the exhaust manifold.
I’ve also experienced vapor lock in the SU carbs of my Austin Healey Sprite, putting an electric fuel pump on it in place if the mechanical pump made vapor lock an issue of the past.
Just wondering what kind of car you’re driving that feeds fuel through the intake manifold to the carb? Just curious, ’cause I’ve never seen one like that.
Mostly, vapor-lock occurs in the fuel line before the carb–sometimes before the block-mounted fuel pump (where the fuel is under suction). Our cure for it in the old days was a wet rag or rags wrapped around the fuel line. Re-wet when the engine stalls a half-hour later. Repeat.
Yup that vapor before the pump causes the pump to loose prime and stop pumping.
yeah, i was sloppy there. I fixed it. Thank you!
Great story by PJ O’Rourke about his car stalling, possibly due to vapor lock, in front of a bar: Roadmaster Reruns: Sgt. Dynaflo’s Last Patrol
My ’78 Corolla often gets vapor locked. I’m going to put a fan in there. Thanks for the idea, Torch!
A fan pointing at the carb won’t fix vapor lock, it is there to prevent percolation.
“One of these big issues was vapor lock, “
That was my guess why they were needed right off the bat.
Ditto!
“I Had No Idea Carburetor Fans Were A Thing”
Really? Because I’ve definitely found some in the comments here.
Bunch of total perverts.
I hate my carb and can’t wait to yeet it into a volcano.
I refuse to throw out a 40 year-old stethoscope that I’ve got in a box because I expect I may get to balance some Webers or Zeniths at almost any time. Any time at all now.
I had a charming quip here but unfortunately it was intended to be a response to another comment , so this lame ass comment will have to do.
The ’70s and ’80s were a really interesting time if you worked on whatever rolled into the shop.
It seemed to be worse in the 70’s as engineers tried to run cars hotter and leaner to reduce emissions and get better MPG.
Now a days, it seems to be fuel related. Even Non-Ethanol Fuel seems to boil much faster in my Scout. I may be incorrect, but it sure seems like this though.
Make sure you use the proper heat dam style gasket that has the section that extends underneath the fuel bowl to divert the heat radiating from the intake manifold.
I was thinking some heat shieling on the fuel line since it passes between the upper rad iron 90 degree turn out. But yeah, maybe the actual bowl boiling is the issue. I will see if the gasket is correct like that.
Yeah I haven’t had an issue with any of my SV equipped Internationals when equipped with the heat shield gasket, not that a heat sleeve wouldn’t hurt because of the way that line runs from the pump to the carb.
The 1980s/90s (just) Renault 5 GT Turbo was fitted with an ‘anti-percolation fan’ as it was notorious for failing to proceed on a hot start (and it did get hot under its little bonnet/hood when driven as God intended).
Even back then Renault were pretty much in the minority for sticking with a carb when most other manufacturers of hot hatches were pointing at the little ‘i’ on the tailgate and nodding knowingly.
That said, when the means of combining fuel and air was playing ball the things went like a stabbed rat so Renault were forgiven..
I think the thing that really eliminated vapor lock was the design of constant flow fuel systems where the fuel pump would pump mech more fuel than was required, and a second fuel line would return the excess to the fuel tank. That and putting the fuel pump in the tank so the fuel line was pressurized rather than a fuel pump in the engine compartment sucking the fuel through a lower pressure line.
I think that happened at about the same time as the widespread adoption of EFI. Older fuel injection systems with mechanical pumps suffered from vapor lock. The Bosch pumps were a really fun if you needed to purge the system.
this might be a lot of it. I know a common fix(bandaid) seems to be installing an electric inline fuel pump back by the tank and one of those return line fuel filters with a return line plumbed definitely seems to help.
https://quadrajetparts.com/fuel-filter-universal-metal-wreturn-line-p-2485.html?gQT=1
Yup the return style systems were to prevent vapor lock and a number of carb vehicles with mechanical pumps used them before fuel injection became mainstream.
On the Fiat X1/9, the carb fan was ducted to one of the black plastic air scoops on the side of the car. This way, the fan drew in ambient temperature air from outside the engine compartment and blew that air onto the carburetor. Don’t forget that the X1/9 was mid-engined so the engine compartment was kinda small. I believe that the system had some sort of temperature-sensitive switch (with a timer?) so that the fan could run after shutdown. By the time I bought my 1976 X1/9 (in 1990) I think that the carb fan system was missing.
So here’s a few engineering fun facts for you:
Worth also mentioning that not all manufacturers adopted fuel injection at the same time. The last carbureted Ford for North America was the 1991 Crown Vic 351 — everything else had been become fuel injected, even the ancient stove bolt four-cylinder found in the Topaz / Tempo. (The Datsun shown here is a MY 1982).
Excellent comment. Thank you
Modern vehicles are almost all exclusively returnless fuel injection. Eliminates a pipe and reduces fuel heating in the tank (and thus emissions). They simply have raised the fuel rail pressure high enough to prevent vapor locking (60+ PSI).
Diesels have a fuel cooler because the high pressure common rail injection pumps put a tremendous amount of energy into the fuel that turns directly into heat (think like how hydraulics get hot), and the fuel temperature (and thus viscosity) is important to maintain to ensure accurate injection.
Most modern EFI systems are returnless, to prevent heating of the fuel in the tank.
Some Mercedes use air conditioned fuel lines to prevent vapor lock.
I had a ’67 VW Bug back in the late 70s. I’d fitted a Holley Bug Spray to it and a big quiet pack exhaust system to it to boost its paltry performance.
The Bug Spray had endless issues with vapor locking and I bet a fan in there would have helped things on hot Georgia days.
Vapor lock was also a major plot point in Stephen King’s novel Cujo, if I recall, in a Ford Pinto.
IIRC that Pinto didn’t start because the carb was either dirty or not jetted properly.
Granted its been what, 40ish years since I read that book.
I got vapor lock in a fuel injected Volvo 740, but that was driving up Pikes Peak. I had a pretty good idea of what was wrong but my AAA card carrying wife insisted on using it even though the problem would’ve gone away by itself. Tow truck guy arrived looked at the New York plates on the Volvo and first words out of his mouth were “Did you fill it up in Kansas?”
In college I had VW Dasher withe the opposite problem. In New York freezing rain or any cold but humid weather, the carburetor would fill with ice. My pilot friends found it amusing.
I think there was probably some duct work that was missing.
Anyway, a reminder of our friends Venturi and Lord Kelvin.
My 1952 John Deere tractor has a massive (5.3 L) 2 cylinder engine. The carb on it gets frosty even in the summer due to the huge amounts of fuel vaporizing in it. Having the carb over the exhaust manifold would have been a huge help to it. The dual fuel versions were more finicky than the gasoline engines because they needed even more heat to work well.
The answer to “Name a single seater with truly impressive wheel stagger, carburetion like an airplane, a gated shifter like a Ferrari, cylinders bigger than a Rolls Royce Merlin, and painted like a Lotus.”
Hahaha. You know your old tractors. I do love that 6 speed gated shifter, it is very sporty.
And easy to use torque vectoring!
The dual brake pedals were soooo much fun.
Our 720 was pretty nice for row crops. Pretty miserable in the orchards. Oh and of course after the muffler got knocked off by a tree a few times we stopped putting it back, and it made a great sound.
And that’s why they were called “Johnny Popers”.
The first tractor I learned to drive was a 730 diesel! They are such cool tractors.
The early SAAB 93 (no dash) may have had the same iceing problem. There was a piece of removable air duct (held in place with latches) that connected the carb to an air intake mounted on the exhaust manifold. IIRC you were supposed to hook it up for winter. (You could also close the window shade that blocked air coming in the grille, but that was done from inside the cab.)
… would become become vaporized in the [fuel line or carburetor body]
intake manifoldbefore it got to the carb …Some intake manifolds are actually designed to vaporize any liquid fuel that makes it in.
Very early automobiles from when carburetors were even more so a black art worked on the theory that the gasoline needed to be vaporized. At least one manufacturer tried to a system where instead of a carburetor, intake air would bubble up through the gas tank, and then to the engine. Needless to say, an engine backfire would be a catastrophic event.
Smokey Yunick did some cool things with vaporizing gas, I think on a Fiero? If I remember, mixture was heated by the exhaust. A turbo was present not to improve performance but to keep the greatly expanded gases headed the correct direction.
I recall an ad in the back of some car magazine for a piezoelectric fuel atomizer that was supposed to supplement insufficient carburation. Might have been the Fuel Shark of its day.
No carb fan info but my Volvo V70R had an ECU fan that would continue running after the engine shut off.
Some MINIs (not sure which ones exactly) have a fan underneath that blows up at the power steering pump. The guys at my local shop told me they occasionally suck up a plastic bag, stop, and the pump overheats.
My e91 and e88 BMWs have the ECU fans too, but AFAIK they don’t run after shutdown. Some modern cars put the ECU inside the intake manifold for cooling.
You aren’t kidding: https://www.pelicanparts.com/techarticles/MINI/48-SUSPEN-Power_Steering_Fan_Replacement/48-SUSPEN-Power_Steering_Fan_Replacement.htm
I’d take a bit of minor wrestling at low speed with a former roommate’s (similarly-sized) ’94 Civic’s manual steering over dealing with that, for sure, especially given the different ratio/additional drag of a power rack when things suddenly go wrong.
Related to the 310, the hatchback had remote control pop out rear windows, operated by levers similar to VW Beetle heater controls.
That carried over into early Sentra hatchback coupes.
I had my own vapor lock experiences myself when my dad bought me a 1986(technically a 1985.5) Ford Escort Pony 3 door hatchback equipped with a Holley 2 barrel carburetor that loved to vapor lock after the car did high speed driving and/or driving in high temperature environments. The joys of driving in Northern Illinois in the middle of June or July!
I never had vapor lock issues with my ‘86 Pony (four speeds!) but I did have a “winter” thermostat (thanks dad, upstate NY winters can be hard…) that didn’t like running 80 mph in the wide open west on a road trip…I learned not not fear the flowing red eye of the “engine” light…I also pulled off the grill to let more air in.
I had a 4-speed as well. Interestingly enough,mine was built in Canada.(Ford’s plant in Oakville,Ontario was very busy cranking out Escorts and Tempos). If Dad had gotten an 1987 Pony it would’ve had CFI(Central Fuel Injection a.k.a. throttle body injection) which was more reliable and cancelled out the vapor lock issues.lol
The Escort I had eventually met it’s end in Addison,Illinois near I-355 and Army Trail Road when aforementioned Holley carburetor caught fire,resulting in the car’s front end being BBQ’d!
Ouch.
Mine got a five-speed swap out of a wrecked ‘87 Wagon and now rests, moldering into the ground at my parents house. It’s visible on satellite images!
Yup. By the time the Addison Fire Department showed up the fire had warped the hood-and hoods on Ford Escorts(and its twin-the Mercury Lynx) weren’t exactly known for being lightweight!
Dude. That’s a fanocharger.
Yes my Datsun has a blower from the factory.
Sure Jan.
Electric blowers have since evolved into weird science
Carbs are good but emissions regs made them weirder and weirder until they disappeared. Fans and heaters fixed the environment in two directions.
Cheaper magic engine circuit boards killed ’em, but I’m still a fan of carburetors.
Just found a tackle box of Keihin stuff today. Every brand needed one and some multiple variations. Trading jets at the track was a sign of friendship.
Carbs are good but emissions regs made them weirder and weirder.
I present the California FJ40…
Not shown, switches on the speedometer to change the mix at certain speeds.
Yes, it had a fan, but I ditched the OEM for a Holly carb, never finished it enough to get it on the road and to emission testing.
holy moly. That is a nightmare of vacuum lines.
That’s California emissions vehicles for ya!lol
I’ve spent the last – checks calender – several decades here in California and in that time I’ve had to get a lot of cars through CA smog. I’ve only failed to pass on the first time twice, once the fix was a simple idle mixture adjustment and the second was replacing a cracked plastic intake flexpipe. Cheap, easy fixes that made the cars run better.
Aside from the hassle and expense of getting a car smogged I don’t get the hate – would you prefer to live in a carburetted world WITHOUT emission controls? Because I have and I can assure you, you do NOT want that! Especially since there are about 2x as many people in the world today as then with a higher percentage of drivers. Only being downwind of a major wildfire even comes close to the experience.
Electronic controlled carbs. Because spfi was too simple and easy *in the same car*
Yes Subaru sold that weirdness at the same time they had turbo engines and mpfi on the high end and spfi on simpler engines. Then the wierd carb crap.
Carbs can have good power/drivability, good efficiency, or low emissions – pick any two. The war crimes done to them to try to try to get all three never really worked, and ultimately fuel injection became simpler and cheaper once electronics got cheap.
The properly rebuilt and upgraded with delrin throttle spindle bushings SUs in my Spitfire are delightful, but that car pollutes the environment more sitting in the garage over the winter than my SULEV BMW does belting down the highway at 70mph. The evaporative emissions alone are horrifying.
Seeing that Datsun 310 brought back memories. My father had one-blue with the black vinyl top. Unfortunately, its life was very brief as it was totaled barely 3 weeks after my dad bought it. The Datsun was rear ended while parked when Dad went to the local convenience store to get his usual morning newspaper for work.
Ironically,that saved his life.
When he came out, the car was half of its original length! Datsuns and Nissans of that era were typically with Hitachi carburetors, which were notorious for being troublesome – especially with vapor lock issues.
Since the 310 was out of production at the time (the Datsun nameplate was being phased out and replaced by Nissan here in the U.S. as a whole).
Dad took the insurance money and bought a new black 1984 Nissan Pulsar NX coupe-which another twist of irony, was equipped with the aforementioned Hitachi carburetor , which actually left Dad and I sitting on a side street in my hometown once because it vapor locked!!lol
Good times!!