Hagerty.com

5 off-beat carburetors you’ve got to check out

A single four-barrel carburetor on a V-8 or a row of sidedrafts on an inline six-cylinder are conventional today, but it took over a century of hits and misses playing around with carburetor technology before these setups became the accepted norm.


This is a companion discussion topic for the original entry at https://www.hagerty.com/articles-videos/articles/2019/09/11/off-beat-carburetors-to-check-out

“Decades of heat cycling and subsequent core damage gave the Thermoquad an undeserved bad reputation.”

I am confused. Also, I suspect that the 1957 Thunderbird had a 312 ci V8 engine. Even Chrysler couldn’t have extracted 285 hp from 212 ci in 1957.

@cj1 - Thanks for pointing out that 212 mis-print. We’ve got it fixed.

Another good one for the list is the Predator. Concept on those was pretty wild.

On Thermoquad: “Thermoplastic. The center section of the Thermoquad was molded from fiber-reinforced phenolic resins for reduced weight and favorable fuel cooling.”
Fibre reinforced phenolic is ThermoSET, not thermoplastic. Thermosets are shaped and then cured by means of a cross-linking agent, e.g. polyester (fibreglass boats etc), or under heat and pressure like rubber. Thermoplastic has to be melted and then shaped in a mould ; polystyrene, ABS, pvc, stuff like that.

Nothing like trying to synchronize a pair of SU carbs. The bigger (HD-8) the better. I hope to soon be performing that chore on my 1966 Austin Healey that I am converting to triple HD-8 SUs. I know it will be FUN!!

Hard to believe nary a mention of the most venerable SU carb from Skinners Union. A model of form follows function design. Stromberg too had its following.

I still have a first-generation Kendig carburetor that we ran on a competition ski boat. And I still can’t remember why we took it off.

The 1926 Ford “T” also had a vaporizer carb. It allowed the engine to burn almost anything for fuel, including kerosene. At 4.25 to 1 it doesn’t even knock that bad on kerosene. I does however make the T even slower.

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At the “Chryslers at Carlisle” show a few years ago, a swap meet vendor had a 10’ x 10’ tarp on the ground covered with thermoquads. The sign read “$5 each, your choice”.
There were no takers.

The 2V Variable Venturi Carb was used by Ford in the Late 70’s. In theory it was a great idea. But in the real world it was very troublesome. Not sure if it was used nationally but in California, had one on our 78 302 V8 Mustang II (Mice-Twice). Replaced it with a conventional Holley 2V, it made a world of difference. Later an early 2V Holley ProJection, but that’s a story for another time.

I know it’s injection, but since it was marketed to replace a conventional carb we have to give mention to “Ron’s Flying Toilet” if for no more reason than the pragmatic engineering and it’s ease of replacing a good ol carb.
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If it’s too off topic go ahead and delete, but the name and it’s success deserves at least a small slice of raisin pie, no?

Yeah, I’m surprised the Predator isn’t on this list, very cool and simple carb.

Great article! We cover carburetors (with great affection!) at the Carburetor Appreciation Society:

Honestly, I didn’t read the whole article, but I think it’s probably just covering carbs that came on a production vehicle. If you get into the aftermarket I bet there’s tons of different wild designs.

A friend bought a Predator many years ago and tried it on his car (BBC). It ran well at full throttle but driveability was not good.

Never had any issues with SUs or Mikuni carbs. Like all carbs they need to be kept clean and tight. Adjustment on an established setup is not any different than setting idle screws on a two barrel. The supposed horrors of syncing multiple throats doesn’t exist if you approach with calm and reason. Can be perfectly synced with a drill bit or heavy wire mechanically or even by sight
without a vacuum gauge.

It’s too bad variable venturi carbs didn’t see greater use in America, a greater experience with them might have prevented some negative vibes.
The SU carb’s reputation undoubtedly was sullied by those more used to mechanisms of poor running associated with fixed venturi carbs. SUs - kept clean - are as close to set-and-forget as one could ask for. And with some modicum of understanding how they work, they’re not hard to set up.
My own long experience with these things is that distributor faults make their presence known long before the carbs complain in SU-equipped cars. But for mechanics weaned on the fixed venturi carb, the zillion intricate parts and passageways of the fixed venturi carb give problems before the diz can, so that’s of course why the attack on poor running was aimed at the carb for the mechanic used to American cars. The learned relationship of poor running with the carb meant those poor SUs suffered the attacks of the misdirected, when in fact the problem lay with ignition. Once meddled with, without an understanding of how they work it is indeed very difficult to tune them well. And then having created bad carb tuning, even if the diz is finally addressed, the engine still doesn’t run well because the SUs have been molested. A viscious cycle ensues, and hence a bad reputation for the SU and more generically for the cars that wore them.

I probably shouldn’t admit how many of those $5 Thermoquads I’ve bought and have stashed in my garage…

When they’re not ruined by a ham-handed rebuild, they’re probably the best, most accurate carburetor built prior to the really expensive Barry Grants, and even those probably aren’t as good at part throttle. And I’ve never had another carb I could pull off a stock 318 and plonk onto a 440 Magnum and have it just WORK. But all it takes is one over-tightened screw or X-section 0-ring improperly installed, and they become an efficient fuel “ejection” system.

The Holley 1904 and similar carbs gave the old teapots a run for the money on starting fires. They had a vertical seam at the fuel bowl joint. The bowl was a cheap casting which would warp and leak over time. Ford mounted this contraption on a “log” intake manifold located directly over the exhaust manifold on their small sixes. You could watch the gasoline “steam” coming off the manifold when the hood was up. In the Econoline vans, you could smell it if the engine compartment seals were worn.