Holley’s three-barrel existed within a small window of history where it was one of the meanest street carburetors you could get. Today, information on them is hard to come by.
For more than a decade, performance engines could be easily spotted by just a quick glance at their carburetor, or carburetors. When it came to American V-8-powered cars, economy models would typically sport a single two-barrel that would do its best to sip fuel. More performance-oriented models would include a four-barrel carb. Flashier models, from Oldsmobiles and Tri-Power Pontiacs to muscular FE Fords, big-block and small-block Mopars, and 427 Corvettes, flexed a trio of two-barrel carbs. Some cars even announced their performance with a pair of four barrels. Cadillacs, Chevy small-blocks, Super Duty Pontiacs, 7-litre Fords, and various brands of Chrysler Corporation cars used dual four-barrel carbs from the factory either inline or splayed on top of cross-ram intakes of various design.
By the late 1960s, GM was leaning away from multi-carb induction and banned any car but Corvette from using it. Even Chevrolet’s most potent big-blocks like the L88 and ZL1 relied on the simplicity of a single carburetor. Race sanctioning bodies like NASCAR were also mandating single four-barrel induction, leading to some ingenious solutions. It seemed that enthusiasts at the time were also more focused on single four-barrel street engines, jumping to dual four-barrel tunnel rams only for the ultimate in race performance.
The need for multiple carburetors was born from the simple demand of more airflow through the engine. Carburetors are rated for the amount of air they can get into an engine, and typical street V-8s run four-barrel carburetors in the 650–850 cubic feet per minute (CFM) range. If you want to make more power, whether by spinning the engine faster or by adding more displacement, the air has to come through the carb first.
Intake manifolds are made with the same basic carburetor flanges, with most aftermarket manifolds for performance use split into those that fit Holley’s popular 4150 and 4160 family or spread-bore flanges for Rochester’s Quadrajet and Carter’s Theromquad. There is only so much room to fit throttle bores on those predetermined flange dimensions, so in the late ’60s, Holley bridged the gap between the two secondary bores and created the 3160 family of carburetors with three barrels. Two models were available, with 950 and 1050 CFM ratings.
Contemporary aftermarket testing showed that these 950CFM three-barrels could eke out more power than the typical hot-rodder-favorite 780CFM Holley 4160, especially at higher engine speeds, simply by posing less of an airflow restriction. One of the downsides was its cost. In the vintage test we found in the September 1967 issue of HOT ROD, the 4160 four-barrel cost a paltry $80, while the three-barrel was $150. Adjusted for inflation, that would be more than $1100 today.
The single, wide secondary butterfly also posed some challenges. Many dual-plane manifolds feature a split plenum that would need to be modified to allow the secondary throttle plate to open. Edelbrock made an intake with these carbs in mind. Named C-3B for “Chevrolet three-barrel,” it came with the plenum divider milled down in the rear. The size of the secondary throttle blade also meant that a larger vacuum diaphragm was needed for it to open. The vacuum housing is larger in diameter than a soda can and an obvious clue that it isn’t your run-of-the-mill 750CFM Holley. If you need to rebuild one, good luck finding that secondary diaphragm; it seems they’re long out of production.
Compare the traditional Holley four-barrel vacuum diaphragm housing on the left to the three-barrel on the right.
These carburetors pop up on eBay fairly regularly, usually with “Hemi,” “Yenko,” or “Baldwin-Motion” in the title, but there’s not much information to be found on which tuners were installing them on their hot street packages.
Holley seemed to make its 3160 carbs obsolete with the introduction of the 4500 series carburetor in 1969. With a larger flange size, the 4500, known as the Dominator, could fit larger, 2.0-inch throttle bores and flow 1050CFM. It debuted in Ford’s NASCAR 429 that year and would be available over the counter in 1970 in various configurations. It became the carb of choice for high-horsepower street cars and drag racers due to its performance potential and, perhaps just as likely for many car builders, its menacing looks. An H.P. Books publication from 1976 titled Holley Carburetors & Manifolds doesn’t even mention the 3160, and information is hard to come by online.
The 3160’s large secondary may be a bit more prone to bogging down than your average Holley, but by many accounts, Holley’s three-barrel carb is just as easy to tune as its four-barrel brethren. They lend a great late-’60s look for a “day two” car, and for a mildly modified big-block with ported heads—and perhaps a roller cam—it might not be a bad choice. We’d think twice about grinding down any rare manifolds to make one fit though.
If anyone has any information sources on these carbs or if you have your own stories about running one, let us know in the comments below.