Cadillac’s Magnificent V-16 Engine: History, Photos, Specifications
How a legendary automotive powertrain came to be.
As the 1920s drew to a close, automakers were looking to make their products more powerful. Luxury cars were getting bigger and more opulent, high-speed highways were opening up, and motorists wanted to drive faster. Cadillac, already well-established as a luxury marque, had been using V-8 engines since 1915; in fact, it was the first automaker to field a successful mass-produced V-8. The company had just introduced its latest V-8 for the 1929 Series 341, a 5.6-liter (341 cubic inch) engine that delivered a stout 90 horsepower, and it had a 5.8-liter (353 cid) 95-hp engine in the works.
Still, the V-8 wasn't enough for what Cadillac had coming for 1930—a flagship model that was a foot longer and upwards of half a ton heavier and, by chief engineer William Strickland's estimates, would require at least a 40 percent power increase.
More Cylinders = More Power
Cadillac considered several options to increase power output. Superchargers were seen as racing accessories that were too temperamental. Adding a fourth gear to the transmission wouldn't yield enough of a real-world increase. Cadillac's engineers had experimented with different valve and head arrangements, but found they couldn't raise the engine's mean effective pressure without sacrificing low-RPM refinement.
Enlarging the V-8 presented several problems. Keeping the engine cool was one, and smoothness was another—Duesenberg was getting impressive power out of its straight-eight, but Strickland didn't think it delivered the refinement expected by Cadillac's clientele. Besides, a more powerful V-8 would require a new transmission and rear axle. Cadillac had just introduced its innovative new synchromesh transmission for 1929, and was concerned about reliability and refinement issues with a new gearbox.
The answer was to add more cylinders—a lot more. Doubling the number of pistons meant Cadillac could get the power it needed with a smaller per-cylinder displacement than the V-8. Decreasing the bore and stroke would allow the use of smaller and lighter pistons and connecting rods, which would in turn reduce vibration and internal stress, helping to ensure a long-lasting engine. Best yet, from a cost perspective, the torque characteristics of the V-16 meant that the engine could be paired with Cadillac's existing transmission and drive axle.
Cadillac intended the V-16 as a high-end engine for a halo car and, like several other luxury automakers, it was also developing a twelve-cylinder engine for introduction a year later. The V-12 had a larger cylinder bore than the V-16, but it shared much in the way of parts and technology with the bigger engine. And the V-12 served another purpose: Press leaks about it helped keep the V-16 a secret, not just from the public, but from lower-level GM staffers and suppliers as well. Many of the blueprints were stamped with "Bus" or "Coach", leading to speculation that Cadillac was doing engineering work for other General Motors divisions. When Cadillac launched the V-16 publicity blitz in December 1929, the public and the press were completely taken by surprise.
A Big New Car for Cadillac's Big New V-16 Engine
This monster of an engine was fitted to a monster of a car. The new model, called the V-16, had a 148-inch wheelbase (for comparison, the new-for-2021 Chevrolet Suburban's wheelbase is 134.1 inches), which was later extended to 154". The car had a three-speed synchronized transmission with a larger-diameter clutch than the V-8 cars. The mechanical brakes were cable-operated and aided by a vacuum booster. (General Motors would not switch to hydraulic brakes until later in the 1930s.) Prices started at $5,350 (about $82,000 in 2020 dollars) and could exceed $9,000 ($138,000).
The V-16 engine itself was an overhead-valve unit displacing 7.4 liters (452 cid) with a 3-inch bore and a 4-inch stroke. The 45-degree vee angle was chosen for chassis fit and serviceability. Engine structures at the time were usually multi-piece affairs, and the V-16 consisted of two V-8 cylinder blocks bolted to an aluminum-alloy crankcase. Cadillac had avoided straight-eight engines because of the concerns about harmonic vibrations with a long crankshaft, but the small bore meant the V-16 was reasonably compact—its five-bearing crank was actually slightly shorter than that of the contemporary Pierce-Arrow V-12. (Cadillac fitted a leaf-spring-type harmonic balancer, just in case.) Each bank had its own single-barrel updraft carburetor. The engine's aesthetics were as impressive as its engineering. All plumbing and wiring were concealed, and the engines were painted with black enamel trimmed with chrome and polished aluminum.
The engine was rated at 165 horsepower at 3,400 rpm, and was designed to operate reliably at the then-heady speed of 4,000 rpm. The V-16 developed 300 lb-ft of torque at idle, peak torque of 320 lb-ft @ 1,400 rpm, and more than 300 lb-ft from 400 rpm to 2,000 rpm. One British magazine found that the car could be shifted into top gear at 2.5 MPH and accelerated smoothly to top speed—which, depending on the gearing and body fitted, ranged from 84 to 91 mph, with roadster bodies reportedly topping 100 mph.
V-16 Power Requires Cadillac Refinement
The Cadillac V-16's best attribute wasn't so much power as it was refinement. Valvetrain noise was the biggest issue with overhead-valve engines, so Cadillac developed an industry-first hydraulic lash adjuster (though of a different sort than the hydraulic tappets common today). According to Cadillac, the engine was so smooth and quiet that at idle you could hear the clicking of the ignition points in the distributor. Reviewers marveled at the car's speed, serenity, and smoothness. In terms of performance, the Duesenberg Model J was the only contemporary car that could top it, and the Duesey achieved its superior speeds at the expense of inferior refinement.
For a halo car, sales were surprisingly strong. Cars were in dealerships by the spring of 1930, and in the first two months of sale the V-16 cars accounted for some 20 percent of Cadillac's sales, far more than GM expected. But the Great Depression was taking hold, and the introduction of the 135-hp V-12 engine in 1931, fitted to a smaller chassis, impacted V-16 sales. Cadillac sold 2,887 V-16 cars for 1930, but only 750 in 1931, more than half of which were leftover 1930s—only 364 V-16s were produced in 1931. Sales continued to drop, with only 212 cars built between 1935 and 1937. (The V-16 car was renamed Series 90 in 1936.) In 1937, the V-12 engine outsold the V-16 10 to 1. Cadillac made few changes to the engine in this period, upping horsepower to 185 in 1934, with the V-12 increasing to 150 hp the same year.
Surprise, Surprise: A New V-16 for 1938
With sales down to a trickle, it was expected that Cadillac would kill the V-16 engine, but instead the company shocked the industry by introducing a new version in 1938. This was a completely different engine with a 135-degree angle between the cylinder banks, so wide that the engine looked more like a flat-16 than a V-16. Bore and stroke were both 3.25 inches, resulting in a displacement of 7.1 liters (431 cid). The crankshaft now had nine main bearings, and instead of overhead valves it used a flathead arrangement. The new engine was 250 lb lighter, six inches shorter front-to-back, and a whopping 13 inches lower from top to bottom, a boon to the lower hood lines then coming into vogue. Though its maximum engine speed was lower, it produced the same 185 horsepower as its predecessor and featured the same silent, smooth operation. The new V-16 could easily propel the Series 90 to speeds in excess of 100 mph.
Aesthetically, the engine was short and squat and fell far short of the beauty of the 452. Whereas the older V-16 had most of its wiring and plumbing concealed, the new V-16 did away with such frivolities, which was one of many changes intended to make the engine cheaper to produce and easier to service. This has led many collectors to deem the flathead engine inferior to the overhead valve engine, though it greatly improved acceleration.
Cadillac produced the new engine for the 1938, '39, and '40 model years, but only sold 508. Production of both the car and the engine ceased in December 1939.
The V-16 Lives On in the New Millennium
As it happens, the 431 was not the last Cadillac V-16. At the 2003 New York International Auto Show, Cadillac unveiled the gigantic Sixteen concept car, powered by a 13.6-liter naturally-aspirated V-16 engine said to produce 1,000 horsepower and 1,000 lb-ft of torque. The concept was drivable; in fact our sister publication MotorTrend reviewed it and James May drove it on Top Gear (Season 2, Episode 10). Cadillac apparently had intended a production version, but it was scuttled by the 2008 bankruptcy.
Today, the original Cadillac V-16 remains a highly sought-after collectible and one of the most revered American cars of its era. It has been argued that the V-16 was not a success, as sales were limited and Cadillac reportedly lost money on every one it built. Even so, the V-16—car and engine—was a triumph that solidified Cadillac's reputation as one of the world's finest motor cars and a true Standard of the World, a reputation that would remain largely untarnished until the 1980s.
1930 Cadillac V-16 Engine Specifications
- Years produced: 1929-1937
- Bore x stroke: 3" x 4"
- Displacement: 7.4L, 452 cid
- Valvetrain: Overhead, 2 valves/cyl
- Power output: 165-185 hp, 320 lb-ft
- Used in: 1930-1935 Cadillac V-16, 1936-1937 Cadillac Series 90
1938 Cadillac V-16 Engine Specifications
- Years produced: 1938-1939
- Bore x stroke: 3.25" x 3.25"
- Displacement: 7.1L, 431 cid
- Valvetrain: L-head, 2 valves/cyl
- Power output: 185 hp
- Used in: 1938-1940 Cadillac Series 90
2003 Cadillac V-16 Engine Specifications
- Years produced: 2003
- Displacement: 13.6L, 829 cid
- Valvetrain: Overhead, 2 valves/cyl
- Power output: 1000 hp, 1000 lb-ft
- Used in: 2003 Cadillac Sixteen concept