The Ford flathead V8 (often called simply the Ford flathead, flathead Ford, or simply flatty, when the context is implicit, such as in hot-rodding) was a flathead V8 engine designed by the Ford Motor Company and built by Ford and various licensees. During the engine's first decade of production, when overhead-valve engines were rare, it was usually known simply as the Ford V‑8, and the first car model in which it was installed, the Model 18, was (and still is) often called simply the "Ford V‑8", after its new engine. When the engine was introduced in 1932, it was a market first in several respects: in cars that were affordable to the emerging mass market consumer, it was the first 8-cylinder, the first V8, and the first V engine to become widely available in automobiles. It was the first independently designed and built V8 engine produced by Ford for mass production, and it ranks as one of the company's most important developments. A fascination with ever-more-powerful engines was perhaps the most salient aspect of the American car and truck market for a half century, from 1923 until 1973. The Ford flathead V8 was perfectly in tune with the cultural moment of its introduction, leading the way into a future of which the Ford company was a principal architect. Thus it became a phenomenal success. The engine design, with various changes but no major ones, was installed in Ford passenger cars and trucks until 1953, making the engine's 21-year production run for the U.S. consumer market longer than the 19-year run of the Ford Model T engine for that market. The engine was on Ward's list of the 10 best engines of the 20th century. It was a staple of hot rodders in the 1950s, and it remains famous in the classic car hobbies even today, despite the huge variety of other popular V8s that followed.
Before this engine's introduction, almost all mass-produced cars affordable to the "average mass-market consumer" (which was a concept that Ford helped invent) used straight-4 and straight-6 engines. Multi-cylinder V-engines (V8s, V12s and even V16s) were produced, but they were not intended for mass production and were generally used in luxury models.
Even though Ford had an engineering team assigned to develop the engine, many of the ideas and innovations were Henry Ford's. The Model A, its variants (B and 18), and this V8 engine were developed between 1926 and 1932, and this period was the elder Ford's last central contribution to the company's engineering. He remained an innovator until his death, but his later ideas were not immediately central to the company's business.
This design had the camshaft above the crankshaft, as in the later pushrod operated overhead-valve engine. Valves for each bank were mounted inside the triangular area formed by the "Vee" of cylinders. The intake manifold fed both banks from inside the Vee but the exhaust had to pass between the cylinders to reach the outboard exhaust manifolds. Such an arrangement transferred exhaust heat to the block, imposing a large cooling load; it required far more coolant and radiator capacity than equivalent overhead-valve V8 engines. Ford flathead V8s were notorious for cracking blocks if their barely adequate cooling systems were overtaxed (such as in trucking or racing). The simple design left much room for improvement, and the power available after even low cost modifications was usually substantially more than could be obtained from an overhead-valve inline six-cylinder engine of similar displacement.
The Ford flathead V8 was licensed to other producers. It was used by Simca in France until 1961 and in Brazil until 1964 for cars and until 1990 in the Simca Unic Marmon Bocquet military truck. In the United States, the flathead V8 was replaced by the more modern overhead-valve Ford Y-block engine in 1954.
The crankshaft development for the Ford flathead V8 was pioneering. The engine's production development program began with a forged steel crank, per conventional practice, but Ford then developed the improved foundry practice, heat-treating, and materials handling logistics to make the cranks from cast steel instead, yielding in the end a crank just as strong, but less expensive to produce. These new methods were patented.
A simple three-main-bearing crankshaft used the common V8 practice of using each throw for two connecting rod big ends, one for each bank.
The short crankshaft proved quite durable in comparison to six-cylinder engines when roughly handled. For these reasons, the flathead Ford became a favorite among hot-rodders, and this in turn led to a rich supply of aftermarket performance parts. With the use of specialized pistons or connecting rods the stroke of the crankshaft could be increased by welding and regrinding as a method of increasing engine displacement, usually in combination with overboring as described below.
The sought-after crankshaft by hot rodders is the four-inch (101.6 mm) stroke Mercury version. It can be identified by the clean-out plug in the front of the crankshaft. It measures 5/8" on the Mercury crankshaft and 3/8" on the 33⁄4" Ford crankshaft. These 4" crankshafts came in the 1949 to 1953 engines.
One of the most important innovations in the Ford flathead V8 was the casting of the crankcase and all 8 cylinders in one engine block. This level of monobloc design for V-8 blocks had been accomplished before, but it had never seen mass production. Making it practical for the latter was an example of the production development needed to bring a V8 engine to the widely affordable segment of the market. Most V engines of the time had multiple cylinder blocks bolted to a common crankcase (itself a separate casting). At most, each bank of the V was an integral block, but many V engines had 4- or even 6-cylinder blocks, with cylinders cast in pairs or triples. Like most other engine blocks then and now, it was cast iron; but the foundry practice (e.g., workflows, materials handling) was a revolutionary advancement in the mass production of castings. Charles E. Sorensen lived up to his longtime nickname at Ford, "Cast-Iron Charlie", by leading this revolution to bring Ford's first V8 to market.
As with any V8, the block was relatively light for the displacement supported. The bottom of the block formed the parting line for the main bearing caps. The most complex part of the block was the exhaust passage routing. The exhaust valves were on the inside of the V and exhaust flow was initially downward and passed around the cylinders through the water jacket to exit on the outside of the cylinder block. The routing of the exhaust through the water jacket put an extremely heavy load on the cooling system and led to frequent overheating, especially on early models, if the cooling system were not maintained. Somewhat primitive water pumps used until the advent of the 1948 8RT and 1949 8BA models also contributed to the overheating problem. The space for the exhaust flow was also somewhat restricted, so the exhaust passages were tall and narrow in some locations. The gas flow past the rough sand castings could be greatly improved by polishing the passages. The capacity of the block for over-boring (beyond normal boring for wear compensation) was limited by the configuration and the metal available. In early blocks, some cylinder walls were extremely thin due to cores shifting during casting. It was prudent to overbore before relieving and polishing the ports, as a casting flaw such as a sand pit might be revealed, usually fatal to further use of the block. The blocks with the factory 3-3⁄16 (3.1875) inch bore can usually be safely bored 1/8 inch over standard to 3.3125 inches (84.14 mm) and sometimes can be bored 3/16 inch over standard to 3.375 inches (85.7 mm), increasing displacement a little over 12%.
The engine built from 1932 to 1935 had poured main bearings which required skill and machine shop equipment to overhaul. Part of the 1936 production and all production from 1937 to the end of flathead V8 production had both replaceable shell main bearings and connecting rod inserts (unlike the contemporary GM products), enabling straightforward and low cost rebuilding, another reason why the Ford was a favorite of amateur mechanics.
Also unlike the Chevrolet inline 6, Ford products used high oil pressure for lubrication for the main and rod bearings, as do all modern vehicle combustion engines. While this offered no special performance advantage it did eliminate a complex oil jet system in the oil pan. As a side benefit to a prospective purchaser of a used vehicle, this also enabled the condition of the connecting rod and main bearings to be determined indirectly by observation of the analog oil pressure gauge after the vehicle was warmed up, provided that oil of normal viscosity was in use.
The left side exhaust manifold exhausted to the front, where a crossover pipe took the exhaust to the forward end of the right side manifold on the car engines and between the 1st and second cylinder on some trucks, in turn exhausting to a single pipe at the rear. A common conversion was to block off the right forward manifold entrance and route the left side exhaust to a new pipe to form a dual exhaust system with better flow characteristics. These typically involved installation of free-flowing mufflers, which if at a legal noise level still allowed low frequency sounds to pass, giving a characteristic rumbling dual exhaust sound to these systems. In the 1950s shortcut exhaust outlets with manually removed covers were added to street machines in emulation of vehicles intended for high speed straight line racing on dry lake beds, typically located just behind the front wheel, although chromed external runners sometimes extended to just forward of the rear wheel. These covers were referred to as lake plugs, the pipes as lake pipes. This style exhaust was also used legally in sanctioned drag racing and illegally in unsanctioned performance demonstrations.
Internal fuel flow
More extreme modifications were to improve the airflow by removing material from the top of the block between the valves and the cylinders (called relieving), increasing the size of the inlet and exhaust passages (called porting), and by polishing the sand-cast surfaces to improve fuel flow. Increased compression ratios could be cheaply obtained by milling material from the head or by obtaining aluminum heads as aftermarket parts. Higher capacity intake manifolds were similarly available. Changing the camshaft to a higher performance version required head removal so that the valves could be held up out of the way, so this was usually done only as part of a substantial rework of the basic engine.
A popular modification for the flathead was conversion to an overhead-valve configuration, and many such modification kits were available, including the Ardun heads from Zora Arkus-Duntov who was to go on to fame as the "father of the Corvette". These conversions were not initially demanded by hot rodders looking for extra power, as they had not yet exhausted the capabilities of the flathead configuration, but were demanded by users of the engine in trucks and other such high load applications, where the constant flow of hot exhaust through the block to the exhaust manifolds caused the entire engine to overheat; the overhead-valve heads routed the exhaust out more directly, and away from the block.
Modern performance flatheads
Ford flatheads are still hot rodded today, with a special land speed record class for flathead engines. The current record holder achieves 700 hp (525 kW) and 300 mph (483 km/h). Note that on one pass the car broke 300 mph (480 km/h) but did not set a record. Two passes have to be made in order to break the record.
Types are classified by their displacement.
The original flathead engine displaced 221 cu in (3.6 L), with 3.0625 by 3.75 in (77.79 by 95.25 mm) bore and stroke. The block was cast as a single piece (monobloc) for durability, and a single-barrel carburetor fed the engine. The 1932 V8-18 with 5.5:1 compression produced 65 hp. The 1933-34 V8-40 raised compression to 6.33:1 and power to 75 hp (56 kW). In 1934 a two barrel down draft carburetor was introduced. 1935's V8-48 saw compression drop to 6.3:1, but power climb to 85 hp (63 kW), and torque was rated at 144 lb·ft (195 N·m). It became the V8-68 in 1936, with compression, horsepower, and torque unchanged.
Production of the original 221 lasted from 1932 through to 1936. These engines can be identified by having the water pumps located at the front of the heads. A similar 221 flathead was used in Fords for 1937 and 1938 but the block was revised to have the water pumps mount to the block. The new design also relocated the water outlet from the front of the heads to the top center of the heads. These, designated V8-78, were offered with standard 6.2:1 compression aluminum or 7.5:1 compression iron cylinder heads, rated at 85 hp (63 kW) and 144 lb·ft (195 N·m) (aluminum) or 94 hp (70 kW) (iron). The 1932 through 1938 motors used twenty one studs to hold down each head and are known as "21 stud" motors. This motor continued to be made into the 1950s in Europe.
In late 1938 Ford introduced V8-81A, commonly called the "24 stud" engine because it uses twenty four studs to hold down each head. This engine debuted at the same time as the 239 motor. With 6.12:1 compression, horsepower remained the same, but torque increased by 2 lb·ft (2.7 N·m). In 1939, as the V8-91A, compression increased to 6.15:1, power rose to 90 hp (67 kW), and torque reached 155 lb·ft (210 N·m); the ratings remained the same for the 1940 V8-01A, 1941 V8-11A, and the last civilian model, the V8-21A, which saw compression rise, to 6.2:1. This engine was used through 1942 for civilian use and saw some use in military vehicles during World War Two. Collectively all 221 motors are commonly referred to as "85 horse" motors.
Ford introduced the 239 cu in (3.9 L) V8-99A engine, with 3.1875 by 3.75 in (80.96 by 95.25 mm) bore and stroke and 6.15:1 compression, in 1939. It produced 95 hp (71 kW) and 170 lb·ft (230 N·m). This was done to provide a more powerful engine for the Mercury cars, which Ford Motor Company started making in 1939. It was used in Mercurys in 1939 and in Fords in 1946. This engine is very similar to the late 221 engine. As the V8-09A in 1940, compression, power, and torque were unchanged; in 1941, the V8-19A compression and power were static, but torque rose by 6 lb·ft (8.1 N·m), while the 1942 V8-29A increased compression to 6.4:1 and power to 100 hp (75 kW), while torque stayed the same. Postwar, it became the V8-69 (suffixed "A" in Fords, "M" in Mercurys), with compression 6.75:1, 100 hp (75 kW), and 180 lb·ft (240 N·m). For 1947 and 1948, only the designation changed, to V8-79 and -89. The 239 was redesigned in 1948 as the 8RT for Ford trucks and in 1949 as the 8BA for the cars. It had higher 6.8:1 compression, but performance was unchanged. The 1950 V8-0BA boosted torque by 1 lb·ft (1.4 N·m), the 1951 -1BA by 6 lb·ft (8.1 N·m) more, while in 1952, as the V8-B2, compression climbed to 7.2:1, power to 110 hp (82 kW), and torque to 194 lb·ft (263 N·m), then to 196 lb·ft (266 N·m) in the -B3 of 1953, its final year. The 1948 to 1953 engines have a revised cooling and ignition system. Collectively all 239 engines are referred to as "100 horse" engines, although the horsepower was increased in 1952 to 110 horsepower in cars and 106 horsepower in trucks. This engine was used in Ford's transit buses during their short stint in the transit bus business from the late 1930s to the early 1950s.
The latest iteration of this engine, used from 1948 to 1953, was initially designated the 8BA (see above) in automobiles and the 8RT in trucks. 8RT remained the truck engine designation throughout the entire run from 1948 through 1953. They were essentially identical. Earlier Ford V8s had the unique Ford designed distributor driven directly from the forward end of the camshaft, which was an inconvenient location for maintenance. This final flathead used a more conventional distributor driven at a right angle to the crankshaft and located at the right front of the engine where it was readily accessible. The water inlets and thermostat housings were moved to the front end of the heads, and the 24 studs and nuts that attached the heads on the old engine were replaced by 24 bolts.
A 136 cu in (2.2 L) V8-74 version was introduced in the United States in 1937. With 2.6 by 3.2 in (66 by 81 mm) bore and stroke and 6.6:1 compression, the engine was rated 60 hp (45 kW) and 94 lb·ft (127 N·m). The designation changed again in 1939, to V8-922A, but the specifications remained the same. It was produced in Europe in 1935 and 1936, and was used in the many standard Ford vehicles based on the car platform of the era. It was not very popular with U.S. buyers who were used to the 85 horsepower (63 kW) cars. Redesignated V8-82A in 1938, V8-922A in 1939, and V8-022A in 1940, compression, power, and torque remained unchanged. The engine was very popular as a powerplant for midget race cars after World War II. This engine is most commonly referred to as the "60 horse" flathead, or the V8-60. It was replaced by the 226 straight-6 in the 1941 Fords, though it would continue to be used after the war in the French Ford Vedette.
The 1948–1953 255 cu in (4.2 L), referred to as the model BG, was achieved by use of a 4-inch (100 mm) stroke crankshaft in the 239 cu in (3.9 l) 8BA/8RT engine. It was only used in Mercury cars, and heavy service trucks. Known as the V8-9CM in 1949, it featured 6.8:1 compression, 110 hp (82 kW), and 200 lb·ft (270 N·m) torque, which stayed the same for the 1950 V8-0CM. The 1951 V8-1CM raised this by 2 hp (1.5 kW), and 6 lb·ft (8.1 N·m) torque, The 1952 V8-MA boosted compression to 7.2:1, power to 125 hp (93 kW), and torque to 218 lb·ft (296 N·m), while only the name changed, dropping the -MA, for the last year of production, 1953.
Because of interchangeability, the Mercury crank made a popular upgrade in the 239 among hot rodders, much as the 400 cu in (6.6 l) crank was in Chevrolet small-blocks. In fact, in the 1950s, the flathead block was often fitted with crankshafts of up to 4.125 in (104.8 mm) stroke. In addition, rodders in the 1950s routinely bored them out by 0.1875 in (4.76 mm) (to 3.375 in (85.7 mm)).
The largest displacement version (at 337 cubic inches/5.5 litres) of the production Ford flathead V8 engine was designed for large truck service. When Lincoln could not produce the V12 engine it wanted for the 1949 model year, the 337 motor was adapted for passenger car use. The 337 features a 3.5 in (88.9 mm) bore and a 4.375 in (111.1 mm) stroke.
It was introduced in the 1948 two and a half ton and three ton Ford trucks and the 1949 Lincoln passenger cars. It was produced through the 1951 model year. In 1952 it was replaced in the Lincoln passenger cars and Ford three ton trucks with the Lincoln Y-block 317 cu in (5.2 L) overhead-valve V8. The two and a half ton Ford trucks got a 279 cu in (4.6 L) version of the 317 motor.
- Sorensen 1956, p. 231.
- Sorensen 1956, p. 229.
- Sorensen 1956, p. 225.
- George McNicholl (2005-10-01). How to Build Ford Flathead V-8 Horsepower. pp. 77–78. ISBN 0-7603-2290-2.
- Sorensen 1956, pp. 230–231.
- Editorial staff (1916), "Pennsylvania S.A.E. section formally organized and holds first professional session", Automobile Trade Journal 20: 101A–103.
- Sorensen 1956, pp. 107,227–231.
- "Announcing the Reintroduction of the ARDUN OHV Cylinder Head." ardun.com, 1 July 2008
- "Flatfire Racer Sets 300 Miles per Hour Record at Bonneville Salt Flats 2004 Using 1946 Ford Flathead Engine; Ron Main Speed Ace on Land." bluebird-electric.net, 7 October 2006.
- Street Rodder, 1/85, p. 73
- Street Rodder, 1/85, p. 72.
- Sorensen, Charles E.; with Williamson, Samuel T. (1956), My Forty Years with Ford, New York, New York, USA: Norton, LCCN 56010854. Various republications, including ISBN 9780814332795.
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