Ford Flathead Engine
Overview
This design had the camshaft above the crankshaft, as in a modern 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 V-8 engines. 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. Flatheads are notorious for cracking blocks due to inadequate cooling systems.
Crankshaft
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 (102 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 3 3/4″ Ford crankshaft. These 4″ crankshafts came in the 1949 to 1953 engines.
Block
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. As the exhaust valves were on the inside of the V and exhaust flow was initially downward, the path had to pass around the cylinders. Since each cylinder was also surrounded by a water jacket, the space for the exhaust flow was 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 overboring (beyond normal boring for wear compensation) was limited by the configuration and the metal available. 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%.
Bearings
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.
Lubrication
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.
Exhaust
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, 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 gas flow
More extreme modifications were to improve the airflow by removing material from top 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 gas 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.
Overhead valve kits
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.
Version types
Flathead V8 in a 1937 Ford coupe
Types are classified by their displacement.
221
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.[citation needed] 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 lbft (195 Nm). 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 lbft (195 Nm) (aluminum) or 94 hp (70 kW) (iron). Output was 85 hp (63 kW). 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 lbft (2.7 Nm). In 1939, as the V8-91A, compression increased to 6.15:1, power rose to 90 hp (67 kW), and torque reached 155 lbft (210 Nm); 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.
239
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 lbft (230 Nm). 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 lbft (8.1 Nm), 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 lbft (240 Nm). For 1947 and 1948, only the designation changed, to V8-79 and -89. The 239 was redesigned in 1948 for Ford trucks and 1949 for the cars. Identified as the V8-8BA for 1949, it had higher 6.8:1 compression, but performance was unchanged. The 1950 V8-0BA boosted torque by 1 lbft (1.4 Nm), the 1951 -1BA by 6 lbft (8.1 Nm) more, while in 1952, as the V8-B2, compression climbed to 7.2:1, power to 110 hp (82 kW),and torque to 194 lbft (263 Nm), then to 196 lbft (266 Nm) 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 designated the 8BA in automobiles and the 8RT in trucks. 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.
136
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 lbft (127 Nm). 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.
255
The 1948-1953 255 cu in (4.2 L), referred to as the model BG,[citation needed] 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. Known as the V8-9CM in 1949, it featured 6.8:1 compression, 110 hp (82 kW), and 200 lbft (270 Nm) torque, which stayed the same for the 1950 V8-0CM. The 1951 V8-1CM raised this by 2 hp (1.5 kW), and 6 lbft (8.1 Nm) torque, The 1952 V8-MA boosted compression to 7.2:1, power to 125 hp (93 kW), and torque to 218 lbft (296 Nm), 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 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)).
337
This motor 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.
In the song “Hot Rod Lincoln,” the engine referred to in the original lyrics was a Lincoln V-12 not mentioned in the Commander Cody version.
See also
List of Ford engines
References
^ “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.
^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah Street Rodder, 1/85, p. 73
^ a b Street Rodder, 1/85, p.72.
External links
Watch As We Build A Flathead Powered Roadster
Newly Engineered Flathead Block
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