Ford’s Famous Flathead

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by Huw Evans  More from Author

A Look at Hot Rodding’s Pioneering Powerplant

Photos by Huw Evans and courtesy of Richard Willim.

It wasn’t the biggest, the most powerful, or the most glamorous, yet in the world of hot rodding, Ford’s venerable L-head V-8, better known as the “flathead,” helped introduce the concept of low buck performance and parts interchangeability, creating a car culture revolution in the process. In this article, we highlight some features of this venerable V-8 and discover some little known facts as well as a few hot rodding tips.


Like many great automotive ideas, the Ford L-head V-8 (Ford never officially called it the flathead) had a troubled birth. According to Roy Nacewicz, noted flathead historian, “There were a lot of problems in the early days. That was part of the reason why the 1932 Ford Model B (four-cylinder) was kept in production. Ford didn’t have any V-8s available until April of 1932, which made for a very short model year for the Model 18. With a network of 7,000 dealers in the US, only 700 were able to get V-8 cars – others had to make do with large artwork drapes of them which they hung in the showroom, and even then, there was no guarantee that interested customers would be able to get a car during the model year. As a result, many ended up buying Model Bs, simply because the four-cylinder engines were stockpiled. In fact there were so many four-cylinder engines that Ford stashed them wherever it could, in warehouses, boxcars – some were even placed in the lobby of World Headquarters on Schaffer Road.”

But in the context of the time, perhaps it wasn’t surprising that Ford’s new V-8 had a difficult start – after all, it was a fairly ambitious project. “Rival manufacturers were introducing more in-line six-cylinder engines,” says Nacewicz, “and Henry Ford wasn’t too fond of them. Always looking for a way to one-up the competition, especially Chevrolet, he saw an eight-cylinder engine as the solution. You also have to remember that at that time, cylinders sold, so the more an engine had, the better it was perceived to be. That’s why luxury cars employed straight eights (Buick, Packard), or in some cases even V-16s (like Cadillac).” However, in order to fit an eight-cylinder engine in an existing Ford design, compactness was essential. “That’s basically why Ford went with a V-configuration,” says Nacewicz. But the process of developing such an engine proved rather tricky at first.

“Ford assigned two teams to work on the project – one that was an official group working inside Ford engineering, and the other, which was pretty much a top-secret affair. The former group, which started first, wasn’t very successful. When it came to metallurgy, they simply couldn’t find a way to cast the block in one piece – they tried multiple times and couldn’t make it work.” Ol’ Henry, fed up with the lack of progress, decided to put together a skunk works operation in the old Thomas Edison Fort Myers laboratory that he had purchased and relocated to Dearborn (what is now Greenfield Village). “There were these five guys, who were essentially told to develop this new engine,” says Roy. “The program was so secret that Ford had them collected from their houses in chauffeur-driven cars – they were handpicked by the old man himself and were engineers he trusted. It was these guys who developed what we know today as the flathead V-8.”

Original Features

The original 221 cubic-inch L-head V-8 engine was an undersquare design, boasting a 3.16-inch bore and 3.34-inch stroke. The block was essentially the forerunner of most modern, mass-produced V-8 engines, with the bottom of the block creating a parting line for the main bearing caps and the camshaft housed in the top of the Vee with valves inside of each bank. Although it had double the amount of cylinders over the existing four, the new V-8 was heavy – around 122 pounds heavier, fully dressed (a total weight of 571 lbs. dry). Although the block was made from cast iron, due to metallurgy technology at the time, it had some interesting features.

Says Richard Willim, a long time flathead engine builder and hydroplane racer, “Because it took so long to develop a process to effectively cast the block in one piece, Henry Ford wanted to ensure that the engines would last. He was concerned that the relative softness of the iron available would cause premature wear on the cylinder walls, so the early engines had stainless steel sleeves around the bores. It’s a very unique design, and it looks like it’s stitch-welded – uniform all the way around the bore. As for how it was originally installed, that remains a mystery, though the consensus is that it was either rolled or fused together at the same time around each bore.”

In its debut, 221ci configuration, the original L-head V-8 was rated at 65 horsepower at 3500 rpm and 125 lb-ft of torque at 1400 revs. “It really was a high performance engine in its day,” remarks Nacewicz. “To have that kind of torque in a low priced car was quite a revelation back then.” But Henry Ford, as always, was more concerned about cost and mass-production than the flathead’s status as a performance standard bearer. “The engine was designed to be geared for mass production, which meant it broke new ground in several ways,” says Roy. “Many of the parts were interchangeable – part of the reason that it became so popular in later years.” However, there were some issues that surfaced. The early engines (1932-35) featured three main bearing crankshafts with poured Babbit bearings and only on the mains, not the rods. As Richard Willim notes, “It was very difficult to replace the bearings on these early cranks and required the services of skilled machinists, because Babbit was very difficult to pour.”

Another interesting feature was the exhaust design. “The exhaust valves were positioned inside of the V of the block. The flow of the spent gases was therefore drawn downwards and close to the cylinders, which restricted flow.” Also because the hot exhaust gas flowed so close to the water jacket, overheating was a problem, not helped by a central exhaust port for the middle two cylinders  (2/3 and 6/7) on each side. “This was something that was never fully addressed,” says Roy, “from the first 221, 65 horsepower version to the ultimate 255 cubic-inch unit found in 1950-53 Ford passenger cars – it was an inherent problem in the design of the engine.”

The valvetrain was also quite unique. “When you look at a flathead,” says Richard Willim, “you’ll notice that the crank and camshaft are not in-line. The center of the crank is actually offset, and the angle of the valves relative to the camshaft are different on both sides, so as a result you have four ports that are shorter and four that are longer. That means you get four cylinders for low-end torque and four for higher-end power.” Back in 1932, that was a huge advantage in the low priced market, especially in a car like a relatively bantamweight Ford Model 18 three-window business coupe.

“Part of the original group of five who worked in secrecy on the L-head V-8 was a guy by the name of Don Sullivan,” says Nacewicz. “He did a lot of experimentation, trying different valve angles and camshaft designs on the engine, but with the flathead, developing a compromise between smooth running and high performance was always a tough balancing act.” Indeed, the early flatheads, although much smoother than contemporary four or even six-cylinder engines, were still gruff in some regards – a rough idle being one of them. “The engines that actually made it into ’32 model year cars featured a single barrel carburetor, built by the Detroit Lubricator company,” mentions Roy. “For the time, it was actually an advanced design – a variable venturi that altered the flow of the air into the intake, but the downside was a rough idle on the factory-built engines. In 1934, Ford adopted a new carburetor – a two-barrel design from the Stromberg Company in Indiana, the model 48. This gave better throttle response and a much smoother idle.” The flathead was on its way to greatness.


Aside from the fuel system, changes were relatively few to the L-head through 1935, though in 1933, compression was raised to 6.33:1 and Ford revised power output, rating the L-head V-8 at 75 horsepower. However, on reflection, it appears this might have been optimistic, as Roy Nacewicz relates. “Given the technology available at the time, it’s actually quite difficult to believe that this engine could have received a 10 horsepower jump in such a short space of time. One logical explanation is that the ’32 engines were underrated and the ’33 version overrated. There’s probably traction to this argument due to the very late introduction and availability problems with the ’32 engines. You have to remember, it was a daring design at the time, and production delays meant that the public was quite skeptical. For the 1933 model year, many of those problems were overcome, so perhaps Ford could be more confident – hence the significant jump in output.”

In 1935, Ford lowered compression to 6.3:1, but power output was raised again – jumping another 10 horses for a total of 85 hp. However, it was during this year that a significant change took place – one that would turn the flathead into a backyard mechanic’s (and later, hot rodder’s) friend. “It was the bottom end, specifically the crank and bearings,” says Roy. “Ford finally decided to eliminate the Babbit bearings, instead adopting removable inserts for both the crankshaft and rods. This meant that average guys – backyard mechanics – could now easily rebuild these engines at fairly low cost.” A revolution had begun.

Most sources indicate that the new bearing design was introduced on 1936 series production engines, though not all passenger car units received the change until the 1937 model year. An interesting aspect was also the oiling system. “Part of the reason why the flathead was so suited to mass production, “ says Nacewicz, “was the fact that it used high pressure to lube the main and rod bearings, without requiring oil jets in the sump. In this aspect, it was quite ingenious and far ahead of what else was being offered at the time, particularly from archrival Chevrolet. In fact, when Chevy finally introduced its own V-8, the overhead-valve 265ci small-block in 1955, it adopted an oiling system very similar to the flathead.”

During 1937, other changes were introduced. “The cooling system was revised,” says Roy. “On the early engines, the water pump was mounted to the front of the heads. Starting in 1937, a new design was used in which the pump mounted to the block and the water passages were moved from the front to the top center of the cylinder heads. This version of the engine, still a 221ci unit, was known as the V8-78 and rated at 85 horsepower, still using a Stromberg 48 two-barrel carburetor. The following year, further changes were instigated, actually resulting in a designation change (V8-81A). “This engine had different pistons and actually lower compression (6.12:1),” says Nacewicz, “but perhaps the most noticeable external difference were the cylinder heads. This engine used 24 externally mounted studs on each head, instead of 21 found on the earlier L-head Ford V-8s.” It was this version of the flathead that became synonymous with hot rodders in the post war period and, for traditionalists, still remains so today.

For the 1939 model year, Ford bumped the compression slightly to 6.15:1, resulting in a slight power hike to 90 hp and 155 lb-ft of torque, where it would remain through 1941. “Ford actually raised compression on this engine to 6.2:1 for 1942,” mentions Nacewicz, “but not that many were built for civilian use, because wartime halted production.” Nevertheless the V-8 21A, as the 1942 version was called, saw use in military vehicles, including landing craft and light armored carriers. The 21A was also the last of the 221ci motors. After the war, Ford adopted a larger 239ci version that was originally introduced for Mercury passenger cars, beginning with the 1939 model year.

Mercury Flatheads

“Ford had identified a gap in the market for a mid-priced car,” remarks Nacewicz. “But because it was a larger, more up-market vehicle, it was deemed necessary to fit a bigger, more powerful engine, so Ford took the 221 and enlarged the bore to 3.18 inches, resulting in a 239ci engine. When it was launched, this engine was rated at 95 hp and 170 lb-ft of torque, but horsepower climbed to 100 hp in 1942.” Yet in order to save costs on tooling, a lot of parts were interchangeable with the post-1937 221, which would prove a benefit to hot rodders, especially during the postwar period. The 239 was also remarkably long lived, enduring all the way to the end of flathead production in 1953.

“In the postwar years, it received a number of improvements,” says Roy. “It was significantly redesigned for 1948 with a revised cooling system, with the water inlets and thermostat housings moved from the center to the front of the heads - the studs were also substituted for bolts.” Another change was the distributor. “Earlier flatheads used a ‘crab’ distributor. It was located down on the front of the engine, and it wasn’t easy to get to for servicing. Ford finally addressed this problem by mounting a conventional distributor, 90 degrees to the crankshaft on the right side of the engine. Besides Ford and Mercury passenger cars, this engine was also used in light trucks, including the new-for-’48 F-series pickups and panel vans.”

Perhaps even more significant from a hot rodder’s standpoint was the introduction of a 255ci Mercury flathead in 1948. “This engine used the 239ci block, but it employed a crankshaft with a longer 4-inch stroke,” says Roy, “so although it was rated at 100 hp when installed in the redesigned 1949 ‘bathtub’ Mercury, it produced 200 lb-ft of torque, which was necessary to get these heavy cars moving. Also, by flathead standards, it had a fairly high compression ratio – 6.8:1.” And things would only get better. Power was up to 102 hp and 206 lb-ft by 1951, and when Ford and Mercury passenger cars were re-bodied again for 1952, the 255 received a further hike in compression – up to 7.2:1, resulting in a rather healthy 125 hp and 218 lb-ft of torque.

End of the Line

However, by the early 1950s, the flathead’s days (in North America at least) were numbered. “It was a very good engine and had paved the way for performance in low priced vehicles,” notes Roy, “but in 1949 GM introduced the first overhead valve, short stroke V-8s, which were light and powerful. On paper, they appeared everything the flathead wasn’t – even though reality was a little different, at least at first.” However, it didn’t matter. The flathead was perceived as old technology – a throwback to the austere 1930s – and in the brave, rocket ship world that was taking shape, Ford’s veteran L-head V-8 had no place.

“When you think about it, this was quite a shame that it was dumped after ’53. It was still a viable engine,” says Richard Willim, “and guys were really starting to discover its performance potential, but as a passenger car engine it was done.” Nevertheless, a whole new chapter opened up as hot rodders embraced cheap, surplus flatheads for powering their homebuilt speed specials.

Hopping It Up

The flathead’s abundance and interchangeability turned out to be a blessing for many backyard mechanics and aspiring rodders. “The very aspect that enabled it to become the first mass-produced engine meant it was perfect for installing in one-off customized and souped-up cars at a reasonable cost,” says Willim. “There were a lot of significant changes during the flathead’s production run, but there were many parts that could be swapped between earlier and later models, particularly from 1935 onwards with the advent of the shell bearings.”

Parts included intake manifolds, distributors, water pumps, even crankshafts and rods. “One of the most popular modifications in the 1950s was using the longer stroke 4-inch Mercury crank from the 255 and putting it in a standard 239ci flathead. Some guys went even larger with 4.125-inch cranks, to get as much torque out of it as they could,” remarks Willim. But for hot rodders, there were (and still are) a few fundamental problems with the design of the Ford L-Head V-8. One of them is crank durability. “Because Ford only used three main bearings on the crankshaft,” says Willim, “it’s a weak link when you’re trying to make power. If you go beyond 8.0:1 compression and as little as 160 hp on the small [136ci] flathead, you can experience crank walk. I know guys that have put these engines in Hydroplanes and had the cranks let go. To really get some serious power [220 hp or more] you need to reinforce the bottom end with a heavy-duty bearing cap system and a girdle, otherwise it will walk on you, every time.”

Another issue is breathing. “You have to understand that when the flathead was originally designed, it was done primarily for packaging, marketing and ease of production,” remarks Willim. “As a result, air flow was poor (particularly on the intake side), because of the shape and location of the valves and also the routing. Because it also had low compression, many guys (especially after the war, when higher octane gas became more widely available) tried to raise it to boost power.

“The problem was that the stock heads and ignition system weren’t up to handling it. On the V8-60 (the small 136ci version), the coil couldn’t get hot enough to fire the mixture on an 8.0:1 compression, so you needed to go to a Vertex Magneto with a higher voltage. Today, thanks to aftermarket support from companies like Mallory and MSD, spark isn’t a problem.” Another thing was compression versus flow, something Willim has become familiar with, building many flatheads over the years, particularly V-8 60s. “By putting a high compression head on a stock block, you just kill the flow. You need 5/8-inch of transfer from the deck of the block to the highest point of the dome in the head, so on a flathead, a stock head often flows best, but you can’t get any compression out if it. When guys like [Harland] Sharp and [Zora] Arkus-Duntov were working on flow techniques, they discovered that you reach a cross point between compression and flow – if you milled the heads to boost compression, air flow would suffer. Heat was also a big problem.”

One of Duntov’s solutions was to engineer an overhead valve conversion. “A lot of people think that the Ardun heads were done purely for performance,” explains Willim, “but that wasn’t the case. It was done primarily to reduce the risk of the engines overheating, especially in heavier vehicles like commercial trucks. Ardun heads were originally designed for the European market, but hot rodders discovered that the OHV design not only reduced heat, but improved airflow, increasing power. 

More recently, Mark Kirby at Motor City Flatheads in Detroit found that playing with air routing on stock heads could reap big rewards. “The trouble with the flathead is that intake and exhaust flow is different because of the angle of the valves. The top of the bore is also square, which impedes flow,” says Willim. “By radiusing the top of the bore by the transfer area using epoxy, you create a smoother routing for the air, which increases the volumetric efficiency and helps improve power, so that’s what Kirby did. Some guys also tried smoothing the ports, but from my experience working on these engines, it’s best to leave them rough, as it helps keep the air/fuel mixture in suspension. On the bigger flatheads (221/239), I also like to install 1 3/8-inch intake valves to help breathing.”

Another source of confusion among flatheads concerns the camshaft. “When you swap the cam in one of these engines, it changes the valve timing by about three or four degrees, which can affect performance,” says Willim. “On the flatheads I build, I have cams ground specifically for the application – some guys will buy off-the-shelf camshafts like Iskendarian 77s, but they don’t work well for some situations, especially if you’re building an engine with an automatic transmission, as more guys are doing for hot rods these days, even traditional style builds. You need to have a camshaft that will provide the right amount of torque at the desired rpm to turn the converter in the trans. It’s a far cry from the old days [1940s and 1950s], when you’d just make do with a belly grind – flattening the lobes to get more duration.”


The author would like to extend a very big thank you to Roy Nacewicz and Richard Willim for their assistance with this article.


Useful Sources

Willim Vintage Engines

Early Ford V-8 Club

V-8 60 and the European Connection

Besides the 221/239/255 flatheads, Ford developed a larger 377 version for use in Lincolns and medium-duty trucks and also a light-duty version, the V8-60. “The 60 horsepower version was a small, 136 cubic-inch engine originally designed for use in Europe,” says Roy Nacewicz. “It was designed for smaller cars and actually went on to enjoy a long life across the pond – the rights were purchased by French car maker Simca, who used it until 1961.” Closer to home, however, Ford elected to introduce a 60hp L-Head V-8 on its North American cars, primarily as a cost saving measure for the 1938 model year. But it didn’t prove popular. “In 1938, the average Ford passenger car weighed about 3,200 lbs.,” says Richard Willim. “So when you consider that the V-8 60 made about 27 horsepower to the tires, the result was a slow car, especially compared with the 85 hp 221, so it wasn’t well received.”

Ford persisted with the V-8 60 hp through 1940 in the US, but then gave up, choosing instead to replace it with an in-line six in its restyled 1941 models. But the 60hp flathead found another calling. “It proved very suitable for use in midget dirt track cars and also small boats and hydroplanes,” says Willim. “The Ardun heads worked particularly well on the smaller flathead, as did multiple carb intakes. In fact, a lot of what we know today as hot rodding tricks on cars actually came from experience on the water, in hydroplane racers.”

Vic Edelbrock Sr. (who became synonymous with flathead hot rod parts in the 1940s and 1950s) actually gained a lot of his experience and knowledge through hydroplanes. “Back in the early 1950s,” says Willim, “Vic [Edelbrock] developed complete performance flathead engines, which he sold for $1000 a piece. He’d had Ed Iskendarian develop special cams for them – the 620 BS, with special low lobe centers to help provide extra thrust, since what you want to do with a boat primarily is to blow water out the back. It was versions of these cams that helped both midget racers and hot rodders gain that extra torque.” Another interesting aspect is fuel injection. “A lot of people don’t realize how much of an influence hydroplane racing had on hot rodding,” says Willim. “Bud Meyer and some of the original pioneers worked on a Hillborn fuel injection system for the flathead. It wasn’t that successful, because the head and block design makes it very difficult to efficiently introduce fuel into the runners,” says Willim, “but they were still able to set speed records in the water with a fuel injected flathead – one racer set a record by going 121 mph (and that was in the early 1950s).” And here’s an interesting fact – the use of the V-8 60 hp in Marine applications actually helped create the engine that supplanted it as a mainstay in hot rodding – the small-block Chevy. “[That] engine was designed specifically for use in hydroplane racing – that’s why it was sized at 265 cubic inches – to fit within the rules,” remarks Willim. “It just turned out to be good at a lot of other things as well.”

Ford introduced its new L-Head V-8 on the 1932 Model 18, shown here as a 3-window business coupe. Light, cheap and relatively fast, these cars were largely responsible for creating the hot rod movement.

The original 221ci flathead was designed and engineered in secrecy by a hand-picked team. Problems casting the block as one piece delayed production.

Introduction for the new V-8 had been originally slated for January 1932, but engines didn’t start materializing until April. As a result, 221-powered Fords, like this Deluxe convertible, were a rare sight when new.

By 1934, many of the early issues surrounding production and rough idling had been solved. The V-8, now rated at an impressive 75 horsepower, was proving quite the little workhorse and suitable for emergency vehicle use, like this Santa Monica lifeguard pickup.

Ford’s original 221 flathead lasted through 1942, but gained notable improvements throughout its life. Big changes occurred for 1936, with the elimination of Babbit crank bearings, and for 1938, when the cooling system was revised. Post-1938 engines can be identified by the 24 studs on each cylinder head, like this one. 

One of the inefficiencies on the flathead concerned the exhaust routing. Gases from the middle two cylinders were fed through a single port to the manifold on each side, which were linked by a crossover tube that then branched off into a pipe system on the right side. Flatheads were noted for their distinctive exhaust tone. 

Early Ford L-head V-8s (1932-33) used a single barrel carburetor, but in 1934, two-barrel Strombergs became available. These carburetors helped provided better throttle response and a much smoother idle. Simple, cheap and abundant, they were also embraced by early hot rodders on a large scale, who were soon experimenting with multi-carb setups on flatheads. 

One issue that plagued the flathead was a tendency to run hot, not aided by having the thermostats mounted amidships on each side of the engine. On later versions (1948 onwards), they were moved to the front to improve coolant circulation. 

This view shows the drive belt, water pump pulleys and distributor. Part of the reason the flathead became so popular with shade-tree mechanics and hot rodders was the parts’ interchangeability throughout the years, on everything from water pumps to intake manifolds, heads and even camshafts.

One of the most unique aspects of pre-1948 flatheads was the “crab”-type distributor mounted on the front of the block. Its location proved to be a bane for many a mechanic and finally, in 1948, Ford introduced a more conventional design mounted on top of the engine. 

Another interesting feature was a set of dual water pumps. Pumps were one of the most commonly swapped parts on these engines, but still, overheating remained a problem on many flathead powered cars.

The advent of removable shell bearings in the bottom end beginning in 1935 turned the flathead into the true mechanic’s friend. Still, a tag like this one was a good sign that parts had been serviced or reconditioned properly.

Factory stock flatheads were painted dark green. Compare this restored 21-stud engine to the used one with 24-stud heads shown previously.

Besides cooling, another aspect that plagued the flathead was top end breathing, not helped by small diameter intake valves on the cylinder head. Notice how both the intake and exhaust valves are of equal size, unlike most modern OHV V-8s, which sport larger intake valves for better high rpm flow and power. 

By the 1950s, the flathead had become the engine to soup up. Popular upgrades included aftermarket cylinder heads and intakes. One of the most successful peddlers of early speed parts, particularly intakes, was Vic Edelbrock Sr. 

Many flathead engine builders struggle with cylinder head flow issues. One modern method is to radius the top of the bore to smooth the flow of air into the cylinders. Combined with angling the valves, some tests have shown a gain of as much as 90 cubic feet per minute in cylinder head flow. 

Although the exhaust ports were rather restrictive, hot rodders did what they could to improve flow. By modifying the factory exhaust with dual outlets, like on this 1932 Ford hi-boy roadster, significant gains in power could be realized for relatively low cost. 

Besides passenger cars, the venerable L-head V-8 was also a staple in Ford trucks, including the legendary F-1 pickup, introduced for 1948. 

Today, it’s hard to imagine just how much of an impact the flathead had on the mechanized vehicle industry. Besides cars and trucks, it also found use in farm equipment. Shown is a restored Ford tractor engine. 

Ford developed a 136ci “Junior” flathead, primarily for use in smaller European cars. Although this 60hp engine wasn’t very popular Stateside (it was only offered from 1938-40), it proved highly suitable for use in midget sprint cars. 

Perhaps one of the most interesting uses for ol’ Henry’s original V-8 was in World War II midget submarines, even by the Axis powers. This Japanese Navy midget sub was captured by US forces – take a good look at what powered it through the water!


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