Classic Inlines
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Legendary Ford - Magazine Article

Published in Legendary Ford's July/August 2008 issue.

History of the Ford Inline Six

The inline six by design will produce more torque pound for pound than a V8. The reason is simple; a V8 spins the crankshaft 90 degrees for each stroke, while the inline six turns the crank 120 degrees between strokes. This means for every revolution, the inline design inherently has more time to deliver power to the crankshaft. Typically, maximum torque is produced between 2500-4000rpm, where it happens to be needed most on a street driven vehicle. However due to the harmonics of the inline design, the average six should not be spun above the 5000-6000prm range on a regular basis, unless the engine has been properly balanced and a performance damper is utilized. This is especially true in race applications, where higher rpm ranges are frequently seen.

The first inline six was produced by Ford in 1906, however it was only in production for less than a year as it had a terrible reputation for tearing up transmissions. Hence the inline design was abandon for many years, until transmission technology could catch up and handle the massive torque produced by an inline design. 

The first generation of inline sixes was introduced in 1941 and utilized a flathead design. The 226ci, known as the Rogue 226 or H Series, was used in full sized cars and light trucks until 1951. While the 254ci, known as the Rogue 254 or M Series, was used in F Series trucks, school buses, and industrial applications from 1948 through 1953 producing 110HP.

226ci Flathead Rogue Six

The second generation of inline sixes was designed with over-head valves, and offered in three sizes. The 215ci, producing 101hp, was introduced in 1952 and used in F Series trucks and full sized cars until 1953. In 1954 the 215ci grew to 223ci of displacement, and saw continued use in F Series trucks and full sized cars through 1956. Known as the Mileage Maker, it produced 137HP in its final version.  A larger six with 262 cubic inches of displacement was also offered, but was only available in Heavy Duty Ford Trucks and industrial applications.

The third generation, officially named the Thrift Power Six, is more commonly known as the Falcon Six.  Offered in 144/170/200/250ci displacements, as well as 221ci in Australia, Argentina, and Brazil, it is often referred to as the small block six. The small six was used in several Fords models including the Bronco, Econoline, Fairlane, Fairmont, Falcon, Galaxie, Granada, Maverick, Mustang, Ranchero, Torino, and their Mercury counterparts such as the Comet, Meteor, Monarch, Montego, and Zephyr. The first variation, at 144ci of displacement, was introduced in the 1960 Falcon. With a 3.50” bore and a 2.50” stroke, it was low on power and very slow to accelerate. Before the year was out, the displacement was raised to 170ci by increasing the stroke to 2.94 inches. When Ford introduced the Mustang in April 1964, the 170ci six was standard equipment, with 105HP at 4,400 rpm.

Stock Falcon Six

Early in 64, the bore and stroke were again increased, to 3.68 and 3.126 respectively, which resulted in 200ci of displacement. Only available in the Fairlane, the 200ci six maintained four main bearings, like the earlier 144ci and 170ci blocks. However in mid production 1964, the blocks were recast to incorporate seven mains. This change was made to minimize the harmonics of the long crankshaft, thus increasing the durability. This resulted in one of the strongest bottom ends ever produced, and is often described as ”indestructible”. At this time Ford also incorporated hydraulic lifters, rather than solid lifters as used in the earlier sixes. In August 1964 the 200ci was offered as standard equipment in the Mustang with 120HP at 4,400 rpm, and 190 lb-ft. of torque.  The seven main blocks can be easily identified with five freeze plugs along the passenger side of the block, whereas the earlier four main blocks only have three freeze plugs.

Falcon Six - with air and power steering.

In 1968 Ford Australia raised the deck height and increased the stroke to 3.46” which yield 221ci of displacement, and increased the output to 135HP. However these engines were only offered for two years, and only in Australia and Argentina. In 69 (70 in AU and AR) the deck height was raised 1.66 inches and the stroke lengthened to 3.91, resulting in a 250ci engine. What this meant for the little six was big-six torque, with 240 lb-ft of twist at 1,600 rpm. The 250ci six was an option for 69-70 Mustangs, but was offered as standard equipment in the 1971-1973 Mustangs. The 250ci blocks are easily identified by a four bolt water pump, verses a three bolt water pump on the 144/170/200/221ci sixes.

Australian Inline Sixes
Americans were spoiled in the 60's; the economy was good and gas prices low. Ford USA introduced the small block V8, which instantly became the choice of consumers due to the substantial increase in performance. Consequently Ford USA halted the research and development of the small six, however this is not the case in countries overseas. Ford’s Australian and Argentine Branches continued to develop the small six, as they remained extremely popular. In the fall of 1970, Ford Australia did away with the integral log cylinder head and introduced the 250-2V cylinder head.  The new cast iron cylinder head utilized a removable cast alloy intake and a Stromberg two-barrel carburetor; verses the anemic 1V carburetor used on all previous log style cylinder heads. Headers were also offered as stock equipment, which raised the horsepower output to 145HP.

Australian 250-2V

Production of the 250-2V is terminated in 1976, and the 250ci block redesigned to incorporate a new cast iron cross-flow cylinder head. The new XF head loosely resembled a Cleveland cylinder head with canted valves, and increased the small six’s output to 152 horsepower.  In 1978 the 250-XF (cross-flow) gets a cast aluminum head, which was fifty-one pounds lighter, and horsepower is raised to 155HP. Electronic Fuel Injection is offered as an option in 1980 and increases performance to 168HP with 240lbs of torque. 1988 saw the introduction of an overhead cam design, as well as a reduction in displacement to 238ci and 244ci. Today's modern Aussie sixes are a far cry from the classic US versions, with cross-flow cylinder heads, alloy intakes, dual overhead cams, variable cam timing, fuel injection, and turbo chargers, they produce up to 329HP with 354 lbs of torque.  While Ford Australia continues to manufacture an inline six for their Falcon and Ute models, production is scheduled to end in 2010 in favor of the Duratec V6.

Australian Ford Intech

The forth generation saw the introduction of two big block sixes, the 240ci and the 300ci, which were used in full sized cars and F-series trucks, as well as Heavy Duty Trucks from 1964 through 1996. Both the 240ci and the 300ci had seven main saddles and used timing gears rather than a chain or belt. Unlike the small sixes, the big six utilized a removable intake manifold and was offered with fuel injection, and a high flow heavy duty exhaust manifold (300ci only).  The 300ci also saw duty in baggage handlers, ski lifts, power generators, wood chippers, tractors, and fleet operations such as UPS. 

Australian Turbo-charged Ford Intech

In Summary
While the small inline sixes of the 60’s, 70’s and 80’s offered meager performance, they were often preferred for their reliability, excellent mileage (25-30mpg), ease of maintenance, availability, and affordability.  More often than not, the six-cylinder engine was the only choice available, as models with the V8 option usually sold as fast as they rolled onto the showroom floor.  This is even true today, as V8 powered Mustangs and Falcons are becoming increasingly difficult to locate, while their inline six brethren seem to be more plentiful, and normally sell for less. Considering most enthusiast still think of the small six as “Grandma Grocery Getter”, it’s easy to understand why V8 swaps have been so popular over the past decade. However that trend is coming to an end as more Ford enthusiast are realizing the full potential of the inline six, and an increasing number of performance products are popping up on the aftermarket scene.  While most will agree that the sixes are economical, many enthusiasts are unaware of the power potential waiting to be unleashed. In another tech article, we will take a look at the various modifications and the newest products being offered for the small six.

Written By: AzCoupe

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