Ford Straight-6 engine

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170 Ford straight-6 in a 1962 Ford Falcon
ManufacturerFord Motor Company
Production1941 - 1996 (US)
1960 - present (AUS)
1961 - 1991 (ARG)
Block alloyCast iron
Head alloyCast iron
Fuel systemNormally aspirated
Fuel typeGasoline
Cooling systemWatercooled

Ford's first straight-6 engine was introduced in 1906 in the Model K. Production ended in 1907. Henry Ford did not like this car, which had a habit of tearing its transmission up. The next Ford six was introduced in the 1941 Ford. The company continued producing straight 6 engines until they were replaced in the mid-1990s by more compact V6 designs. However, Ford's Australian Branch manufactures these engines for their Falcon range to this day.

First Generation

The first generation Ford six cylinder engines were all of the flathead type. They were the G and H series engines of 226 cu in (3.7 L) used in cars and trucks and the M series of 254 cu in (4.2 L) used only in larger trucks.


H series engine

Introduced with the 1941 model year, the first Ford six (designated G series) displaced 226 cu in (3.7 L) and produced 90 hp (67 kW), the same as the Flathead V-8 that year. Like the V-8, it was also a flathead or L-head engine. In 1948, Ford raised the compression of the flathead six (designated H series or Rouge 226) so that it generated 95 hp (71 kW) and 180 lb·ft (244 N·m) of torque. The G and H series engines were used in the full-size Ford cars and trucks to replace the smaller 136 cu in (2.2 L) Flathead V8 that were used with the 1937 Ford. Ford discontinued production of the H series engine with the 1951 model year.


A 254 cu in (4.2 L) version of the flathead six was used from 1948-53 in F-6 series Ford trucks and school buses (designated the M series or Rouge 254). The M series engine produced 110 hp (82 kW) and 212 lb·ft (287 N·m). of torque. They were also used in industrial applications.

Second Generation

The second generation was produced from 1952 through 1964.


A completely new OHV six was offered for the 1952 F-series. It displaced 215 cu in (3.5 L) and produced 101 hp (75 kW). It was also used in the 1952 Ford full-size cars.


The 215 grew to 223 cu in (3.7 L) for the 1954 F-series. Output was now 115 hp (86 kW) (as the "Mileage Maker" in the trucks) and 120 hp (89 kW) in the 1955 Ford cars. Power was up to 137 hp (102 kW) in the 1956 trucks.


A 262 cu in (4.3 L) version was also produced. The 262 was built from 1961-64 for use in Heavy Duty Ford Trucks. This engine was also used for industrial applications.

Third Generation

Thriftpower Six
Also calledFalcon Six
Production1960 - 1984
Dry weight385 lb (175 kg)
Power output88 hp (66 kW) - 155 hp (116 kW)

The third generation was produced at the Lima Engine plant in Lima, Ohio from 1960 through 1984. Officially dubbed the Thriftpower Six, this engine line is sometimes referred to as the Falcon Six. Note: Car companies including Ford, switched from gross ratings to net horsepower and torque ratings in 1972 (mainly because of the emissions laws being enacted nationwide at the time). Changes in engine compression and emissions controls make it difficult to compare engines from various production years (especially pre-1972).


140 Thriftpower Six
Production1960 - 1964
Bore3.5 in (88.9 mm)
Stroke2.5 in (63.5 mm)
Displacement144 cu in (2.4 L)
Power output84 hp (63 kW) @ 4200 RPM
Torque output134 lb·ft (182 N·m) @ 2000 RPM
Compression ratio8.7:1

The 144 cu in (2.4 L) engine was first introduced in the 1960 Ford Falcon. The 144 was made from 1960 through 1964 and averaged 90 hp (67 kW) during the production run. While not known for being powerful or a stout engine, it proved to be economical and could get fairly good gas mileage for the time (up to 25-30mpg). This small six was the basis for all the Ford "Falcon" straight six engines. The intake manifold on this series of engine was cast integrally with the cylinder head (this design was also used by Chevrolet with their third generation inline six); as a result, they could not be easily modified for greater power. This engine had four main bearings and can be identified by the three freeze (core) plugs on the side of the block.

This engine was used on:


170 Thriftpower Six
170 Ford six in a 1966 Ford Mustang
Production1961 - 1972
Bore3.5 in (88.9 mm)
Stroke2.94 in (74.7 mm)
Displacement170 cu in (2.8 L)
Power output105 hp (78 kW) @ 4400 RPM
Torque output156 lb·ft (212 N·m) @ 2400 RPM
Compression ratio9.1:1

In 1961 the 170 cu in (2.8 L) became an option for the Falcon line. The original 1964½ Ford Mustang used a 101 hp (75 kW) version. The Econoline van and Ford Bronco received a heavier duty version with mechanical valve lifters. This engine had four main bearings and can be identified by the three freeze (core) plugs on the side of the block. The 170 was dropped from production in 1972.


The 200 cu in (3.3 L) was introduced in the middle of 1963. The 1965 Mustang used this engine as standard with 120 hp (89 kW). The Mustang continued to use the 200 as its base engine until it was dropped in 1971. The 200 was used in the Maverick, and continued on in the Fairmont until the Fairmont was retired at the end of the 1983 model year. Its re-skinned replacement, the LTD, used the engine for another year until it was replaced by the 3.8L Essex V6. The 200 engine had four main bearings at introduction through 1964 and can be identified by three freeze (core) plugs on the side of the block. All 1965 and later 200 CID engines were upgraded to seven main bearings to increase its durability. The 1965 and later engine can be identified by 5 freeze (core) plugs on the side of the block.

The 4-cylinder Ford HSC engine was based on the 200.


The 250 cu in (4.1 L) straight six was an engine option offered in 1969 in the Mustang and 1970 in medium sized Ford cars(Maverick). Output was 155 hp (115 kW) in the Mustang, and became the base engine in 1971. Power was down to 98 hp (73 kW) for 1972 and just 88 hp (66 kW) the next year. The last year of production for the 250 was 1980. This engine had seven main bearings and can be identified by the five freeze (core) plugs on the side of the block. The block uses a low mount starter and six bellhousing bolts sharing its bellhousing with the Windsor V-8s 302-351W, late (1965-68) 289, 351 Cleveland, modular V-8s (4.6-5.4), and the 240-300 CID Ford Six.


In Australia these engines (250 Crossflow) were continued as the 4.1 L (≈250 cu in) (both carb. and fuel injected). In the XF model Falcon starting from 1984 two different capacity cross flow six cylinders were available. Both being high compression engines, a 3.3 L and 4.1 L were available. The Cylinder Head is made of aluminum alloy and it is a cross flow design. The valve guides and valve seats are made of cast iron and are retained in the cylinder head by an interference fit. The Hydraulic Lifters are utilized to provide zero lash. The Alloy head was used to improve warm up time and reduce fuel consumption and emissions. The 3.3L was fitted with a Stromberg carburetor and the 4.1L was fitted with a Webber carburetor which had improved consumption over the Stromberg. The Fuel Injected version had six individual injectors placed just in front of the inlet valve, and was only available as a 4.1 L. There were changes to the carburetor based engine to accommodate the Electronic Fuel Injection system. The compression ratio on the 4.1 L was 8.89:1. The cylinder head intake ports had been modified to provide clearance for the injectors and a new intake manifold was designed and a host of other changes was made in the engine bay to accommodate the new fuel system.

  • Power at Specified RPM (DIN) Pre '86 running on Leaded Fuel
    • 3.3 L 90 kW (121 hp) @ 4100 rpm
    • 4.1 L Carburetor 103 kW (138 hp) @ 3750 rpm
    • 4.1 L E.F.I Engine 120 kW (161 hp) @ 4000 rpm
  • Torque at Specified RPM (DIN) Pre '86 running on Leaded Fuel
    • 3.3 L 240 N·m (180 lb·ft) @ 2500 rpm
    • 4.1 L Carburetor 316 N·m (233 lb·ft) @ 2400 rpm
    • 4.1 L E.F.I Engine 333 N·m (246 lb·ft) @ 3000 rpm
  • Power at Specified RPM (DIN) ADR 37 compliant engine running on Unleaded
    • 3.3 L 89 kW (119 hp) @ 4000 rpm
    • 4.1 L Carburetor 99 kW (133 hp) @ 3600 rpm
    • 4.1 L E.F.I Engine 123 kW (165 hp) @ 4000 rpm
  • Torque at Specified RPM (DIN) ADR 37 compliant engine running on Unleaded
    • 3.3 L 238 N·m (176 lb·ft) @ 2200 rpm
    • 4.1 L Carburetor 303 N·m (223 lb·ft) @ 2000 rpm
    • 4.1 L E.F.I Engine 328 N·m (242 lb·ft) @ 3000 rpm

In 1988 when the EA Falcon was released two capacities were available, 3.2 L and 3.9 L. Using the cross flow design the inline 6 cylinder was of a single overhead cam-shaft design. The valve seats and valve guides are cast iron and retained in the alloy head by interference fit. The camshaft and auxiliary shaft are driven by a 'Duplex' chain. The duplex chain drives the distributor and the oil pump shafts. The camshaft is supported on the cylinder head by using 'topless' bearings. Bearing liners are not used. The shaft is held in position using valve spring pressure. Hydraulic lash adjusters mounted on the rocker arms are utlized to provide zero valve lash. As with all previous and current models the block is cast iron. 4.0 L (≈244 cu in) (fuel injected), and a 3.9 L (≈238 cu in) (fuel injected), and are, in its 4.0 L (≈244 cu in) form, still used in base model Ford Falcons to this day (and some higher models such as the BA Falcon XR6 and XR6 Turbo.). This engine used a SOHC cylinder head in the EA-AU models (from 1988, all 3.9s and pre-BA 4.0s), and switched to a 24-valve DOHC renamed "Barra" in the BA model in 2002. Production was scheduled to end in 2010 when Falcons and Territorys were to switch to imported Duratec V6s, but that decision was reversed on the 20th of November 2008.

In the EF model Falcon the standard engine employed a high-energy coil-pack ignition system. However, the EL falcon used a distributor/coil ignition setup, as in Falcon models prior to EF.

Falcon model Capacity Induction Valvetrain Fuel Power Torque Notes
XY, XA, XB 4.1 L Carburettor OHV Leaded 116 kW (156 hp) 325 N·m (240 lb·ft)
XC 4.1 L Carburettor OHV Leaded 92 kW (123 hp) 289 N·m (213 lb·ft) Crossflow cylinder head
XD 4.1 L Carburettor OHV Leaded 94 kW (126 hp) 305 N·m (225 lb·ft)
XE 4.1 L EFI OHV Leaded 111 kW (149 hp) 325 N·m (240 lb·ft) Bosch LE II Jetronic fuel injection
XF 4.1 L EFI OHV Unleaded 121 kW (162 hp) 325 N·m (240 lb·ft) EEC-IV Multi-point injection
EA, EB 3.9 L EFI SOHC Unleaded 120 kW (161 hp) 311 N·m (229 lb·ft)
EA, EB 3.9 L EFI SOHC Unleaded 139 kW (186 hp) 338 N·m (249 lb·ft) EEC-IV Multi-point injection
EB series II, ED 4.0 L EFI SOHC Unleaded 148 kW (198 hp) 348 N·m (257 lb·ft)
XR6 ED, EF, EL 4.0 L EFI SOHC Unleaded 164 kW (220 hp) 366 N·m (270 lb·ft)
EF, EL, AU 4.0 L EFI SOHC Unleaded 157 kW (211 hp) 357 N·m (263 lb·ft) Coil-pack ignition system (EF and AU Only)
AU series II & III 4.0 L EFI SOHC LPG 143 kW (192 hp) 362 N·m (267 lb·ft) Dedicated LPG
XR6 AU 4.0 L EFI SOHC Unleaded 172 kW (231 hp) 374 N·m (276 lb·ft) VCT Variable Valve Timing
BA 4.0 L EFI DOHC Unleaded 182 kW (244 hp) 380 N·m (280 lb·ft)
BA XR6 Turbo 4.0 L EFI DOHC Unleaded 240 kW (322 hp) 450 N·m (332 lb·ft) Garrett GT40 turbocharger
BF 4.0 L EFI DOHC Unleaded 190 kW (255 hp) 383 N·m (282 lb·ft)
BF XR6 Turbo 4.0 L EFI DOHC Unleaded 245 kW (329 hp) 480 N·m (354 lb·ft) Garrett GT3540 turbocharger
FG 4.0 L EFI DOHC Unleaded 195 kW (261 hp) 391 N·m (288 lb·ft)
FG XR6 Turbo 4.0 L EFI DOHC Unleaded 270 kW (362 hp) 533 N·m (393 lb·ft)

Fourth generation

Truck Six
Production1964 - 1996
Stroke3.18" (240)
3.98" (300)
Displacement240 cu in (3.9 L)
300 cu in (4.9 L)
Fuel systemNormally aspirated
Fuel injection
Power output120 hp (89 kW) - 170 hp (127 kW)
Torque output260 lb·ft (353 N·m)

Produced at the Cleveland Engine plant in Brook Park, Ohio from 1964 through 1996, the 240 and 300 Sixes are well-known for their durability. Simple design and rugged construction continue to endear these engines to a number of Ford enthusiasts to this day.

One example of the engine's sturdy design is the fact that no timing chain or timing belt (both of which can break, causing unwanted downtime or even engine damage) is used. This generation of Ford Six was designed with long-wearing gears for that purpose instead. Few, if any, modern engines use timing gears; belts are by far more common, especially among non-domestic automakers.


The 240 cu in (3.9 L) six for 1963 - 1970 full sized cars (continued to 74 in fleet models) and 63-77 trucks produced 150 hp (112 kW). In stationary service (generators and pumps) fueled by LPG or natural gas, this is known as the CSG-639.


A big 300 cu in (4.9 L) six was added for the F-series in 1965 and was essentially a 240 cu in (3.9 L) with a longer stroke (the two are nearly interchangeable aside from a few parts). It produced 170 hp (127 kW). The 300 became the base F-series engine in 1978 at 114 hp (85 kW) (hp number changes due to Ford switching to Net power ratings in 1971). Power outputs were increased to roughly 122 hp (91 kW) during the early 1980s before fuel injection was introduced. This became the primary engine of the line, eclipsing the 240. Unlike the Falcon engine, it featured separate intake and exhaust manifolds which could be easily replaced with aftermarket manifolds offering the promise of even more power, through the installation of larger carburetors and a higher flowing exhaust system.

Also during the late sixties and early seventies, the 300 was used in larger vehicles such as dump trucks, many weighing into the 15,000–20,000 pound (7,000–9,000 kg) range. These 300s were equipped with a higher flow HD (Heavy Duty) exhaust manifold since the engines were going to be constantly working in the 3000–4000 rpm range. These rare, yet effective, manifolds had higher flow than the electronic fuel injection 4.9 (300) manifolds and some headers.

This engine is also used by Stewart and Stevenson in the MA Baggage Tow Tractor (pdf), as well as a multitude of other pieces of equipment, such as ski lifts, power generators, wood chippers, tractors, and, until they converted to diesel engines, most UPS trucks. Many UPS trucks still use the 300 to this day.

In stationary service (generators and pumps) fueled with LPG or natural gas, this engine is known as the CSG-649.


Engine sizes were converted to metric for 1983, causing the 300 to become the "4.9". Fuel injection and other changes in 1987 pushed output up to 150 hp (112 kW). This engine was gradually phased out, ending production in 1996 and replaced by the Essex V6 in the F-series trucks with their 1997 redesign. However, it was renowned for its durability, low end torque, and ease of service. Often going for more than 300,000 mi (480,000 km) before rebuilds, many continue in service. Ford also built some trucks with the 300 cubic inch (4.9 L) engine coupled with the Ford C6 transmission and the Ford E4OD transmission as well as the Mazda built M5OD 5 speed manual transmission through the mid-1990s. This combination is a durable truck powertrain. The 4.9 liter 6 cylinder was built in Cleveland, Ohio.

See also

External links