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  • Ford Diesel Truck - Ford's First Diesels

Ford Diesel Truck - Ford's First Diesels

How The International-Powered Fords Came To Be

Mike McGlothlin
Oct 1, 2008
Photographers: Courtesy Of Oldoilers.Net
Photo 2/13   |   ford Diesel Truck 1983 Ford F250
Simplicity is something most of us seek out in life, but we often take for granted how complicated the new vehicles we drive to work really are. However, there was a time when the complex, electronically controlled trucks we drive today didn't exist. In 1978, International Harvester-a leader in the commercial trucking industry-began developing a diesel engine that would power another industry leader's light-duty pickups, Ford Motor Company's 3/4-ton and 1-ton trucks. In the early 1980s, full production of the 420ci 6.9L engine began at International's Indianapolis plant for the purpose of not only powering Ford trucks and vans, but International's bus fleets as well. This correlated relationship sparked what is now a 25-year success story in which International-powered Ford trucks still consistently outsell the competition.
Photo 3/13   |   In its first year of existence, the 6.9L put out 170 hp at 3,300 rpm and 315 lb-ft at 1,400 rpm. Torque peaked at 338 lb-ft the following year due to a compression ratio increase.
Why A V-8?It has always been a mystery as to why International chose to build a V-8 diesel application for light-duty Ford pickups at a time when nearly its entire agricultural and trucking lineup consisted of inline-six designs. As it turns out, several different factors weighed heavily on the minds of International's engineers. First and foremost, both companies knew a diesel-powered pickup would sell, but they wanted to offer consumers an engine that would pull effectively and operate across a broader rpm range than a traditional inline design. Their predominant goal behind building a V-8 was to provide a diesel engine that built torque low and horsepower up high to give drivers a wider powerband than an inline-six would give. Ford and International wanted consumers to be able to have both speed and towing as options. In addition, engineers believed a V-8 would allow them to meet the new emissions standards expected in the 1980s. Prior to production, the 6.9L was subjected to more than 52,000 hours of testing, and the result was a bulletproof design that proved more powerful than GM's 6.2L diesel offered in K-series pickups.
Indirect-InjectionUnlike the direct-injection diesels, Ford's first diesels were indirect-injection engines. In this process, combustion actually begins in a prechamber between atomized fuel and compression-heated air, which then spreads into the combustion chamber. The final decision was made to utilize a Harry-Ricardo-based indirect-injection combustion system. Coined the "Comet" design, the proven induction swirl chamber in the engine's cylinders allowed for controlled, efficient, and manageable airflow. This type of design was considered very modern in its day.
Photo 4/13   |   The 6.9L engine's dry weight was 860 pounds. In comparison, the 460ci gas engine option weighed 720 pounds.
6.9L/7.3L BasicsSimple in design, the 6.9L and 7.3L were non-turbo, naturally aspirated engines and used cast-iron blocks and heads, a Stanadyne DB-rotary mechanical fuel pump located in the front of the engine valley, and Stanadyne pintle-nozzle injectors. In 1983 the 6.9L put out 170 hp at 3,300 rpm and 315 lb-ft at a low 1,400 rpm. By mid-1983, Ford trucks equipped with the 6.9L were selling rapidly, which in turn led Ford to ask International to increase production. International agreed to the increase, which was projected to result in $100 million of extra revenue. In 1984, the 6.9L engine's compression was increased from 20.7:1 to 21.5:1, raising torque to 338 lb-ft at the same low 1,400 rpm. Horsepower did not increase. Both 1986 and 1987 proved to be years of change. In 1986, following a prior decision to sell off its agricultural division, IHC's commercial truck lines continued under the Navistar International nameplate. The following year became the interval year in which the 6.9L became the 7.3L. In an effort to increase power, Navistar increased the 6.9L's bore from 4.00 inches to 4.11, resulting in the 444ci 7.3L. Other than subtle differences, such as bigger diameter piston pins and larger head bolts, the 7.3L was virtually the same as the 6.9L. From 1988 to 1992, 7.3L engines made roughly 180 hp at 3,300 rpm and 345 lb-ft at 1,400 rpm.
Photo 5/13   |   The 7.3L turbo IDIs were conservatively rated for 190 hp at 3,300 rpm and 388 lb-ft at 1,400 rpm.
The Arrival Of The Turbo IDIIn 1993, Ford pickups came with two diesel engine options. For the first time, and in keeping up with Dodge's already turbocharged 5.9L and GM's 6.5L, a factory turbocharger was offered on Ford IDI trucks. While the naturally aspirated version was still available, the turbo option easily proved to be the better seller and netted the 7.3L 190 hp at 3,300 rpm and 388 lb-ft at 1,400 rpm.
Performance Upgrades That WorkAlthough the factory Ford IDIs were non-turbocharged and underpowered in their first decade of existence, the aftermarket was very busy developing ways to bring these beasts to life. One pioneer in the aftermarket industry was Max Lagod of Hypermax, who had a bolt-on turbo system designed and ready to go at virtually the same time the '83 Fords made it to dealer lots. According to Lagod, it is not uncommon for a 6.9L or 7.3L outfitted with a turbo, intercooler, freer flowing exhaust, and a little fuel pump work to make 325 flywheel hp. Companies like Banks and ATS also offer turbo and intercooler systems.
Photo 6/13   |   Due to an increase in compression ratio from 20.7:1 to 21.5:1, this '84 F-250 came equipped with the improved 6.9L rated for 338 lb-ft.
Performance Upgrades That Don't WorkNever known for having as much factory potential as the 5.9L Cummins during this era, an aftermarket turbo was the best way to gain any respectable amount of power. Tinkering or turning up an IDI Ford's fuel pump won't net you any noticeable gains. Cutting out the "soup bowl" on the bottom of the air intake cover won't make much of a difference, so anyone wanting to really see what an old IDI is capable of will simply have to pay to play.
A Proven DesignWhile not nearly as state-of-the-art as the newer Power Stroke engines, these early diesels put out respectable power considering their naturally aspirated design. Like GM (and partially because of their 5.7L), at the time of their arrival, these IDIs faced an uphill battle against a public that was convinced diesels were unreliable. The first Ford diesels not only proved that assumption wrong, but were so reliable that virtually the same basic design and technology underwent no changes in its 12-year production run.
Photo 7/13   |   A mechanical rotary-style fuel pump from Stanadyne (model DB2) came on all IDI engines and allowed injection pressures up to 6,700 psi.
Think idi can't make big horsepower?Back in the early 1990s, max Lagod of Hypermax put together an extraordinary engine package for a customer yearning to compete in sled pulling. With nothing holding him back, Lagod designed a 7.3L that included two Garrett turbos (which were state-of-the-art then but probably not manufactured anymore), a Bosch inline P-pump, custom injectors, a fabricated intake and exhaust manifolds, and slight cylinder head work.
Surprisingly, much of the factory engine components were retained, such as the crankshaft, block, and pistons-although the connecting rods were heat-treated. Compression on the engine was 15:1, which called for ether-assisted startups. Soon after entering this wild IDI into area-sanctioned sled pulling events, the engine was banned. Not to be discouraged, the owner turned to drag racing. Rumor has it that the truck graced with this 7.3L beast put out 1,200 hp and ran quarter-mile times in the 9-second range!
All of that power came with a price though, as the engine was infamous for its unreliability. Apparently, the engine block flexed so much on several occasions that the rear of the engine block broke off and required the utilization of rubber freeze plugs!
Year: 1983
HP: 170 hp at 3,300 rpm
Torque: 315 lb-ft at 1,400 rpm
Transmission(S): C6 (three-speed) T-19 BorgWarner (four-speed)
Engine Notes: 6.9L 420ci, naturally aspirated 20.7:1 compression
Year: 1984-1987
HP: 170 hp at 3,300 rpm
Torque: 338 lb-ft at 1,400 rpm
Transmission(S): C6/T-19
Engine Notes: 6.9L compression increased to 21.5:1
Year: 1988-1992
HP: 180 hp at 3,300 rpm
Torque: 345 lb-ft at 1,400 rpm
Transmission(S): C6 & T-19 ('88)E4OD & ZF five-speed ('89-'92)
Engine Notes: 7.3L 444 ci, naturally aspirated Increased 6.9L bore from 4.00 to 4.11
Year: 1993-1994
HP: 185 hp at 3,300 rpm190 hp at 3,300 turbo
Torque: 360 lb-ft at 1,400 rpm, 388 lb-ft at 1,400 turbo
Transmission(S): E4OD/ZF five-speed
Engine Notes: Two options: 7.3L naturally aspirated or 7.3L turbo


Warrenville, IL 60555



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