7.3L International IDI Diesel

7.3L IDI Diesel Specs, History, & Information

For the 1988 model year, International altogether retired the 6.9L IDI and in its place began producing the 7.3L IDI. The 7.3 was based on the 6.9's architecture, but underwent many changes in order to meet emissions requirements and the growing demand for performance. The 7.3 IDI was only offered naturally aspirated until the 1993 model year, where a turbocharged version became optional. The 7.3L IDI was far from winning any races, but its high compression ratio gave it "snappy" throttle response and it had enough torque to meet the towing needs of F-Series pickup owners. In time, International and Ford would learn that the 7.3L IDI was susceptible to cavitation in the cylinder walls - a problem that the 6.9L does not often experience, as its walls are slightly thicker than the 7.3's.

Naturally aspirated versions of the engine were rated at 185 horsepower while the later turbocharged engines were rated at 190 horsepower. While opting for the turbocharger only resulted in an extra 5 peak horsepower, it more importantly added an additional 50 lb-ft of torque. The 7.3L IDI is generally classified as a medium duty engine as it was used in applications that far exceeded Ford's pickup truck ratings. It was backed by either the ZF 5 speed manual or C6 3 speed automatic transmission until 1989, when the 4 speed E4OD replaced the C6 as the available automatic transmission. The overdrive transmissions greatly improved fuel economy for the completely mechanical 7.3L. Unbeknownst at the time, the 7.3L IDI would become an iconic engine in the history of diesels, building Ford/International's reputation of longevity and reliability, as well as paving the way for International's ultimate creation; the 7.3L Power Stroke.

7.3L IDI Diesel Specs


International Navistar

Production Years:



Ford F250, F350, F-Super Duty


90 degree V-8

Firing Order:

1-2-7-3-4-5-6-8 (stamped on intake manifold)

Dynamic Timing:

8° BTDC +/- 2°


• Cast iron engine block
• Cast iron cylinder heads with 1/2" head bolts


444 cubic inches, 7.3 liters




4.11 inches


4.18 inches


Indirect injection (IDI), Stanadyne DB-2 injection pump


• Naturally aspirated 1988 - 1992 model years
• Turbocharged or naturally aspirated 1993 - 1994 model years, Garrett T3 internally wastegated turbocharger (.82 AR), non-intercooled


900 lbs. dry (approx)

Oil Capacity:

10 quarts w/ filter

Peak Horsepower:

• 185 hp @ 3,000 rpm (naturally aspirated)
• 190 hp @ 3,000 rpm (turbocharged)

Peak Torque:

• 338 lb-ft @ 1,400 rpm (naturally aspirated, 1988 - 1992 MY) years)
• 358 lb-ft @ 1,400 rpm (naturally aspirated, 1992.5+ MY)
• 388 lb-ft @ 1,400 rpm ( turbocharged)


Documentation from Ford Motor Company states that the turbocharged version of the 7.3L IDI was introduced primarily to combat power loss experienced at high altitudes. Like the 6.9L IDI, the 7.3L held strong in the market, though Chrysler's Cummins powered Dodge Ram proved to be a worthy competitor when it became available for the 1989 model year. Ford's advantage was the reputation they had built with the 6.9L and were continuing with the 7.3L IDI. The 7.3L IDI would be replaced by the 7.3L Power Stroke midway into the 1994 model year. The 7.3L Power Stroke shares displacement with the 7.3L IDI, but that is where the similarities end. The Power Stroke was a completely different engine, and not to be confused with the IDI. It was an electronically controlled, turbocharged, direct injection diesel with a hydraulic (HEUI) injection system. Properly maintained, the 7.3L IDI is well known for its longevity.

7.3L IDI Naturally Aspirated vs Turbocharged

To combat higher cylinder pressures and temperatures, several changes were made to the turbocharged version of the 7.3L IDI.

• Cylinder head gasket received a larger/heavier fire ring.
• Piston wrist pin bore was increased from 1.1108" to 1.3086", and the wrist pin was increased to match.
• New piston design that featured an anodized head and updated piston ring design.
• Updated exhaust valve manufactured from a higher strength alloy.
• Oil cooler increased from 24 fins per inch to 30 fins per inch.
• Heavier duty flywheel and engine damper (not interchangeable with the naturally aspirated version).
• Separate injection pump calibration and G code injector nozzles (naturally aspirated engines had E code injector nozzles).

Additionally, turbocharged engines had the glow plug controller relocated to the passenger side valve cover and the CDR moved to the driver side valve cover (on naturally aspirated engines, both are located at the rear of the intake manifold).

6.9L IDI vs 7.3L IDI

Though the 7.3L IDI was ultimately a derivation of its predecessor, many design changes reduced the interchangeability of their respective components.

• The 7.3L IDI has a different cylinder head design that includes a larger prechamber and offset glow plugs.
• Where as the 6.9 IDI has 7/16" cylinder head bolts, the 7.3 IDI received larger 1/2" head bolts.
• Different intake valve materials.
• Bore increased from 4.00" to 4.11".

7.3L IDI diesel horsepower and torque graphs (curves)
7.3L IDI and 7.3L IDI Turbo Horsepower/Torque Curves