Ford 6.9 IDI Specifications
The 6.9L IDI is a naturally-aspirated all-mechanical diesel engine. IDI stands for its ‘indirect injection’ fuel system, which features a mechanical rotary injection pump and mechanical injectors. Original engines never came with a turbo, but many owners added aftermarket Banks turbochargers to increase power.
ENGINEFORD 6.9L IDIMANUFACTURERFORDYEARS PRODUCED1983 to 1987DISPLACEMENT420CI (6.9L)CONFIGURATIONV8FUEL TYPEDIESELCOMPRESSION RATIO20.7:1 (1983) 21.5:1 (1984 to 1987)BORE4 INCHESSTROKE4.18 INCHESHORSEPOWER270 hp (3,300 RPM)TORQUE338 lb-ft (1,800 RPM)FUEL ECONOMY10-19 MPG (EST)
The 6.9-liter IDI has a displacement of 420 cubic inches. In 1983, the engine had a compression ratio of 20.7:1, which was increased to 21.5:1 for model year 1984 and onward. The 6.9L IDI produced up to 170 horsepower at 3,300 rpm and 338 lb-ft of torque at 1,400 RPM.
Ford 6.9 IDI Reliability
Is the 6.9L IDI a good engine? Most people would say that it is. International IDI engines (in general) have a long-standing reputation for durability thanks to their mechanically robust and overbuilt design.
Other than occasional issues with head gaskets and glow plugs, there aren’t many generational issues or defects with the 6.9L IDI. However, some IDI engines suffer from overheating issues, so a well-serviced cooling system is particularly important.
6.9L IDI Diesel Performance
One downside of the 6.9L IDI is its apparent lack of power. Owners of modern computer-controlled diesels or large-displacement gasoline engines will likely be disappointed with the slow acceleration of the 6.9L IDI.
The easiest way to increase an old 6.9L diesel’s power output is to turn up the injection pump, but this is a risky solution. Cranking up the pump can cause the engine to roll coal as well, though fuel economy will suffer. Another common modification is a Banks turbo kit, which has been popular for years. Adding a turbo is the most potent bolt-on modification in common use.
About THE AUTHOR
I rebuild & restore classic cars and trucks when I'm not researching and writing about all things automotive. My current project is a 1978 Ford.Read more about Joshua Weinstein