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Ford 6.9L IDI Diesel Specs

Guide to International’s 6.9L IDI Diesel Engine

In 1982, Ford did something revolutionary for the consumer truck market. They partnered with International Harvester to introduce the 6.9L IDI diesel engine in their heavy duty truck lineup. The 6.9L IDI diesel engine became an available option on 1983 model year trucks. It offered comparable horsepower numbers to Ford’s 6.6L V8 gasoline engine at the time, but had 6% more torque. Owners opting for the new 6.9l IDI engine also reaped the benefits of a diesel engine, including heavier duty components for better durability and significantly better fuel economy. In this article, we’re going to give you all the Ford 6.9L IDI Diesel specs you can handle. We’ll cover the 6.9L IDI’s fuel injection system, aspiration system, and even towing specifications.

International Harvester 6.9L IDI Diesel Specifications
1986 Ford F-350 with the International 6.9L Indirect Injection Diesel Engine. Photo sent in by @ch_trucks on Instagram, the owner of @Chmobileautodetail in Texas.

Key Features of the 6.9L International Harvester Diesel Engine

The 6.9L IDI diesel engine made by International Harvester is significantly different than the modern diesel engines of today. This engine is mechanical, uses indirect injection and it’s also naturally aspirated. While this might seem simplistic and inefficient to us now, the 6.9L IDI V8 diesel engine was very impressive in its time period. Its simple design also contributes to its reliability. Many IDIs are still on the road today because of just how reliable and durable they can be. We’re even re-building our own 6.9L IDI as we’re writing this post!

Ford 6.9L IDI Diesel Specs
International Navistar (International Harvester) 6.9L Non-Turbocharged IDI diesel engine. Photo taken from a 1984 Ford F-Series Truck Brochure.

6.9L IDI Aspiration

The 6.9L International Diesel Engine is naturally aspirated, meaning it relies solely on the air intake for the combustion process. This engine lacks a turbocharger which partially contributes to its sluggishness and lower performance when compared to Ford diesel trucks that came later down the road. Naturally aspirated engines have been around for a long time, and there are some advantages to having one. The lack of a turbocharger results in zero turbo lag. Instead, you receive steady power through the entire powerband. Today, we see many naturally aspirated motors, even diesel ones, being replaced by smaller displacement engines with a turbocharger or two. This is because smaller engines using a turbocharger can meet emissions standards easier, and produce tremendous power while simultaneously providing solid fuel economy. Just look at Ford’s 2.7L or 3.5L EcoBoost.

Banks 6.9L IDI Diesel Sidewinder turbocharger kit
The Banks Sidewinder Turbocharger kit is one of the most common 6.9L IDI Diesel Performance Upgrades. Image taken from the Banks Website.

6.9L IDI Fuel System Specs: Indirect Injection

The 6.9L IDI has an indirect fuel injection design. That means that fuel is injected into a pre-chamber, or swirl chamber. There, air and fuel mix together before they are forced into the combustion chamber. Despite being inefficient compared to modern direct injection system, these engine’s provided significantly better fuel economy than the gasoline engines offered by Ford at the time, like the 7.5L V8.

International’s 6.9L IDI diesel engine uses a reliable Stanadyne DB2 rotary injection pump for fuel injection. These injection pumps have proven themselves to be very reliable. As long as you stay on top of fuel filter changes and get good quality fuel, they can last a long time. The Stanadyne DB2 can actually be tuned up for small performance gains too as it’s one of the most common 6.9L IDI performance upgrades. If you choose to do this mod, just make sure you purchase an EGT probe and gauge set-up so you can monitor your Exhaust Gas Temperatures.

The Stanadyne injection pump delivers high pressure fuel to the hydraulic pintle style injector nozzles which then atomize this fuel into the cylinder head for combustion. These injectors, when new, will pop at around 2,100 psi. As they get older and begin to show wear, they will begin to open at lower pressures. Luckily the 6.9L IDI injectors are way cheaper than the complex electronically controlled injectors found on modern diesels. A complete new set can be purchased for around $400.

6.9L IDI Diesel Engine Specs

Years:1983-1987
Engine Design:V8
Displacement:6.9 Liters or 420 cubic inches
Bore:4 inches or 101.6 mm
Stroke:4.18 inches or 106.2 mm
Cylinder Head:Cast Iron; 5 bolts per cylinder
Engine Block:Cast Iron
Connecting Rods:Forged Steel
Pistons:Aluminum Alloy
Camshaft:Forged Steel
Crankshaft:Forged Steel; induction hardened
Firing Order: 1-2-7-3-4-5-6-8
Compression Ratio:
1983
1984-1987
See Below
20.7:1
21.5:1
Fuel Injection:Indirect fuel injection
Stanadyne DB2 Rotary Injection Pump
Mechanical Pintle Nozzle Injectors
TurboCharger:None
Valvetrain:OHV, 2 valves per cylinder
Aspiration:Naturally Aspirated
Transmission(s):3-Speed Select Shift Automatic Transmission
4-Speed Manual Transmission
Engine Oil Capacity:
(With Filter Change)
10 Quarts or 9.3 Liters
Cooling System:
Operating Temps:
Pressurized Series Flow
188-195 Degree Fahrenheit
Fuel:Diesel
Fuel Capacity:16.5 or 19 Gallon Front
19 Gallon (Behind Axle)
Horsepower (Varies):
1983
1984-1987
See Below
161 Horsepower @ 3,300 rpm
170 Horsepower @ 3,300 rpm
Torque (Varies):
1983-1986
1987
See Below
307 lb-ft @ 1,800 rpm
315 lb-ft @ 1,400 rpm

6.9L IDI Diesel Transmission Specs

Two transmissions are used in the 6.9L IDI, the T19 BorgWarner 4-speed manual or Ford’s C6 SelectShift 3-Speed Automatic transmission.

6.9L IDI Diesel Towing Specs

The 6.9L IDI Diesel Towing specs listed in the charts below are based on the 1986 model year. When loading a trailer on your Ford F-Series truck with the 6.9L International Harvester Diesel engine, make sure you check your owner’s manual or verify tow capacity through another means. Tow capacity can be affected by any modifications and it’s better to be safe than sorry! If something is listed as “N/A” that particular cab configuration isn’t available with the model of truck in 1986. These tow ratings come from the 1986 Ford F-Series towing guide and apply to conventional and 5th-wheel/Gooseneck towing. Max tow capacity for F-Series trucks with the 6.9L IDI Diesel engine is 9,400 pounds.

Ford 6.9L IDI Towing Specifications
Image taken out of a 1984 Ford F-Series Truck sales brochure

Max Tow Capacity (Auto Trans)

This tow rating chart applies to F-Series trucks with the C6 3-Speed Automatic Transmission and 6.9l Diesel engine.

ModelsRear Axle
Ratio
Max GCWRRegular
Cab
Extended
Cab
Crew
Cab
F-250 HD 4×23.08
3.55
4.10
10,500 lbs
12,000 lbs
14,000 lbs
5,600 lbs
7,100 lbs
9,100 lbs
5,000 lbs
6,500 lbs
8,500 lbs
N/A
F-250 HD 4×43.08
3.55
4.10
10,500 lbs
12,000 lbs
14,000 lbs
N/A
6,600 lbs
8,600 lbs
N/A
6,100 lbs
8,100 lbs
N/A
F-350 4×43.08
3.55
4.10
10,500 lbs
12,000 lbs
14,000 lbs
N/A
6,600 lbs
8,600 lbs
N/AN/A
5,900 lbs
7,900 lbs
F-350 4×23.08
3.55
4.10
10,500 lbs
12,000 lbs
14,000 lbs
N/AN/A4,800 lbs
6,100 lbs
8,100 lbs
F-350 4×2 DRW3.08
3.55
4.10
10,500 lbs
12,000 lbs
14,000 lbs
N/A
6,800 lbs
8,800 lbs
N/AN/A

Max Tow Capacity (Manual Trans)

This tow rating chart applies to F-Series trucks with the 4-Speed Manual Transmission and 6.9l Diesel engine.

ModelsRear Axle
Ratio
Max GCWRRegular
Cab
Extended
Cab
Crew
Cab
F-250 HD 4×23.08
3.55
4.10
9,200 lbs
12,000 lbs
14,000 lbs
4,300 lbs
7,100 lbs
9,100 lbs
3,700 lbs
6,500 lbs
8,500 lbs
N/A
F-250 HD 4×43.08
3.55
4.10
10,500 lbs
12,000 lbs
14,000 lbs
N/A
6,600 lbs
8,600 lbs
N/A
6,100 lbs
8,100 lbs
N/A
F-350 4×43.08
3.55
4.10
10,500 lbs
12,000 lbs
14,000 lbs
N/A
6,600 lbs
8,600 lbs
N/AN/A
5,900 lbs
7,900 lbs
F-350 4×23.08
3.55
4.10
10,500 lbs
12,000 lbs
14,000 lbs
N/AN/A3,400 lbs
6,100 lbs
8,100 lbs
F-350 4×2 DRW3.08
3.55
4.10
10,500 lbs
12,000 lbs
14,000 lbs
N/A
6,700 lbs
8,700 lbs
N/AN/A

6.9L IDI Model Year Changes

IDI Diesel Changes
1983– Ford 6.9L IDI Introduced
1984– 6.9L IDI Block replaced
– Compression Ratio increased from 20.7:1 to 21.5:1
– Performance numbers increased
1985N/A
1986– Last Year of Bull-nose Body Style
1987– Last Year of 6.9 IDI
– Body Style Change

Learn More About the 6.9 IDI

Want to learn more about Ford’s 6.9L IDI Diesel F-Series pickup trucks? Visit some of our other resources by clicking on the links below.

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ABOUT Kamil

Founder of Diesel Resource and a complete diesel head. Has a little bit of problem buying too many trucks. Learn more about him by checking out his truck.