BACK IN THE DAY

a Garrett wastegated turbo with an A/R of 0.82. Advertised power and torque were 190 hp and 385 lb-ft, but this engine was somewhat underrated. If you look at the nearby power chart, you will see it’s mysteriously cut off at 3,000 rpm vs. the NA engine going to 3,300. The power line looks to still be climbing at 3,000 and extrapolations show the turbo engine was somewhat over 200 hp at 3,300. Speculation within the IDI enthusiast community is that with the new 210hp Power Stroke engine on the horizon Ford marketing wanted to make sure the new engine looked “better” than the old one. The IDI turbo engine was hyped more for its high-altitude performance than its raw power, but tweaking in the intervening years has shown that the IDI turbo is fully capable of 250 hp with only minor tuning.

Internally, the IDI turbo was given improved head gaskets with a heavier fire ring. The pistons were given keystone rings and anodized crowns. The wrist pin diameter was increased from 1.110 inches to 1.308 inches. Inconel exhaust valves were added and the oil cooler bundle was increased from 24 fpi (fins per inch) to 30. The injection pump calibration was altered and new injectors were used. Minimum boost was 5 psi but most developed around 8-10 psi in service.

The Turbo IDI and the Power Stroke shared the stage in ’94 and sales overlapped a little after the PSD’S mid-year intro. In reality, the Power Stroke is very much the IDI engine’s progeny. Especially in the first-gen PSDS, the IDI heritage is pretty clear and there are even a few interchangeable parts.

The IDI Today

Nearly 1.5 million 6.9L and 7.3L IDI engines were produced by International Harvester and its offspring, Navistar International. They are truly one of the cornerstones of the growth of diesel power in pickups. The IDI is an old-school engine and can’t hold a candle to the modern electronic engines in the power department, yet it has a large following. There are still gobs of them on the road, some still even in commercial livery. And they just go on and on. One IDI diesel fan has been heard to say, “This thing will have parts availability until the sun runs out of hydrogen!” That may be an exaggeration, but the IDI Ford is nowhere near the end of the road.

 The pinnacle of the Ford IDI was the 7.3L IDIT turbo engine. It was advertised at 190 hp and 385 lb-ft, but is generally considered to have been underrated and undertuned by Ford so as not to upstage the upcoming Power Stroke. It was a considerably...

 The top of the line was XLT, to which “Lariat” was added. Shown here is Frank Butt’s ’86 F-250HD 4x2 Supercab, bought new by him in ’86. Besides the regular-cab longbed and the Supercab, Ford offered a crew cab version.

 The Ford diesel was in full swing when this ’84 F-250HD 4x4 XL debuted. In this era the XL was a step up from the base model and sat in the middle between the base and XLT (later XLT Lariat) models. The “HD” in the designation denoted the 8,600-pound...