Diesel World - - Feature -

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 beefed-up en­gine, with beefier pis­tons and rods, a stronger block (cast­ing num­ber 10809000C3) and head gas­kets, In­conel ex­haust valves and a large oil cooler.

 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 GVW, the low­est GVW light truck in which the 6.9L diesel was of­fered.

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