Medium-duty truck buyers are due for a potential treat when Ford Motor Co. launches 2011 models of its Super Duty F-Series next spring powered by the company's all-new Power Stroke 6.7-liter V8 turbodiesel.

The new, in-house-developed engine ends Ford's decades-long supply arrangement with Navistar International Corp., a relationship that ends this year after a long and publicly nasty dispute.

The engine, which chief engineer Adam Gryglak said is a total clean-sheet design, is something of a technical tour de force: it has an innovative twin-turbocharger setup packaged as a single unit, a reversed exhaust-port design in which exhaust exits on the inner portion of the engine's vee and Ford's first medium-truck use of weight-saving compacted graphite iron for the engine block.

The all-new Power Stroke will go into production next spring at Ford's Chihuahua, Mexico, powertrain facility. During a media information session, engineers declined to give official power and torque figures, but Edmunds.com's Inside Line last week obtained the figures from a Ford source: 400 horsepower and a rather outsized 725 lb.-ft. of torque.

That compares with 350 horsepower and 650 lb.-ft. of torque developed by the current Power Stroke, a slightly smaller 6.4-liter V8 turbodiesel built by Navistar International Corp. Ford had for some time been embroiled with Navistar in a contentious and damaging supply-agreement and warranty-obligation dispute regarding the Power Stroke, which despite a generally outstanding reputation, had in a previous generation as a 6-liter V8 suffered reliability problems for which customers in the heavy-duty pickup market have little patience.

Despite the Power Stroke's recent bad press with consumers, Ford nonetheless has retained 60 percent of the medium-duty truck market, say company engineers, who expect the new engine's power and efficiency to win back potentially skeptical customers. Diesel engines have long accounted for the majority of medium-truck sales because their load-pulling torque and longevity are highly valued by commercial users.

Those attributes mean diesels, which can command price premiums approaching five figures, also are jealously guarded profit machines for the automakers, who compete fiercely in the segment.

In the earlier part of the decade, Ford, General Motors Co. and the Chrysler Group LLC had engaged in a power war with the medium-duty diesel engines as new technology such as common-rail fueling and direct injection vastly improved performance, economy and NHV characteristics. GM's current Duramax V8 turbodiesel was developed and built in a joint venture with former partner Isuzu Motors Ltd. Chrysler's medium-truck diesel, an inline 6-cylinder, is supplied by Cummins Engine Co.

Ford's 2011 Power Stroke is placed to whip both. The current Duramax makes a maximum of 365 horsepower and 660 lb.-ft. of torque for GM's Chevrolet Silverado HD and GMC Sierra HD. The Cummins-made 6.7-liter turbodiesel I-6 develops 350 horsepower and 650 lb.-ft. of torque for the Dodge Ram 2500/3500. - Bill Visnic

The engine, which chief engineer Adam Gryglak said is a total clean-sheet design, is something of a technical tour de force: it has an innovative twin-turbocharger setup packaged as a single unit, a reversed exhaust-port design in which exhaust exits on the inner portion of the engine's vee and Ford's first medium-truck use of weight-saving compacted graphite iron for the engine block.