Tom Wilson
February 16, 2010
Photos By: Dale Amy, Courtesy of Ford Motor Company

The Short-Block
Because a major mandate of the Coyote program was utilizing Ford's existing V-8 mass-production capabilities, and because 5.0 liters was considered the appropriate displacement, the jumping-off point for the Coyote was the closest existing engine, the Three-Valve 4.6 V-8.

There was no requirement to save anything of the 4.6 in the Coyote other than it must be suitable for production on the same machinery. As primary goals were the Coyote be stronger, more compact and powerful than the 4.6, it was a given that almost nothing from the 4.6 would carry over to the Four-Valve 5.0 TiVCT. Essentially nothing did, except the 4.6 bore spacing and its inherent limit on bore diameter.

Bore spacing is critical in the modular engine family-all modulars use 100mm (3.937-inch) bore spacing-because bore spacing and right bank leading are the major non-adjustable features of Ford's block machining line at the engine plant. In fact, bore spacing is likely the defining characteristic of the modular engines. They got the name "modular" because they were conceived in the '80s as a family of engines the assembly plant would sense as nearly identical and thereby allow rapid flexibility in their production. Thus, a modular could be a V or inline four-, six- or eight-cylinder engine, and any one of those engines could be built on Ford's engine lines with just a few hours of change-over time. In some cases similar engines could be built at the same time on the same line in random order, such as is done with 4.6 and 5.4.

Given all that, the new 5.0 was going to have a 100mm bore spacing and claim its place as the newest member of the modular family even though in nearly all other respects it is an all-new engine.

Of course, the Coyote team was as intent on giving its performance engine the maximum possible bore diameter. A large bore allows better breathing because it unshrouds the valves, plus it supports higher rpm operation because more of the displacement is in the bore and not the stroke so piston speed can be conserved.

Therefore, the Coyote team turned to the pressed-in iron cylinder liners in the Coyote's aluminum block. The critical decision was to get the liner as thin as possible for the largest possible bore, but not so thin it would be weak. In the end, that measurement was 92.2 mm, or 3.263 inches. This is 2.0mm larger than the 4.6 bore, a dimension taken mainly out of the cylinder liner and not the block.

Stroke was driven by the compromises inherent in reaching the desired 5.0 displacement such as keeping the engine physically compact (low and narrow), moderating piston speed, leaving room for ring packaging and so on. The Coyote team elected to retain the 4.6's deck height, and a 92.8mm (3.653-inch) stroke was selected to reach 5.0 liters.

To put the 5.0's short-block architecture in perspective, here it is compared to the familiar 4. 6 and 5.4 modulars:
Bore Spacing 100.0 mm(3.937 inch)100.0 mm(3.937 inch)100.0 mm(3.937 inch)
Bore90.2 mm(3.544 inch)92.2 mm(3.623 inch)90.2 mm(3.544 inch)
Stroke90.0 mm(3.537 inch)92.8 mm(3.653 inch)105.8 mm(4.165 inch)
Deck Height227.0 mm(8.937 inch)227.0 mm(8.937 inch)256.0 mm(10.079 inch)
Con Rod Length c-c150.7 mm(5.933 inch)150.7 mm(5.933 inch)169.1 mm(6.658 inch)
Rod-to-Stroke Ratio: 1.671.621.60

Note how there is an even 400cc increase in displacement with each engine, but how the 5.4 requires a taller and wider engine (deck height) to accomplish its increase over the 5.0. This is the tradeoff in being married to the 100mm bore spacing.

Keeping the same bore spacing also partially drives dimensions in the crankshaft and main bearings. Lowering friction is another major concern with the Coyote's 7,000-rpm redline, so the impetus was not to increase bearing diameters or widths. Existing 4.6 bearing sizes proved bulletproof and the Coyote crankshaft shares journal sizes with the 4.6 crank. In fact, the aluminum bearing shells are direct carryovers from the 4.6. No fancy tri-metal or copper bearings were required, so that was one less thing to re-invent.

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