Tom Wilson
September 1, 2004

Horse Sense:
Back in the '60s, Ford built 427, 428, and 429 big-blocks all in the same year-and you couldn't blame a then-new enthusiast for wondering why. Now the newbie might wonder what the difference is between a 5.0 and a 5.1. The answer is "everything." There is no engine swap taking place, so things such as exhaust systems, sensors, wiring, hood clearance, and all that small-but-bothersome jive are not an issue

Modular engines have their defenders and detractors, but nearly everyone agrees it wouldn't hurt if the things displaced a few more inches. Size matters and all that, and with only 281 ci of working volume, the standard 4.6 Mustang engine has to rely on plenty of technique, efficiency, and plain-old charm to thunder with the rest of them.

True, there is the 5.4 V-8 with its willing torque and generally power-happy disposition compared to its little brother. But 5.4s are tall and wide and don't fit quite as naturally in Mustangs. Putting a 5.4 into a Mustang means an engine swap with its attendant hassles, a consequential weight increase, a shift upward in the center of gravity, a dearth of good intake manifolds, more cramped exhaust, and-well-you get the idea. The 330 ci are great, but they're a bit of a pain to gain.

Enter the stroker option. Made popular by 347 pushrod engines, strokers have come to dominate the Fox Mustang scene at rebuild time. It costs almost no more to re-engine with a 347 than a 302 these days, and modular engine builders have been studying the situation so they can do the same with the modular engines. One of those engine builders is Coast High Performance, which has just released its newest family of short-blocks, featuring a 5.1-liter derivative of the 4.6.

Advantages of the stroker 4.6 concept are many. There is no engine swap taking place, so things such as exhaust systems, sensors, wiring, hood clearance, and all that small-but-bothersome jive are not an issue. Intake manifolding options for the 4.6-based engines are, if not numerous, still distinctly better than for 5.4s. There is no weight gain or shift in center of gravity. Outwardly the engine remains visually a 4.6, so no one has to know what you've done. And now, the swap has been made easy with off-the-shelf parts.

For a big engine firm such as Coast, some of those special parts are easy to make, but a few are essential because of either cost or complexity. So, while Coast doesn't sweat pistons because the Probe Industries arm of the same company is one of the largest specialty piston makers in the United States, and strong connecting rods are avail-able in any configuration from China, the stroker crankshaft is the key to the modular swap.

While stock 4.6 cranks can be offset-ground to stroker dimensions, the process is time-intensive and thus expensive. Worse, the surface hardening of the stock crank is thin and removed during the offset-grinding procedure. That means expensive hardening is needed.

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