Tom Wilson
June 1, 2013

Coyote Into Fox/SN-95

Taking top billing on the Ford engine swap scene is the Coyote-to-Fox transformation and there’s no mystery why. The engine is excellent and available, and the classic Fox chassis is many hundreds of pounds lighter than the bloated S197 the Coyote is naturally found in.

Coyote/Fox marriages are excellent performers, with a modern, revvy feel. There’s no immediate need to hot rod the Coyote engine as it has 412-420 horsepower out of the box and plenty of torque (390 lb-ft) to move the sly Fox with authority. Choosing the SN-95 does mean adding around 150 to 200 pounds of extra weight, depending on the cars being compared, but it’s still lighter than the S197 and a little stiffer in the chassis than a Fox.

Adding a power adder makes things better in a straight line, but for an all-around driver, we prefer to preserve the Coyote’s light all-aluminum vibe in naturally aspirated form. But don’t let our tastes stop you! A power-adder Coyote Fox sounds like mega-fun, too.

Three-Valve Into SN-95

If it weren’t for the Coyote, the 300hp Three-Valve ’05-’10 Three-Valve Mustang GT engine would be the hottest Ford swap going. This is still a great engine with far better performance than the ubiquitous Two-Valve fodder in ’96-’04 Mustangs. It’s lighter, more powerful and best of all, nearly a drop-in replacement for aging Two-Valve Mustang GTs.

Three-Valves are an especially good swap for the anemic ’96-’98 Two-Valve GTs because the Three-Valve can add almost 100 hp to these under-powered Mustangs. Even the Performance Improved ’99-’04 GT’s gain about 40 hp with a Three-Valve replacement, which is a bump you can feel. And, if the budget allows, the Three-Valve is a great blower motor; you’ll really enjoy the rowdy torque and top-end charge a simple positive-displacement supercharger puts into these engines. In our September 2009 issue we reported on the ’10 GT Ford Racing built as a demonstrator with a Whipple and just 5 pounds of boost. With 400 hp, 400 lb-ft, and 3.73 gears it was a riot. More importantly, it’s something the average enthusiast can aspire to—and build himself as paychecks allow.

When sourcing a Three-Valve, make sure you get a Mustang GT variant with an aluminum block, and not the iron block version from the Explorer and Explorer Sport Trac. In any case, Ford Racing doesn’t carry these engines, so they are wrecking yard parts these days.

Today Logan Motorsports owns the Three-Valve swap market (see Do The Math, p. 91) with its complete swap kit at $1,499 in standard form or $1,899 with an SCT tune. Logan says ’96-’98 owners need a $499 fuel-rail conversion kit, and because their kit does not support the Charge Motion Runner Control operation you can either buy CMRC delete plates or let Logan modify your CMRC plate for $100 on an exchange basis.

Another resource is Ron Francis Wiring (, which just released both full-car wiring kits and engine/transmission wiring harnesses for Three-Valves. These harnesses will set you back about $950 to $1,000 depending on the transmission, but they’re a lifesaver if all you have is an engine and no donor car. They also have full Fox-chassis wiring harnesses.

A pioneer in the Coyote-Fox swap business, S&R Performance ( created this alternative to the FRPP power steering pump bracket, which also allows adding air conditioning. At $595 it’s considerably more expensive than the FRPP part, but it mounts the stock ’96-’04 PS pump in the stock location for those cars, allowing use of the stock Hydroboost lines. This retains stock brake pedal and steering feel.

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Overlooked only because everyone is goofy for Coyotes (can’t blame ‘em), the Three-Valve 4.6 remains a fine performance engine. Unlike the bulkier Coyote, the Three-Valve slips into SN-95 Mustangs using its stock oil pan every time.