Tom Wilson
May 6, 2011

Three-Valve 4.6

We’ve been surprised we don’t see more Three-Valves in pre-S197 Mustangs. The Three-Valve is an excellent performer and readily available; it would seem the cost-effective modular swap for pre-’05 Mustangs. It’s definitely lighter and easier to work around than the bulky Four-Valve engines, not to mention far less expensive. Slipped into a lighter chassis (anything is lighter than the S197), the Three-Valve promises never-get-tired-of-it thrust.

Paul’s High Performance ( has performed every engine swap mentioned in this article more than once, and main man Paul Svinicki says the Three-Valve performs nearly as well as a Four-Valve. Unless you just have to have a Four-Valve, Paul assures us that the Three-Valve is easily the better choice for most people.

What seems to have happened is the suave new S197 Mustang is so nice that, once again, it’s made more sense to simply buy an ’05-’10 Mustang instead of swapping its engine into an earlier car. That, and what engine swaps that have taken place were the Four-Valve 4.6 Cobra engines--Terminators or more likely Mach 1, Marauder, and early naturally aspirated Cobra engines just because they’re sexier.

Not incidentally, we’re also getting into a more complex swap because the Three-Valve has an electronic throttle and provides no idle circuit along with variable cam timing, and thus a different wiring harness and computer, plus the exhaust ports differ from the Two-Valve’s. This complicates the swap when back-dating into the less sophisticated SN-95s and seemingly pre-historic Foxes. For years Logan Motorsports has had the answer with a kit that addressed these concerns, but at the price of locking-out the variable cam timing and a cable throttle body. Now Ford Racing has its Control Pack for the Three-Valve. It keeps the desirable variable cam timing (better torque, fuel economy), but at a cost of $1,350. You may also still want Logan’s exhaust adapters to mate the Three-Valve ports with Two-Valve manifolds or headers that fit the S197, which might require moving a bung or EGR tube.

Mechanically the Three-Valve’s modular bellhousing and engine mounts are totally different than the Foxes’ pushrod pieces, so you are really redesigning the powertrain in that swap. Putting the Three-Valve into the SN-95 is less difficult because it’s at least a modular-to-modular swap, so transmission fitment requires no adapters. Ultimately this is a compelling, cost-effective swap that seemed destined to be overshadowed by either the Four-Valve Cobra or later Coyote 5.0 swap, but it should gain ground now that FRPP is offering a complete support kit in the Control Pack.

Four-Valve 4.6

Once again we’re talking about re-creating a car that Ford already built in the ’96-’01 Cobras and Mach 1s. So if a Mach 1, early Cobra, or Marauder engine came your way, you could swap it without much difficulty. The result is a nice bump in power, with a smooth-driving 315 hp or so from a Mach 1 Four-Valve. Technically the naturally aspirated Four-Valve engines swap without much trouble into the ’96-’04 GTs. Most of the connectors are the same for the injectors, oxygen sensors, mass air, timing pickups, and more, so wiring hassles are few. The six-bolt bellhousing pattern of a Mach 1 or Marauder is also a bolt-in. More good news is the exhaust, oil pan, throttle cable, and GT computer will work with the Four-Valve. This is a good swap when planning on pumping up the Four-Valve with a blower, nitrous, and so on.

Terminator 4.6

At some point an engine swap goes from an interesting challenge to impossible for the home mechanic, and that line lies between the naturally aspirated Three-Valve 4.6 and Terminator Four-Valve swaps. There are two reasons the exciting supercharged ’03-’04 Cobra engines are beyond the capabilities of a home garage enthusiast--the engine’s physical size and the complexity of its electronic controls. Together these make swapping the Terminator into an earlier Mustang daunting. While it can be done, but it is often too expensive and too encompassing for the average guy.

But as noted, it can be done. On the physical size standpoint, you’ll need Hydraboost (or manual brakes) to clear the valve covers, you’ll want the Terminator’s gas tank and fuels pumps, and you’ll find plenty of fabrication work hanging the charge cooler radiator, relocating the radiator, making a rear transmission mount, an so on. Electronically the Terminator wiring runs to the instruments, the transmission, and as far away as the taillights, with GEM and fuel pump modules previous cars don’t have.

In short, installing a Terminator in an earlier Mustang is pretty much installing an ’03 Cobra’s brains and mechanicals into the bodyshell of another car that wasn’t particularly designed to accept it. It is definitely a pro job.

All of this adds up. A Terminator engine is about $8,000; the transmission, $4,000; and it takes 60 to 100 hours of pro labor to put it all together. That’s another $8,000 or so, and that doesn’t begin to include the upgraded suspension, brakes, blowers, fuel systems, sound systems, and other stuff such massive projects tend to attract.

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