Mustang 5.4L Engine Swap - Size Matters

Horse Sense: What did this swap cost, you ask? The 5.4 was found at a recycler for $1,150, and the stock motor brought in $450. All told, with miscellaneous gaskets and billet aluminum for the adapters, it was less than $900 to go from a 98,000-mile stock 4.6 to a 4,000-mile 5.4 with a lot more potential. We call that money well spent.

You've heard the saying "There's no replacement for displacement," right? It was a wise man who first uttered those words. We also know that as much as we like the newer Mustangs, perhaps the main drawback is that the engine is, well, to put it as p.c. as possible, "dimensionally challenged." OK, forget the p.c. stuff-this thing is small, and when the GM competition is packing an additional 68 ci, Mustang drivers are starting out in a fairly sizable hole.

Ford engineers have done an admirable job of tuning a broad torque curve out of the little guy, but there's still no way it will be doing any big-block impersonations at the next Christmas party. There are also many thousands of 4.6 Mustangs on the road that are getting up there in miles, so rather than just rebuilding the short-block back to stock performance levels, wouldn't it be great to pick up another 49 ci, as well as a fresh motor? That's the idea that got us swapping, snapping, and typing.

Options for increasing the size of the venerable 302, along with the substantial benefits that can be realized, have been documented many times, but modular guys for the most part have been left out in the cold. There are now stroker kits and big-bore blocks on the market, but they require a fairly hefty budget to be an option. The idea here is to see what some good old-fashioned automobile parts recycler (OK, junk-yard) engine swapping can do. There are plenty of low mileage 5.4-equipped pickups, Expeditions, and vans from which you can acquire a motor, and dropping in a bigger factory motor is as pure a hot-rodding idea as you'll ever come across. Mustang enthusiasts have been clamoring for a 5.4 SOHC GT since about the day after the first 4.6-powered Mustang was announced, so here's the chance to see what could have been.

Our plan is to first run the 5.4 in as equal a configuration as possible to that of the 4.6. We want to see how much gain the cubes alone are worth, as well as how well the factory induction pieces can handle the extra airflow demands of 330 rather than 281 ci. We will later see what the typical 4.6 bolt-ons are worth on the bigger motor. Finally, we'll get serious with ported heads, a short-runner intake to extend the rpm range of the motor, and most likely some hotter cams as well. Initially, we expect some large gains in torque with a small gain in peak horsepower, but as the modifications become heavier, the horsepower gains should also begin to shine.

For the most part, the 4.6-to-5.4 swap is straightforward-both are from Ford's modular engine family, meaning they share a large amount of componentry. The basic block architecture is the same. However, there is a difference in that-similar to the 302 versus the 351-the 5.4 has a taller deck height (distance from centerline of crank to top of cylinder bore).

The modulars are much more closely related than their pushrod cousins, though-the accessories mount in identical fashion, things such as oil pans are interchangeable, and they even use the same pistons. But the difference in deck height leads to the main problem with putting a 5.4 into a Mustang, and that's intake manifold selection.