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Mustang 5.4L Engine Swap - Size Matters
What If Ford Had Put A 5.4 In The Mustang? An Engine Swap Gives You An Idea--And A Lot More Torque
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.
The 5.4 intake is wider and the factory intakes that are available are far from ideal. The trucks have plenty of room on top of the motors, so Ford makes no attempt to keep the height down. In addition, the throttle bodies are pointed in different directions and sensor locations are different. The E-150 van has a shorter height intake due to its more cramped engine bay, but it is still quite tall. Its long runners are designed to make the kind of torque curve that truck owners appreciate, but that would make sports car owners feel as if-well-they had a truck motor.
After some careful measuring, it was determined prior to this project that the stock 4.6 intake could be reused if some custom adapters were made to allow it to bolt to the wider 5.4. It would all fit (hopefully-since the spouse was told it would) under a stock hood. There are several benefits to this method, the most important being that the fuel rails, the injectors, the sensors, and the throttle body are all in their same relative positions and will require no modification to reconnect them. When it comes to swap simplicity, this is a huge plus.
Another benefit is that using the same intake as the 4.6 will keep us as close as possible to the initial goal of seeing what power gains the bigger short-block is worth by itself. The P.I. ("performance improved," in Fordspeak) cylinder heads on our 5.4 are identical to those installed on '99-and-up Mustangs, as are the cams. Apparently all P.I.-headed vehicles, whether car or truck (even Lightning), wear the same cams.
We will be using the complete 4.6 exhaust, including headers and stock cat H-pipe. The front of the airpath from the filter through the throttle body will remain unchanged. This gives us as similar a configuration as can be achieved between the two motors, with the notable and regrettable exception that the intake adapters will add approximately 1 3/4 inches of runner length to the 4.6 intake manifold. We say regrettable because the intake will already have a lower peak-power rpm when installed on the larger motor, as compared to what it peaked at on the 4.6, and the additional runner length will lower that peak a bit more. For now, however, this is as equal a comparison as possible, and a shorter runner and higher flowing intake will be tested later on.
Many thanks go out to Brian Ebert at HiTech Motorsport for his help on the project. Without his tuning prowess, our results would not have been nearly as successful-check the dyno charts to see why. Now follow along with the pictures and captions as we go big or go home.
The van that previously held the 5.4 required a relocated oil filter, so the casting that contains the oil-filter mount and lower radiator hose connection was pulled off the 4.6 and installed on the 5.4. The gasket for this (along with most others on the motor) was reused, as the newer-design gaskets with a plastic body and rubber O-rings around the sealing areas do not crush as do older-style gaskets, and can be used many times.
The dipstick tube was reshaped just a bit. A new hole drilled in the bracket allowed it to bolt to the same mounting spot on the head as before. Above the rightmost exhaust port, the head has the letters P.I. cast into it-an easy place to look if you're trying to determine whether or not a potential donor has the newer motor.
While both motors were out and acces-sible, the cams were measured to make sure they were the same. Both measured at 0.282 intake and 0.297 exhaust lobe lift, or 0.508/0.535 max lift at the valve. All P.I.-headed modulars, whether car, truck, or van, reportedly have the same cams, so you shouldn't have to worry about swapping the Mustang cams.
Shown here are the nearly completed adapters installed on the 5.4, with some of the bolt holes yet to be drilled and tapped. You can see on the top adapter that the coil packs stay in their original location and will now bolt to the adapter. The fuel injectors stay in the intake manifold as before. With the adapters in place, any 4.6 manifold will bolt right on, giving us the flexibility to make a future change without having to wait for a company to come out with a 5.4-specific Two-Valve intake.
Here is the 4.6 intake installed on the 5.4 with the custom adapters. The air and water passages angle through the adapters to bring them into alignment with the narrower 4.6 intake manifold. The adapters first bolt to the heads with recessed-cap head bolts, and the intake then bolts to the adapters. After many hours on the mill, it was a good feeling to put it all together for the first time and have everything line up perfectly!
The 4.6 flexplate had a slightly smaller-diameter torque converter bolt pattern, and was swapped onto the 5.4. Because engine balancing is not done with the flexplate, they are interchangeable as long as you have an eight-bolt Windsor 4.6 and not a six-bolt Romeo. In this case, it would have been nice to notice the slight difference in bolt pattern while the motor was still out of the car, rather than while reinstalling the transmission (the first time).
Due to the extra 1.6-inch width, installation was quite a challenge with the A/C lines on one side, the brake booster on the other, and the ABS module in front. Repositioning the hoist to tilt up the front of the motor finally allowed it to slip in, but it would have been advantageous to have a hoist with tilt capability for this installation.
Once the 5.4 was set into place, there was plenty of clearance everywhere except for the passenger-side header. The header's casting had a lump on the outside that had nothing to do with its function. The lump was touching the framerail and needed to be removed. Jacking up that side of the motor a bit allowed us to grind off the lump, with the motor in the car. Once this was done, there was approximately 3/8 inch clearance to the framerail. This operation would be much easier to do beforehand on the engine stand.
The 5.4 is approximately 0.8 inch wider on each side, and the cylinder heads sit 0.8 inch higher than before. This means we'll need a wider H-pipe. It also means the exhaust is being pulled closer to the floorpan.
To make the necessary changes, the stock H-pipe was cut in half at the cross-over, and the passenger side was modified as shown above.
Although it now sat closer to the floorpan, the driver-side half of the H-pipe still had plenty of clearance. However, due to the changes in the passenger-side half, it needed to be lengthened 1 inch to bring the crossover back into alignment.
Rather than welding it, the H-pipe crossover was reconnected with a short piece of pipe and exhaust clamps, to ease removal and installation in the future. As wide as the H-pipe is now, it may be necessary to separate or at least loosen the halves to get it in and out.
One of the heater hoses no longer fit, and bending it caused it to fold and kink.
The fix turned out to be as easy as browsing the hose wall at a local parts store until one was found that was a perfect replacement. There is a metal flow restrictor in the stock hose, so be sure to cut it out and slide it into the new hose.
The throttle body now sits almost 2 1/2 inches higher. The initial measurements showing it would clear were correct, but the linkage behind the throttle body had not been accounted for. Removing a section of the underhood bracing gave plenty of clearance.
The new motor looks like a factory install--as it should since almost everything visible was unchanged. The next time the aluminum intake adapters come off, they will be powdercoated black, so it will take a keen eye to notice it isn't just another 4.6 sitting there.
Before beginning the swap project, we went to HiTech Motorsport to get some baseline numbers with the 4.6. The only modifications to begin with were a K&N air filter and Flowmaster three-chamber mufflers. The mufflers are likely giving us no power, however, as the stock 2 1/4-inch tailpipes are currently stuck back in the outlets and welded in place. The project car has a 4R70W auto trans, and the horsepower and torque numbers fell in right where they should have.
Quite surprisingly, the air/fuel ratio was spot-on during the baseline runs, hovering right around 13:1 through the entire pull. We went back a couple weeks later with the 5.4 in place and running fine, but as you can see in the 5.4 baseline runs, the computer was in definite need of some help dealing with the extra cubic inches and airflow. The torque curve started out with some nice gains, but by 4,000 rpm it was falling fast and ended up well below our stock 4.6 baseline.
With the baseline recorded, Brian set to work seeing what he could wring out of it. The bigger motor was running somewhat rich with air/fuel ratios in the 12.3:1 range, so the first thing addressed was to get that back up around 13:1. Brian then straightened out the factory timing curve, and we began adding timing by changing the base number (similar to turning the distributor on a 5.0). Our motor ended up liking 14 degrees initial up top, but it made a bit more torque down low at 12 degrees initial, so the timing curve was reprogrammed to reflect that. Brian also turned off some of Ford's torque-management features and took away most of the tip-in spark retard to aid in throttle response. That last change didn't show up on the dyno, but it made a huge difference when driving the car.
After the tuning was finished, we had big gains all over the curves, but the biggest difference was in carrying the torque curve out further. From 4,500 all the way up to 5,750, we picked up around 30 hp just with the tuning. And instead of falling below the 4.6 baseline near 4,000 rpm, we now had solid gains all the way up to around 5,600 rpm. At that point there was just no getting past the extremely long runner length of the stock 4.6 intake. There are ways to get around that in the future, with either an intake or cam change, but we were confident we'd gotten all the power that was available without further modifications.