Muscle Mustangs & Fast FordsHow To Engine
Here's our first-ever buildup of a 4.6 Three-Valve modular engine--And it rocks.
For over a decade, the Ford modular engine program has been with us (in both Two-Valve and Four-Valve configura-tions). In 2005, Ford added a Three-Valve version to the Mustang mix. With regard to its Two-Valve and Four-Valve brethren, the aftermarket has moved forward to overcome many hurdles when it comes to dissecting the Mustang's modular powerplant and making it better.
With the introduction of the all-new '05 Mustang, we were faced with the next evolution of the performance modular engine in the form of a three-valves-per-cylinder setup on the cylinder heads. This was Ford's answer to better performance, increased fuel economy, and lower emissions. The camshaft is controlled electronically through sensors and oil relief valves--further complicating development of performance-enhancing aftermarket parts. The computer advances and retards the camshaft timing. One good thing out of all this is that Ford gave us 300 hp from the factory. That makes this the most powerful base Mustang GT of all time.
While variable cam timing is nothing new to the automotive world, it's weird science to crazy Mustang owners. To make matters more difficult, we have been burdened with a complex computer system to control the variable camshaft timing, among other elements. Would the aftermarket be able to overcome or enhance this new technology? The answer to that ques-tion is a resounding "yes." A few companies have already broken down the electronics barrier and have made great strides in tuning the computer system. Alas, as more enthusiasts modify their '05-up Mustangs, more parts get broken. But that is when we learn how to fix the Stang and make it better.
We hooked up with Justin Burcham of JPC Racing (Glen Burnie, Maryland) to get an inside look at his new engine combination. While most S197 Mustang owners at this point will not be replacing the engine, Burcham's move into this area will lay the groundwork for future projects.
Truth be told, the swap was necessitated after Burcham nuked the stock engine. One night this past August, the Maryland shop owner was on his way to a 9-second run when he missed Fourth gear. He got the transmission back into Fourth and screamed through the traps at 7,500 rpm. The car did run 10.29 at 136, but the severe horsepower (estimated 700-plus at the flywheel with the nitrous) did not bode well for the stock short-block. One of the connecting rods decided it wanted to see daylight, which effectively made the short-block a pile of junk within a few tenths of a second.
To be honest, we were surprised the stock bullet lasted for so long in a consistent 10-second ride. It made it through the spring and summer months with weekly trips to the dragstrip and chassis dyno, and let's not forget the street miles logged in that time. The unmolested engine performed quite admirably under such harsh conditions--read 560-plus rear-wheel horsepower with a ProCharger D1SC and a little nitrous to keep things insane. At the time, it was OE from the throttle body to the exhaust manifolds.
The Three-Valve short-block is extremely similar to the modular engines in the '96-'04 models, and the chain setup seems to be a direct carryover, as well. But the camshafts, cylinder heads, and intake manifold are vastly different. The bottom half of the engine was handled by Rich Groh Racing (RGR) Engines.
Groh used a '97 Cobra engine block, as they are supposed to be nearly identical to the Three-Valve engines, though a bit lighter and stronger. They were close enough, albeit there were a few minor issues with the motor mounts. JPC is working on motor mounts to retrofit the earlier modular blocks into your '05-up Stang. Custom CP pistons were chosen for their high quality and forged casting. They are custom-designed for a supercharged/turbocharged combination. The crank was sourced from an '03 Cobra engine and is made of steel. Eight Eagle rods connect the Cobra crank with the CP pistons.
Fox Lake Power Products handled the porting and polishing of the Three-Valve heads. Ron Robart and his crew already have a CNC program specifically designed for the Three-Valve heads. "I think there is more potential in these heads than the Four-Valve heads. The port shape is nice and it's raised up," Robart says. He also mentioned the angle of the ports make it more like a motorcycle head, and the exhaust ports are efficient as well.
The flow numbers may not be what people expect, but Robart wanted to point out the fact that the intake port is extremely efficient. That is because it has virtually a straight shot into the combustion chamber. Therefore, large flow numbers are not nearly as important in this application. When you have a severe bend in the port, like in the Four-Valve intake ports, you need to get the flow numbers higher. The exhaust may have half the amount of valves as the intake side, but Robart says the exhaust port has a great shape, making it very efficient as well. This could be Ford's best OEM head in terms of performance potential.
Fox Lake installed a set of Ferrea stainless steel valves, which measure the same as the stock pieces. They also upgraded the valvesprings to a double-spring setup. This is probably one of the best benefits because the engine will be able to rev higher and make more horsepower.
Unfortunately, there were a few components we would have loved to change, but at the time, nothing was available. The camshafts were left stock, but Comp Cams will soon be releasing several different grinds for these engines.
The other component we left stock was the intake manifold. We are not sure of the flow numbers, but the intake definitely looks a lot better than the OE Two-Valve piece. The runners are shorter to promote better breathing at higher rpm. The stock Two-Valve intake had to help create low-end torque because of the 4.6's small displacement. One would also think the Two-Valve engine would be a rev-monster, but that isn't the case because the manifold is restricting it. The Three-Valve engine may have the same 281 cubes, but the variable cam timing made a huge difference by creating a broader torque curve when compared to its Two-Valve cousin.
Ford did its homework, and this engine is more than capable of pulling serious rpm with the correct valvesprings in place. Burcham has turned 7,500-plus rpm (without valve float), and the intake manifold seemed to allow the engine to breathe deep enough to achieve it. He did report that optimum power with his new engine is around 6,900-7,000 rpm. This is with the stock camshafts in place, too. "I tried shifting 7,000 and higher with the stock engine, but the valvesprings were too weak and the engine would float the valves," Burcham says. Fox Lake fixed that problem with a stiffer set of springs designed for high-performance usage.
As a side note, we wanted to mention some observations in testing. Burcham spent some time at ProCharger with this car and found that the more boost stuffed into this engine, the lower the rpm of peak power. For example, 15 psi (565 rwhp) made peak power at 6,800 rpm, but 17 psi (585 rwhp) had a maximum horsepower rating at 6,500 rpm. At 20 psi (615 rwhp) of boost, the peak power rpm occurred at 6,200. This was with the stock engine, not the built engine with the better heads and valvesprings. Burcham attributed the rpm variances to the weak OE valvesprings not working properly with the large amount of boost (or cylinder pressure).
We would certainly like to do a cam swap in the future to see what the Comp Cams stuff is worth over the stock sticks, but that will have to wait until another issue. For now, we'll just reinstall the stock camshafts, even though it's something we know has to be limiting performance. After all, Burcham's engine does get stuffed with a lot of boost from a ProCharger D1SC blower, and it sometimes gets a whiff of nitrous when the big money is on the line.
With the engine together and the factory electronics still in place, it came time to tune the beast. Mike Carlson of ProCharger provided assistance in getting the tune-up correct. He worked with Burcham via phone and Internet to get the programs loaded into the car through a Predator handheld tuner. After sneaking up on the proper tune-up using an air/fuel meter, the car spun the Dynojet chassis to the tune of 640 hp and 544 lb-ft of torque (at the tires).
The car has also received numerous upgrades to the driveline to handle the extra horsepower. First on the list was a "real" transmission designed to take supercharged abuse. With assistance from a Swarr Automotive conversion kit, Burcham installed a Tremec TKO 600 five-speed transmission, an SFI-approved bellhousing, and a Centerforce clutch. A new JPC Racing one-piece driveshaft was also installed. The one-piece driveshaft saved 30 pounds in rotating weight and is stronger than the stock two-piece unit.
At the time of this writing, bad weather in the Northeast prevented any on-track dragstrip testing of Burcham's new bullet. But he is confident the horsepower is there to achieve a nine-second run in his full-weight street car--complete with air conditioning, stereo, and other amenities for life on the streets.