By Richard Holdener/Photos By Author
Now that the 5.0L Coyote has taken center stage, few eyes are fixed on the 1996-2004 Mustangs. Truth be told, the 4.6L two-valve (2V) was introduced way back in 1991 in other Ford vehicles, but it wasn’t until 1996 that it found a home under the hood of America’s favorite pony car. When first introduced, the then-new modular was the first-gen, non Power-Improved motor, meaning it was rated at 215 hp.
This grew by 10 hp to 225-hp in the last iteration in 1998, but this was eventually replaced by what we would come to know as the Power-Improved (PI) version. Compared to the modern Coyotes that handily exceed 400 hp, the 260 horsepower offered by the 2V PI motors seems pathetic, but it was welcomed with open arms back in the day. The upgrade came courtesy of revised cylinder heads, cam timing and intake manifold. Even with the upgrades, the single overhead-cam motor was hardly a powerhouse, especially with the competition sporting extra displacement. Though Ford sold millions of these 2V-powered Mustang GTs, what they needed new, and continue to need as used vehicles, is more power.
As Ford learned when upgrading from the Non-PI to the PI version, the three major power producers on any motor are the heads, cam and intake manifold. Sure, the exhaust, compression and even things like ring seal all combine to make power, but the heads, cam and intake are the three heavy hitters. For this test, we will focus on adjustments to the cam timing.
In fact, the test motor was run with two different cam profiles from Comp Cams. Why two sets of cams you ask? Well, it’s certainly true that cam profiles are a major factor in the power production of a 4.6L 2V motor, but we wanted to show not just the extra power, but the trade off inherent in power that comes with ever wilder cam timing. You see, bigger cams, meaning those with increased lift and/or duration, can indeed improve power production, but there is a limit to just how much extra power you can get. In fact, not only is there a limit, but often times the extra power you get in one rpm range can actually cost you power in another area. There is no better way to illustrate this than by comparing mild and wild cam combos on the same motor.
Before we could get started with our cam test, we needed a test motor. Luckily, we had the perfect specimen in the form of our 1998 hybrid motor. What is a hybrid you ask? Well, our test motor started out life as a high-mileage, 1998, non-PI motor, but had been previously upgraded with PI-based, top-end components. The stock, non-PI heads were replaced by CNC-ported, PI heads from Total Engine Airflow. The Stage 2 heads featured full porting and chamber work to dramatically improve the flow rate of the stock castings. Because this motor would eventually see boost and nitrous, the ported heads were secured using ARP hardware and Fel Pro MLS head gaskets.
For our test, the ported PI heads were first equipped with a set of Comp XE262AH cams and matching beehive springs. The mild XE262AH cams offered .550 lift, a 226/230-degree duration split and 113 lsa. Both of our cam choices were run with the stock PI intake manifold, Accufab throttle body and a set of long-tube headers. After tuning the combination with the Fast XFI/XIM management system, the motor produced 377 hp at 5,900 rpm and 373 lb-ft of torque at 4,900 rpm. Now it was time for the wild cams!
To illustrate how cam timing changes the power curve, we decided to replace the XE262AH cams with wilder XE278AH grinds. Like the smaller XE262AH cams, the larger XE278AHs offered .550 lift and a 113-degree lsa, but the duration was up to a healthy 242/246-degree split. Installation of the bigger Comp cams required removal of the damper, front cover and valve covers. It was also necessary to remove the stock rockers before unbolting the cam towers.
Failure to eliminate the spring tension applied to the cam (and towers) may result in distortion to the tower or cam journal surfaces. We also took the liberty of bleeding the lifters to allow for easy assembly of the rockers once we installed the new cams in place. Though many enthusiasts fear cam swaps on an OHC motor, the reality is its as easy as any motor, and required only lining up the dots on the timing chains and sprockets. With our cams properly orientated relative to the crank, we reinstalled the rockers, valve covers and front cover. After installation of the damper, the big cams were ready for action.
That the new cams required tuning was a good sign, as it meant the power changed from the smaller XE262AH cams. Once dialed in with the FAST management system, the larger cams produced peak numbers of 395 hp at 6,000 rpm and 379 lb-ft of torque at 4,900 rpm. You will note that both of these numbers were improvements over the smaller cams. In fact, the bigger cams offered gains as high as 28 hp over the smaller grinds out at 6,500 rpm, but (as always) that extra high-rpm power was marching proudly in the trade parade, meaning it came with a loss in low-speed torque.
The smaller cams improved torque production over the larger cams by 13 lb-ft at 4,200 rpm. The question with these two cams is where do you want your power production? If this was for a race application, then the extra top-end surge would definitely be the way to go, but what about for your only means of transportation? Most daily drivers, even driven by performance enthusiasts, spend most of their time below 5,000 rpm and place a premium on drivability. For that application, maybe its not a good trade!