Rob Reaser
September 1, 2001

It seems that just about every stock component of the 5.0 engine can be replaced with an upgraded aftermarket piece designed to boost power output. New 5.0 owners and novice mechanics often focus on these simple bolt-on parts, such as higher-flowing exhausts, free-flow filters, bigger throttle bodies, and the like, for good reason: Their benefits are easy to understand and installation is simple. Camshafts are another area where Mustang owners can prompt a significant increase in engine torque and horsepower. The problem for many beginners is that the camshaft option can be downright scary. Aside from the installation demands (which aren't complicated with a set of good instructions), there's the question of which cam to buy and deciphering those cryptic numbers and terms on cam spec charts, so we'll attempt to clear things up for you.

Our focus is on cam upgrades for '89-'95 5.0L Mustangs. As you're probably aware, these models featured the hydraulic roller cam and roller lifters in conjunction with the mass airflow metering system. The '85-'88 5.0Ls also featured roller cams and lifters, but used a speed-density control system to measure air intake. As a result, cam profiles manufactured for mass air applications aren't necessarily compatible with the '85-'88 roller engines that use speed density.

First, let's look at the basics. A camshaft sits high in the engine block between the cylinder banks and is rotated via the timing chain that's also connected to the crankshaft (which turns the cam). Cams on the '89-'95 V-8 Mustangs are made from steel, instead of iron, which is what the earlier, flat-tappet Mustangs cams were made from. The cam spins on bearings seated in the blocks and features eccentric lobes along the shaft-one for each intake and exhaust valve tappet or lifter. As the cam rotates in unison with the crankshaft, the lobes lift the hydraulic roller tappets seated in the cylinder heads. As the tappet rolls up on the cam lobe, it pushes the pushrod upward against the bottom of the short end of the rocker arm. The rocker arm pivots on a stud and effectively multiplies this lift by a ratio of 1.6:1 on the other side of the arm in stock engines. In other words, one unit of lift on one side of the arm translates to 1.6 times the unit on the other side. The long side of the rocker arm pushes down on the intake and exhaust valves, pushing them into the combustion chamber so that a fresh air/fuel mixture can be drawn into the cylinder on the intake stroke and burned exhaust gases can be expelled on the exhaust stroke. It seems like pretty simple stuff, but as you may expect, things can get complicated.

The camshaft determines the amount of air/fuel and exhaust that goes in and out of the combustion chamber, how it goes in and out, and when it occurs. Changes to these variables (flow, quantity, and timing) can significantly change the torque and horsepower output and rpm powerband (where the most power is created) of an engine. Thus, engine power-and when that power occurs-can be changed, depending on the type of cam you install in the engine. Therefore, power from a cam is delivered in terms of lift (how much the valves open up), duration (how long the valves are open), and air/fuel and exhaust gas speed (how quickly the valves open and where, as determined by the cam lobe profile).