The camshafts are from the XFI line and dubbed SPR, which stands for Springs and Phaser Mods Required. Installing the SPR Stage 1 and Stage 2 cams in stock bottom-end combinations will be useful--just be sure there are better valvesprings to handle the greater rpm and load. The SPR Stage 3 cams are designed for engines with aftermarket pistons, more compression, and heavily ported heads.
All SPR camshafts require Phaser Limiters, and cam timing is set at 15 degrees advance. As the engine climbs and the computer retards the camshaft, the same 9-degree retard (the stock adjustment) takes place, and the total camshaft timing works out to be positive 6 degrees. As mentioned earlier, the stock cam is set at 7 degrees advance, 9 degrees removed, and the total at high rpm is negative 2 degrees. With the camshafts being limited to 20 degrees of movement (in relation to the crank), there's a need to tune the computer system to account for the limited movements.
Our test subject is a car that should be familiar with regular readers--Jim D'Amore III's '06 Mustang. We've become obsessed with his naturally aspirated combination. It's easy to fall in love with this Stang because of its simplicity and effectiveness as a dragstrip stormer and street brawler. The combo is sedate, yet runs low-11s at 119 mph when the money's on the line. This envy-ridden machine consists of a JDM-built 298-inch stroker engine, which uses a 3.750-inch stroke crankshaft, Manley rods, and forged pistons (11:1 compression). The heads feature a JDM-spec port job and larger Manley intake and exhaust valves. The intake manifold remains stock but breathes easier thanks to a C&L Racer cold-air intake and a larger SCT MAF sensor. Exhaust is pretty much par for the course with Kooks long tubes, an x pipe system, and a MagnaFlow after-cat exhaust system.
Surprisingly, the stock camshafts were utilized for the better part of 2007, and they worked well with the increase in cubic inches, compression, and cylinder-head flow. "At the time we did the engine," D'Amore Sr. says, "I wasn't impressed with anything on the market. I figured we'd leave the stock cams in place until something came out." In that trim, the Saleen clone spun the DynoJet chassis dyno to a max power reading of 350 rwhp and 366 rwtq through a stock auto trans, and ran a best e.t. of 11.51 at 114.50 mph.
VCT is awesome, but its ability...
VCT is awesome, but its ability to adjust cam timing also causes an interference problem when adding larger camshafts. To combat this problem, Comp Cams released its Cam Phaser Limiter kit. It reduces the cams' movements from 60 degrees (in relation to the crank) to a mere 20 degrees.
The Stage 3 camshafts feature 0.540-inch lift on the intake and 0.561-inch lift on the exhaust. Lobe separation is listed as 112 degrees, while the duration checks in at 242 (intake) and 252 (exhaust). Because the cams are designed to make power higher in the rpm band than stock, a minimum of 3,000-stall speed in your torque converter is required, as are a minimum of 4.10 gears for full optimization. With a manual transmission, just a gear change to 4.10 or higher is needed. Likewise, the Stage 3 camshafts are designed for engines with a built short-block.
After swapping the sticks, we noticed an aggressive idle emitting from the center-exit exhaust system. The car growled, and its presence was definitely known, especially when D'Amore III rolled the car into the dyno bay. Things were about to get interesting, but first the elder D'Amore had to make provisions in the ECU before we could have fun. "I had to change the specs to prevent the computer from going into the fail-safe mode," he says. "The computer will change the cams up to 60 degrees, but I change that number in the computer to only allow up to 20 degrees. If the cams can't go as far as 60 degrees, the computer will sense it and throw the code PO340."
When the hammer was dropped, the car revved quicker and higher thanks to the new cams, and the stroker ripped off a best of 401 rwhp and 379 rwtq. The peak power picked up 51 hp, but under the curve we saw as much as 81 hp. Torque output also increased, as peak torque jumped by 13 rwtq, while we saw as much as 64 rwtq in the middle part of the torque curve.
The plate bolts on to the...
The plate bolts on to the factory cam sprocket.
On track, the story was similar, as the Mustang ran quicker and faster than ever before. The 3,500-pound Stang ripped down Englishtown's track in only 11.15 seconds at a terminal speed of 119 mph (it later went 120). That was all accomplished with the stock 5R55S transmission and a TCI 3,000-rpm stall speed torque converter. The rear gears checked in at 4.56, but a set of 4.88s is up next and should get the GT closer to the 10s--without a power adder!
Our test car might be a bit more radical than the average S197, but utilizing a better set of camshafts will benefit most Three-Valve mod motors. After all, there are 14 different grinds on the Comp Cams shelf. The company has now given you control over VCT in order to unlock the potential from your free-breathing Three-Valve combination.