Navigating Comp's Line of Three-Valve Camshafts
OK, not everyone has a stroker with ported heads, so Comp designed many cams for all applications. If you want milder camshafts, Comp offers a variety under the XFI camshaft lineup. The first set is nicknamed NSR (No Spring Required). They're designed for blown or naturally aspirated engines, and best of all, you don't have to change springs, thus simplifying the install (not to mention saving you money, too). There are two stages each for N/A and blown combos, for a total of four different cams designed for mild applications. Neither N/A cam requires computer retuning, and each offers great idle manners. The Stage 2 NSR does require a looser torque converter and also a minimum of 3.73 gears. The Stage 1 NSR blower cam is designed for out-of-the-box boost levels, while Stage 2 is for higher boost output, a looser torque converter, and steeper gears.
The second family of Three-Valve cams is called VSR (Valve Springs Required). If you hadn't guessed it, the VSR cams are much more aggressive than the NSR cams. We've tested VSR cams several times in MM&FF over the years, with great success. Our testing has shown as much as 40hp gains over the stock cars, on stock engines. As with the NSR group, there are two naturally aspirated grinds and two blower stages. The VSR camshafts carry the same description as above but feature a rougher idle and definitely need custom computer tuning.
The third and final family of cams for the triple-valve mod motor are the SPR camshafts, which we tested in the Stage 3 version in this story. Six versions of the camshafts exist on the shelf at Comp. The SPR line is divided into three naturally aspirated grinds and three blower grinds, all broken down into Stage 1, Stage 2, and Stage 3. The first two stages are mild enough to be used with stock engines. Stage 1 can be used on a completely stock engine, while Stage 2 has a rougher idle and calls for taller gears and a better torque converter. Stage 3 is designed for built engines with better flowing heads, more compression, and high boost (in blower applications).
Comp Cams' Web site (www.compcams.com) has more information on each cam and its specific applications. Be sure to check it out to see which XFI camshaft is right for your Three-Valve engine.
Enabling the cams to move is a fairly simple system using oil. The computer sends a reading to a sensor, which opens a solenoid and floods the cam phaser's control chamber. The oil enters through the hole in the picture on the top. | 
The cam bolt shown here has a hole in the middle, allowing oil to flow through it. It secures the cam sprocket to the camshaft using a 30 lb-ft setting on the torque wrench. Then the bolt is turned 90 degrees, since it's a torque-to-yield bolt. Don't reuse cam bolts once they've been tightened down. | 
The oil fills these chambers and forces the plates to twist the cam. The initial cam timing is advanced (7 degrees for stock and 15 degrees in most Comp camshafts), so flooding the chamber will cause the cam to be retarded. The oil is leaked out, and the cam returns to its advanced position. |
Here the Cam Phaser Limiter is ready to drop into place. It prevents the cam from moving more than 20 degrees in either direction. The concept is simple--the posts sit in the cam gear control chambers and restrict the moving parts. | 
Comp offers a tool to hold the clock spring in place, so you can remove the long bolt. | 
The long bolt serves two purposes: It's one of five bolts holding on the backplate, and it acts as an attachment point for the clock spring. |
You can see the difference between the short and long bolt, which are used to hold the backplate to the sprocket. | 
The backplate bolts on easily. | 
The sprocket assembly is attached to the end of the camshaft. Amazingly, the cam is turned by a little press-in dowel on the sprocket. We couldn't believe that all that power and turning goes through a tiny dowel. JDM's Shawn Lacko told us, "I have seen the dowel twisted and broken. A lot of it was due to bad tuning or the wrong oil." |
The SPR Stage 3 camshafts we used in the naturally aspirated Saleen featured some healthy specs but was still tame enough for street use. The intake lift is listed as 0.540 inch, while the exhaust checks in to this party at 0.561 inch. Lobe separation angle is 112 degrees, giving this engine a nice-sounding idle. Duration is 242 degrees on the intake side and 250 degrees for the exhaust. The camshaft sits at 15 degrees advanced; then D'Amore Sr. retards it negative 16 degrees in the upper rpm range--bringing the total to negative 1 degree. | 
You can't argue with the combination. This Three-Valve made 401 rwhp and 379 rwtq in a street-legal package. It's quite impressive from only 298 ci, and the power goes through a 5R55S automatic transmission. | 
The best time to date has been an 11.15 at 119 mph, while running at a race weight of 3,500 pounds--including driver. A looser torque converter and a larger set of gears should equal 10-second times when sorted out. |