Richard Holdener
March 1, 2008
Bolting on a set of Three-Valve cams can be a rewarding experience-just remember to order them in time for your dyno test.

This test had all the makings of a legendary tech story, the kind people talk about for years to come. You know how we do it here at MM&FF-it's balls to the wall or nothing at all. If others run a test on a single cam combination, we grab every cam available and don't leave the dyno until every last horsepower is present and accounted for.

Obviously, it takes considerable time, energy, and planning to pull off such tremendous feats of technical wizardry, but our readers deserve nothing but the best, right? Having already applied this all-or-nothing program to the 4.6L Two-Valve motors, we decided it was high time the latest mod motor got the same treatment. Just imagine how helpful having a direct back-to-back test on all the available Comp cams would be when it comes time to choose the proper sticks for your mod motor? You'd be able to determine not only how much extra peak power was available, but if that extra power came with any type of trade-off. You could see how much each successive jump in cam timing altered not only where the motor made peak power, but also which one offered the most peak and average torque.

The XE253H-114 cams designed for the 4.6L Three-Valve motors offered a 0.480/0.470 lift split, a 214/227 duration split, and a 114-degree lobe-separation angle.

The battery of tests run on all of the available cams offered by Comp Cams for the 4.6L Three-Valve motor would provide a wealth of data, right? Your author thought so too, but here's why you won't be reading about all that wonderful data. After searching through every last page of my big book of excuses, I came up empty, zilch, nothing, nada. On the surface, it might seem possible that there's the slightest chance I might be to blame here. Apparently, you have to not only actually order all of the cams needed for said test, but do so in such a manner that they actually arrive in time for the test session.

As it turned out, this was a lot of information for one idiotic tech editor to remember. I had everything else covered. The test motor was assembled, complete, and ready to run-ditto for the FAST fuel injection and even the new Bassani exhaust including headers; mufflers; and a trick, new collector design. Also at the ready (if necessary) was my own intake manifold, the necessary Rockett Brand test fuel, and even a case of Lucas 5W-30 synthetic oil. I had all the bases covered for the mega-mod-motor cam test, except for the actual cams.

The test motor featured a 5.0L stroker short-block from Coast High Performance topped off with a set of ported Three-Valve heads. This type of motor certainly deserved something more than the stock cam profiles.

Well, truth be told, I wasn't a complete screw-up, as I already had the stock cams (big deal) and (saving me from those lengthy lines in the unemployment office) even a set of Comp Xtreme Energy XE253H grinds ready and waiting. What started out as the granddaddy of all Three-Valve modular cam shootouts turned out to be just another single-grind cam test.

While the step down in the scope of the cam comparison was hard to swallow, it didn't mean there wasn't good data to be had from the direct back-to-back test. After all, even the mildest of the Xtreme Energy offerings had plenty to offer, including a sizable jump in lift and duration over the factory grinds, worry-free installation (no piston-to-valve issues), and the knowledge that anything that comes from Comp is a quality product ready to offer years of trouble-free service. The Comp XE253H-114 cams (PN 127100) cams offered dual-pattern lift and duration specs. The lift values checked in at 0.480 on the intake and 0.470 on the exhaust. The duration was skewed in the opposite direction, with the intake offering 214 degrees (measured at 0.050) and the exhaust lobes checking in at 227 degrees. Given the cam grind number, it's not surprising that the Xtreme Energy cams offered a lobe separation angle of 114 degrees.

Since our 5.0L stroker test motor was previously set up for the larger XE261H cams, there was more than enough piston-to-valve clearance for these smaller grinds. Our ported heads also featured the necessary valvespring upgrade, as Comp recommended PN 26113-24 springs and PN 724-24 or 792-24 retainers for use with these cam profiles.