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.

The stroker was run with a set of Bassani long-tube headers designed for an '05-up Mustang chassis.

The test motor-at least the short-block portion-came from Coast High Performance. The stock Three-Valve crank, rods, and pistons were ditched to make room for a 3.75-inch stroker crank, forged connecting rods, and forged flat-top pistons which were notched with the necessary valve reliefs. On stock pistons, only an exhaust relief is required, but our stroker motor required both intake and exhaust valve reliefs in anticipation of the larger cam profiles the author neglected to order in time.

This stroker assembly was stuffed into a freshly machined production block and topped off with a set of ported heads. We wanted to make sure the additional lift and engine speed offered by the new cam profiles would not be restricted by the head flow. As indicated, the heads were treated to a competition valve job, a valvespring and retainer upgrade, and even slightly larger intake valves. Rounding out the test motor was a stock intake and throttle body, a set of Bassani ('05-up) long-tube headers, and attending 2½-inch exhaust pipes and mufflers. We liked the sound quality of the Bassani exhaust, and having the mufflers present not only greatly reduced the noise level (compared to open exhaust), but the free-flowing combination offered no power penalty over open pipes (we tested it). What could be better than all the power without the obnoxious noise levels associated with open headers?

The Bassani headers featured 2½-inch collectors feeding 2½-inch exhaust pipes. To test whether the collectors and pipes were in any way restrictive to this test motor, we had Bassani whip us up a set of 3-inch collectors and pipes. There was no gain whatsoever from the larger collectors on this test motor.

Running the test was actually quite simple, as even cam changes are a snap on the engine dyno. The new motor was given time to break in using conventional 5W-30 oil from Lucas, but for all of the testing we switched over to the good (synthetic) stuff. During the break-in procedure, we even added some of the break-in lubricant offer by Lucas. Run with the stock cams and tuned using the FAST XFI management system, the 4.6L Three-Valve stroker produced peak numbers of 379 hp at 5,900 rpm and 405 lb-ft of torque at 4,300 rpm. It should be noted that we had no way of controlling or altering the variable cam timing offered by the Three-Valve motor. Retarding the cam timing higher in the rev range would certainly enhance the peak power production, but so too would this be the case for the Comp cams. Having tested this previously on a 4.6L Three-Valve motor on the engine dyno, retarding the cam timing by 8-9 degrees can be worth as much as 12-15 hp. Regardless, we were happy with the power and torque production of the stroker assembly and were anxious to see what the Comp cams had to offer.

Installing a set of Bassani long-tube headers can be worth some serious power. We've seen gains as high as 20 hp over stock exhaust manifolds from a properly designed long-tube header.

After back-up runs produced identical results, we got the wrenches flying and off came the valve covers, front cover, and eventually the cams themselves. It was necessary to bleed down the lifters prior to installation of the new Comp cams. This was performed slowly in the vice, as com-pressing the lifters made installation of the rockers much easier. Like the previous Two- and Four-Valve motors, the timing chains employed on the Three-Valve motors featured copper-colored links to designate the proper position on the cam and crank sprockets. We simply positioned the crank at TDC and adjusted the cams using the marks on the sprockets and chains. This should be done prior to the installation of the rockers, but make sure to install the lifters before installing the new cams. Be sure to reinstall the wheel for the crank position sensor before bolting on the front cover.

With the new Comp cams in place, our Three-Valve stroker was ready for action. After minor changes to the tune-up (to duplicate air/fuel and timing values), we were rewarded with new peak numbers of 397 hp at 6,000 rpm and 412 lb-ft of torque at 4,500 rpm. The mildest of the Xtreme Energy cams offered an extra 18 hp measured peak to peak and as much as 20 hp at 5,300 rpm. Even more impressive was the fact that the sizable gains offered past 4,000 rpm came with no penalty elsewhere in the curve.

If you check out the results of the cam comparison, even the mildest of Comp's Xtreme Energy lineup for the 4.6L Three-Valve motors offered some pretty hefty power gains. Often as not, cam changes that improve the power output by as much as 20 hp come with a loss in low-rpm torque production. Not so with this mild cam combo for the Three-Valve motor. The Comp Xtreme Energy grinds improved the power output from 4,000 rpm to 6,000 rpm and never lost any power down low. The power gains may well have been even more impressive if we had the ability to control the variable cam timing.

With no loss and plenty of extra power, even these small Comp cams would be a welcome addition to any '05-up Mustang motor. Now all we have to do is get the rest of the cams ordered so we can bring you Part 2 of the not-so-mega-modular cam test.

The test motor was assembled, complete, and ready to run- ditto for the Fast fuel injection and even the new Bassani exhaust.

What could be better than all the power without the obnoxious noise levels?