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4.6L Two-Valve Stroker Motor Build - Two Can Do
Here Is What You Can Expect From A TFS-Headed, Nitrous-Injected, 4.6L Two-Valve Stroker Motor.
Naturally, the build up also included new rings and bearings, along with Fel Pro (MLS) head gaskets and a new factory oil pump. When reusing components such as the timing chains, guides and gears, make sure they are still in good condition. We reused all of the components from our donor motor (we saved yet another 4.6L from the boneyard-this time a PI '00 version).
With our stroker short-block assembled and ready for action, it was time to upgrade our power producers. You may remember we installed a set of TEA-ported PI heads, a pair of Comp XE274H cams and the PI induction system on this engine in the Nov. '10 issue. These were (excuse the pun) head and shoulders better than the factory non-PI components they replaced, but we wanted more for our stroker. To that end, we installed new Track Heat 4.6L Two-Valve heads from Trick Flow Specialties.
Even in as-cast form, the Track Heat heads offered more flow than the ported PI heads. Credit the revised port design, valve locations, and use of a 1.84/1.45-inch valve combination. Production of the overhead cam cylinder head was difficult, so we have to give credit to TFS for stepping up to the challenge. The flow rate of the new heads immediately bridged the gap between the production Two- and Four-Valve motors. Toss in some porting from Total Engine Airflow and you have the makings of a serious set of heads. In fact, the only thing holding these babies back from eclipsing the Four-Valve heads is the available bore size. Our 0.030-over motor was not sized to maximize the flow potential of the heads, but stick these on a big-bore mod motor and you're looking at near 300 cfm.
With head flow now in abundance, we decided on a set of cams and an intake manifold. Since our stroker was destined to run sans artificial aspiration, we went not only with high compression, but also with aggressive cam profiles. The XE278AH cams combined 0.550 lift (both intake and exhaust) with a healthy 242/246-degree duration split and a lobe separation angle of 113 degrees. These cams will sacrifice low-rpm power compared to some of the other milder grinds, but they offer plenty of power on the big end. Besides, our additional compression and displacement more than made up for the aggressive cam timing.
Working with the cams and Track Heat heads was another performance upgrade from Trick Flow Specialties. The Track Heat intake manifold was offered in a number of different color and throttle body combinations, but we opted for the standard single-blade throttle body with the black finish. Though less of an issue on our engine dyno, the Track Heat intake even came equipped with the required air intake system designed to connect the throttle body to the factory (or aftermarket) MAF assembly. To ensure adequate airflow, the Track heat was fed by a 75mm Accufab throttle body. A decided step up the performance ladder from the factory PI intake, the Track Heat manifold was the final element in our three-tiered approach to improving the power output of the Two-Valve.
With our 5.0L stroker ready for action, we installed it on the engine dyno at Westech Performance and equipped the test motor with Kooks 13/4-inch long-tube headers (no extensions or mufflers), a Fast XFI management system and a pan full of Lucas 5W-30 oil. Not having access to our usual Meziere electric water pump for the mod motor (the author left it at his shop in Vegas), we were forced to pressure feed the motor from the dyno (like they do with jetboat motors). The factory water pump was installed but served as a simple O-ring to seal the cooling system.
After a pair of 15-minute break-in procedures, the motor was tuned using the FAST EFI system, and we were eventually rewarded with peak power numbers of 463 hp at 6,600 rpm and 430 lb-ft of torque at 5,000 rpm. Torque production exceeded 400 lb-ft from 3,800 rpm to 5,600 rpm.
For those wanting a peppier Two-Valve, we quickly installed a Zex universal EFI wet kit with 150hp jetting. Designed with a single fogger that combined and injected both fuel and nitrous before the throttle body, the Zex nitrous kit bumped the peak power output to an amazing 604 hp and 588 lb-ft of torque. Our little Two-Valve was now ready to take on some heavy-hitters, but make sure to check back with us as Evan and the boys finally allow me to let loose with the boost!
4.6l Two-Valve Stroker NA Vs. Zex Nitrous (150hp Shot)