Now, it may appear that Joe was speaking a foreign language, but what he means by a four pound crank pulley is often what Mustang tuners refer to as a larger diameter supercharger drive pulley that is mounted to the crankshaft to provide greater blower overdrive and four more pounds of boost without changing the supercharger's driven pulley, which is on top. This results in increased supercharger speeds in relation to the crankshaft, and more boost earlier in the engine's operating range. However, it should be noted that it seriously overdrives the supercharger beyond the factory-recommended shaft speed, but, what the heck, if all the cool kids are doing it, why can't we?
So with Joe's recommendation made, we turned to Metco Motorsports, which specializes in crankshaft pulleys for the '03-'04 Cobra. Metco's supercharger crankshaft pulley kit is modular in design and allows you to change the pulley size based on the boost increase you want. For instance, if you wanted two more pounds of boost, you'd simply use a two pound pulley ring, four more pounds of boost, you'd add the four pound ring, and for six more pounds of boost ... well, you get the picture. The best part about the Metco kit is how the design of the pulley does away with the factory 'cage setup that is bulkier and takes more horsepower to operate. By switching over to the easy-to-install Metco setup we saved about five pounds right off the nose and added some nice bling to the underhood area as the crank pulley's hub is fabricated from billet aluminum and the interchangeable pulley rings from black-anodized billet steel. Because the supercharger drive system also drives the alternator, you will have to replace the alternator pulley with a larger one to slow it down whenever you use a four pound-or-larger crank pulley.
With our new ported Eaton installed and pulleyed up with the blingus maximus Metco components, we headed to the dyno bay at Mustang Magic and rolled our Cobra onto the Dynojet 248c, as Joe plugged in his SCT Tuner to reprogram the PCM. By pulling some timing out down low and trimming the fuel curve to match, he was able to prevent any potential detonation from the big gains in boost that we were about to see.
On our first pull, we were able to notice a louder shrill from the blower. With nothing else, we were quickly rewarded with an incredible 471 rwhp and 506 lb-ft of torque. This was with a boost increase of four pounds (as advertised by Metco) from 12 psi to 16 psi. Horsepower-wise, we were looking at a modest 18 rwhp gain, but as Lauzardo mentioned, the peak horsepower gain wasn't going to be strong because at around 5,000 rpm, the stock Eaton started to lose in boost, going back down to about 12 psi all the way to redline. The primary issue here is the combination of the restrictive factory throttle body and inlet, as well as excessive supercharger speed, caused by internal turbulence that capitates the air. Much of the gains were throughout the bottom part of the power curve starting at a mere 2,500 rpm as we were seeing the gains from idle to the 4,000 rpm boost peak with a peak torque gain of 53 lb-ft over our previous best. With a relatively safe 11.8:1 air-fuel ratio at peak horsepower, we left it alone as the use of pump gas was important to us.
The only way to find out how extra horsepower translates in the real world was to head down to Old Bridge Township Raceway Park and line our car up on the dragstrip. With an aggressive slip-clutch launch at 2,250 rpm on the 17-inch Nitto Drag Radials, we were able to better our previous best of 11.925 at 118.92 with a new best of 11.59/122.5 mph. Granted, the track temperature was about 25 degrees Fahrenheit cooler, but there was no arguing how the car responded with its newfound power.
The intake manifold mounting...
The intake manifold mounting flange is cleaned with brake cleaner. We then installed the factory metal gasket dry. Make sure the gasket is properly aligned with the dowel pins as it will make the installation much easier.
Using a 10mm socket, we tightened...
Using a 10mm socket, we tightened all ten bolts to spec with our specially calibrated torque wrench (two flicks of the wrist until your pinky starts to slide off).
We then transferred the Mustang...
We then transferred the Mustang Magic 3.0 pulley from our stock blower and installed it into our ported Eaton with Metco's pulley tool. This easy-to-use tool is essential to properly facilitate the installation or removal of the Eaton's press-on supercharger pulley without damage.
With the front drive reassembled,...
With the front drive reassembled, we decided to add some beef to our drive system by installing Metco's innovative idler pulley reinforcement bracket, which acts like a girdle to tie in the three mounting bolts for increased support and less flex at the attachment points. It also prevents the idler arm itself from flexing by providing a backing surface for it to ride on should it bend more than 0.030-inch away from the motor. With the included hardware, it only takes a minute to install.
The next part of the equation...
The next part of the equation was to remove the factory supercharger drive pulley with the included 14mm internal hex crank pulley socket. Keep in mind this bolt needs to be turned clockwise to undo the reverse threads.
Alongside the Ford pulley...
Alongside the Ford pulley and 'cage assembly, the Metco units look so much more refined. Aside from shedding about five pounds of weight off the nose, the Metco kit bolts right onto the factory harmonic damper and uses an interchangeable pulley system. We opted for the four-pound pulley to increase boost pressure the like amount. The rest of the hardware bolts right up and provides sturdy mounting points for the wiring harness and other things that were removed with the factory pulley and 'cage.