When most Pontiac fans think of blown GTOs, images from the mid '60s of GTO match racers driven by Don Gay, Dick Jesse, Arnie Beswick, and others are likely to come to mind. However, the world's a different place now, a better place where superchargers and street driving go hand in hand and heavy GMC 6-71 huffers are replaced by compact yet capable Eaton blowers which fit underhood and are invisible to prying eyes.

Today, Magnuson Products leads the charge (literally) in the supercharged GTO arena with its brand new MagnaCharger kit for the '04 GTO. Completely emissions-legal in all 50 states and happy to sip 91-octane unleaded, we watched as the stock GTO output rose from 262 hp at 5,250 rpm and 286.2 lb-ft at 2,750 rpm to an amazing 386.7 hp at 5,500 rpm and 420.2 lb-ft at 3,250 rpm on Magnuson's in-house Mustang chassis dyno.

Though our Arrowhead Performance test car was stone stock for the baseline chassis dyno test, the exhaust system had been replaced by a Spintech dual-cat, side-exit off-road system by the time the blower was installed (see our September '04 issue for the Spintech story, "True Duals for the New Goat"). Without the free-flowing exhaust, we'd bet the power numbers would be down a small amount, but not enough to make a huge impact on rapid forward mobility. Remember, the factory exhaust manifolds were still in place.

A quick test drive in our huffed test car yielded much improved acceleration in every gear over the GTO's already impressive capabilities and a satisfying blower whine at medium throttle that mutated into a banshee wail when the pedal hit the floor. The beauty part is how the blower is nearly silent until your right foot calls it out to play. Then its 6 pounds of boost require extra care to prevent tire spin at throttle openings the stock GTO can normally handle without any risk of lost traction. Are we complaining? No way. However, slicks will be the order of the day at the strip. On the freeway, the extra torque makes the 5.7 feel like it's grown an extra liter of displacement and you can pass just about anything you're likely to encounter.

We pulled some strings to bring you this exclusive behind-the-scenes look at how Magnuson adapted its famed Eaton-sourced lung to the new Goat's 5.7L Gen III mill.


Magnuson designs, develops, and produces bolt-on supercharger kits for a wide variety of late-model applications. Every one of these packages goes through a lengthy prototyping and fabrication process before production-ready units hit the streets. The new GTO is no exception. While Magnuson offers several MagnaCharger kits for vehicles equipped with the General Motors Gen III engine, the unique packaging of the 5.7L LS1 powerhouse in the Holden Monaro-sourced GTO required some adaptation. Here's a rundown of how Magnuson's team overcame the hurdles.


Most enthusiasts take a quick glance at the MagnaCharger and assume it's a miniature version of the venerable GMC 71-series supercharger. Not so! While the iconic GMC diesel huffer set the pace, MagnaChargers are dry flow units (gasoline is injected at the ports) and feature integrated intercoolers. Best of all, MagnaChargers are emissions legal for late-model muscle machinery and are priced at $5,995 in natural aluminum finish or $6,995 for the sexy polished job shown here. Let's look at what makes the MagnaCharger tick. Remember, you ordinarily won't see this stuff, as all MagnaCharger kits come fully assembled and ready for easy installation.


By now every GTO hobbyist knows that the '04 GTO is powered by the rompin', stompin' LS1 motor. However, it isn't just a quick slam dunk and g'day using an existing F-car (Camaro/Firebird) or Y-car (Corvette) mill. Rather the LS1 used in the Holden Monaro CV-8, er, um, Pontiac GTO, has many specific features to match the chassis architecture of its Aussie host.


The MagnaCharger people claim their kits generally add 20 rear-wheel hp per pound of boost. Proving the point, they strapped the Dan Long-owned Arrowhead Performance GTO to the Mustang chassis dyno and delivered an additional 124.7 hp and 134 lb-ft of torque. Yes, a Spintech off-road, side-exit exhaust found its way into the mix before blower testing, but even with a stock GTO exhaust system, the MagnaCharger kit is sure to put any GTO over the top. Lighter F- and Y-cars won't be a problem...unless they too are MagnaCharger-equipped.

After observing Dan Long's Spintech, MagnaCharger-equipped GTO on the Mustang chassis dyno, another MagnaCharger-equipped six-speed GTO was put in its place and flogged. This second GTO lacked the quasi-legal dual-cat Spintech H-pipe and side-exit exhaust. Instead, it was fitted with an aftermarket true 50-state-legal, stainless steel, dual-outlet catback exhaust system from another company. The best peak power level generated in two back-to-back dyno pulls was within 10 hp and 10 lb-ft of the first GTO test car. After this demonstration, any concerns that the first GTO's gain was a fluke were put to rest.

Arrowhead Performance
7400 W Arrowhead Clubhouse Dr.
Suite 1013, Dept. HPP
AZ  85308
Spintech Performance Mufflers
4768 Felspar St., Dept. HPP
CA  92509
Magnuson Products Inc.
3172 Bunsen Ave., Dept. SC
CA  93003