"When I first saw this little Magnuson blower on my small-block I thought it was just a toy. Then I climbed behind the wheel, nailed the throttle, and man, this thing's power flat-out scares me." That statement from renowned rearend and hot-rod builder Frank Currie perhaps best describes the experience one feels with Magnuson's new 122-HH supercharger. The system produces hordes of tire-frying torque and very docile low-speed operation and is compactly packaged. We're talking almost 600 lb-ft at 3,900 rpm from a carbureted 400ci small-block! From the moment we heard about this, we knew we had to check it out firsthand.
The 122-HH is a newly designed unit that's vastly improved over the Classic-112 Supercharger. Unlike an older-style, traditional blower that pulls air from the top to the bottom, the Magnuson unit is axial flow. This means the air moves from the back to a front discharge. If you don't already know, the Magnuson unit is based on an Eaton supercharger that is essentially a hybrid Roots-style pump. However, the Eaton/Magnuson style has one major difference: Each of the two rotors has been twisted even more, forming a higher helix, which adds more inlet timing to the supercharger. These two counterrotating rotors have three lobes each, which intermesh during engine operation. The new 122-HH takes this principle a step further with high-helix rotors (hence the HH). This provides an improved flow that reduces pressure variations, for a smoother discharge of air and less noise during operation.
At the rear of the 122-HH supercharger is an internal bypass valve (or unloader valve) to reduce mechanical power losses at cruise speed (when vacuum is high) and increase economy. This allows a negligible net power loss of about 11/43 hp. Additionally, the hybrid design of the 122-HH carbureted supercharger provides an 85- to 90-percent volumetric efficiency. This is made possible because the 122-HH's uniquely shaped rotors produce better sealing efficiencies. In essence, as rpm increases, air speed is raised for better volumetric efficiency.
While at the Magnuson's test facility we collected dyno data on the new package. The test engine was fitted with a Holley 850-cfm HP blower carb, a Comp Cams solid-roller camshaft (see engine specs for complete details), and a set of Trick Flow 215 heads. At just 2,000 rpm the pressure gauge was already showing 5 psi of boost and yielded an amazing 556 lb-ft of torque. Higher up the rpm scale, the power peaked at 598 lb-ft of torque at 3,900 rpm and largely continued in the 500 range until 6,100 rpm and nearly 600 hp! Sounds like a winning combination to gain lots of power.
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Critical to the installation of any supercharger is an improved fuel system. Magnuson recommends increasing fuel pumps and fuel line capacity by approximately 50 percent over nonsupercharged engines. If not, considerable engine carnage will result from insufficient fuel delivery. Remember to check the size of fuel pick-up in the tank-and all fuel lines too. | 
The 122-HH is designed to utilize factory frontend accessory-drive components (alternator and power steering pumps) and brackets in their stock locations (currently available for long water pumps only). Upgrades include March pulleys and bracketry, Billet Specialties components, and Vintage A/C-drive systems. |