Modular Motor Shootout - Three is the New Four

Kenne Bell's charge cooler... 

   

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Kenne Bell's charge cooler is built around the efficient Mustang Cobra heat exchangers. The plumbing and reservoir tank are KB parts; this one features a reservoir with a large opening for adding ice at the dragstrip.

Being careful to add mechanical strength while not changing the Three-Valve's power potential, the engine was specifically set up to retain stock compression, valve sizes, cams, and oiling. The SHM short-block was built using an iron block, Manley rods and pistons, a Cobra crank, ARP bolts, and Inconel exhaust valves from Manley to round out the tough stuff. Stock Three-Valve heads with a stock valvetrain, except the valve material, were retained. The combination is what SHM offers those requiring 850 hp worth of longevity. As an interesting aside, Adam reports the iron-blocked engine is mechanically quieter than he expected.

Externally, the engine remains stock. The exhaust for all testing was stock cast-iron manifolds, gutted stock cats, and a quiet aftermarket axle-back muffler section. We were disappointed by the gutted cats, and the Cobra we are comparing it to used stock cats, putting it at an immediate disadvantage. On the other hand, we admit the low-restriction cat section is more realistic when reaching the 600-rwhp horizon. To be even more realistic, a proper set of long-tube headers and dump tubes would make things interesting when ST Motorsports inevitably tries for all-out power production in the future

Other nonstock items included a Cobra flywheel and a custom ceramic clutch from Clutchmasters. Adam was positive on the clutch, saying it bites hard with no slip. We don't think these parts influenced the Dynojet readings much.

While it has no affect on the dyno tests, it is interesting to consider the weight ramifications of the blower and iron short-block. Adam figures the blower added 100 pounds, the block 80 pounds, and his rollbar 20 pounds to his already 3,850-pound GT, making it heavier than the Cobra.

Getting air into the naturally... 

   

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Getting air into the naturally aspirated side of the supercharger is a major part of building big power with any blower system. The KB Cool-Air Intake is used, which fits a 9-inch conical air filter, 90mm mass air meter, required hoses, and tubing-to-duct air to the throttle body.

Reviewing our March '03 Cobra test, we see the basic engine was mechanically stout due to its factory-installed forged pistons and rods, excellent crankshaft, and free-flowing Four-Valve cylinder heads. As the engine and fuel system were built by Ford for blower power, Kenne Bell was able to substitute a supercharger atop the Cobra manifold and charge cooler, with the rest of the job orbiting around tuning issues and supporting hardware. KB's in-house tuner Ken Christely concentrated on sorting out Ford's fuel pump control strategy and tuning tables, along with getting air into the supercharger. In the end, the major hardware changes were a large conical air filter and plumbing-KB calls this a Cool-Air Intake-a fuel controller, and Boost-A-Pump to manage the stock fuel pumps.

It's amazing how stock the Cobra engine was. Even when reaching well over 600 rwhp, the stock 90mm mass air meter, throttle body, intake and exhaust manifolds, engine, and functioning catalytic converters were in place. All testing was done with 103-octane unleaded race gas, except for the Hail Mary run when two gallons of 116-octane leaded were added for extra insurance. The air filter was removed, but the Cobra was still easily ready for 600 rwhp.

Important steps in the Cobra's power build are listed below.

Adam detonated and glazed...        read full caption Adam detonated and glazed more than $1,000 worth of spark plugs while tuning his Three-Valve to 700 rwhp. He tried all sorts of gaps and other tricks, but in the end reverted to near-stock gaps and a KB Boost-A-Spark ignition booster. The shiny glaze on this plug is mute testimony to how it is inside a highly boosted cylinder when the air/fuel ratio wanders into forbidden territory.

It doesn't take an advanced...        read full caption It doesn't take an advanced degree to see why the stock 2x52mm throttle body doesn't flow as much air as the 2x60mm V-10 throttle body next to it. Hardly as visible, but even more important at elevated power levels, is the S197 fuel system. It uses 51/416-inch fuel lines, and requires upgrading to support 600 and 700 hp engines.

Adam is a confirmed S197 Mustang...        read full caption Adam is a confirmed S197 Mustang enthusiast. He figures he is the first to breach the 700 rwhp wall with his GT, making him one happy camper.