Jim Smart
November 1, 2007

Dyno-Testing Facts
McLearran Racing dyno-tested the new Classic Inlines aluminum head on Kelly's 10-second Falcon sedan drag car with a turbocharged, intercooled 273ci six and a C4 transmission. Here's what happened at IA Performance in Tucson.

Kelly's first pass on the dyno using a North American iron Ford head with log manifold yielded the following results:

Run Peak HP Peak TQ
1 283 at 4,800 rpm 416 at 2,700 rpm
2 270 at 4,800 rpm 437 at 2,575 rpm

Will says air/fuel ratio was stable at 11:1 running on E85 Ethanol fuel with a 450-cfm Holley two-barrel carburetor. The improvement in torque on the second run came from a timing retard and increase in boost. Note that horsepower fell, yet torque increased. Torque is what matters most.

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Here's what happened when the McLearrans installed the new aluminum head from Classic Inlines:

Run Peak HP Peak TQ
1 323 at 4,800 rpm 480 at 2,700 rpm
2 318 at 4,700 rpm 502 at 2,650 rpm

The common denominator is tuning and torque. Everything else remained the same except for a cylinder-head swap. The Classic Inlines aluminum head has given this 273ci stroker a broader torque curve on top of more horsepower and torque. This swap has yielded 40 hp and 64 additional lb-ft of torque. The McLearrans want to lean the mixture just a pinch to improve horsepower, in addition to 17 pounds of boost. A cam swap is also in the works. We'll keep you posted.

Other Ford-six buffs have noted even greater improvement in performance using a 500-cfm Holley, richer jetting, and ignition-timing tweaks. Much depends on camshaft profile, elevation, temperature, relative humidity, and good old-fashioned tuning know-how.

Because Winterboer has fitted his SportsRoof with a fuel-injected 273ci six-stroker, we don't know what to expect. When he puts this beast on a dyno, we'll bring you the results.

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