15-20 additional horsepower.
   Another easy step to increasing power output is to optimize the spark output. The TPI Specialties SuperFlow dyno showed that installation of Bosch Platinum +4 spark plugs and TPIS spiral-wound plug wires was good for an increase of seven horsepower.
   The increases delivered by the air filter and ignition upgrades are impressive for simple bolt-ons, but it's no secret that internal modifications pay larger dividends. So Cottrell's next step was to pull the engine apart and make a few changes. Although he did a complete rebuild, the bulk of the power increases were derived from a camshaft change and cylinder head modifications. (Since the engine was scheduled to develop an intimate relationship with the dyno, Cottrell installed a Lunati forged steel crankshaft and forged 6.300" long connecting rods.)
   In its final form, the test engine maintained stock bore and stroke dimensions and was fitted with ported cylinder heads and a TPIS ZL11 camshaft that sports intake