quantifying
the power increases provided by a variety of engine modifications. As a first
step, Osucha installed a completely stock LT1 on his Superflow 901 dyno, pulled
the handle and waited for the print out. In the horsepower column, the largest
number was 293. That’s awfully close to the factory 300-hp rating and probably
would have equaled it had it not been for modifications to the exhaust system
that were required to fit the dyno cell.
Retaining the stock air/fuel and ignition calibrations,
the LT1 was next fitted with a pair of castings that had been modified by CNC
Cylinder Heads,
Inc.
With the CNC heads harboring freer flowing ports, torque rose slightly from
331 to 339 lbs./ft., but horsepower jumped to 320 - an increase of 27. A careful
read of the dyno sheet reveals something else of significance - the power peak
occurred 500 rpm higher, yet torque did not drop below the rpm level recorded
with stock heads. Typically, when the speed at which peak horsepower is increased,
low speed torque is compromised. The fact that it didn't is testimony to the
highly effective port design developed by Pete Incaudo of CNC
Free-breathing
heads aren't particularly fond of restrictions in the intake system, so in place
of the stock 48-mm throttle body, Osucha installed a TPI Specialties 52-mm version
with air foil. The swap paid off with another bump in the power curve. TPI Specialties
also offers 58mm throttle bodies, but these are best suited to 383 and larger
engines; they’re typically too large for a stock displacement LT1.
