Complex sentence: "Flooring" the accelerator peddle would cause the engine speed to flare (even though there is no automatic downshift and no torque converter lockup to disengage), but as the car would accelerate, RPM would further climb by a relatively small amount.
Split into simpler sentences: Flooring the accelerator peddle would cause the engine speed to flare (even though there is no automatic downshift and no torque converter lockup to disengage). As the car would accelerate, RPM would further climb by a relatively small amount.