I am rebuilding my motor and going with a 383 and I am just wondering about re-using my lightweight flywheel or my heavier stock flywheel - the difference in weight is 7 lbs - is that going to make any power difference or is it just going to be a difference in the way the car revs up? I was thinking of going back to the stocker for driveability at lower speed. Thanks.

 

A heavier flywheel shows up as less power to the rear wheels on a dyno, since the engine has to use part of its power to bring the rotating mass up to speed. But in a drag race application, when you rev the engine at the line, the heavier flywheel stores more energy so more power is available for the launch.

 

What other things on a car store more energy even though they show up as power losses on a dyno?

 

Anything that can be rotated to high speed before your launch. Pretty much stops at the flexplate/torque converter on an automatic, and the flywheel/clutch on a manual.

Anything that is at rest - tranny rotating elements, driveshaft, differential, rear axles, brake rotors, wheels and tires - will absorb the energy needed to accelerate it from rest to its maximum RPM, reducing the power available at the contact patch.