BTW, for what is may be worth... I ran a spreadsheet on the energy absorbed by a lighter versus heavier piston/rod assembly; i.e., I looked at just the bobweight change spinning around the crank, and the associated lighter weight of the crank counterweights.
With a bobweight drop from 2326 grams to 1893 grams (what my son and I did for his 340 with KB pistons and SCAT rods), then revving from 3000 to 7000 RPM saves 2080 joules that can be put into accelerating the car.
This translates to roughly a 1/2 HP to 2 HP range; the exact HP loss varies with how fast the motor revs, and the RPM range, which is all gear and weight dependent when in a car (both mass AND other rotating parts). But 1 HP is a ball park range. It would drop 1/4 mile MPH by a coupla tenths for cars in the A body weight/power range. For reference, it takes around 1.5 million joules of energy to get a 3300 lb car moving at 100 MPH from a dead stop.
So this acceleration/HP improvement with lighter rods+pistons is in the range of crank scrapers, or using a standard oil pump vs HV pump, and will vary a lot on the particular parts and the exact use.
