Hp and E.T. 'S

Not sure exactly what you are asking about here but I will answer to see if it might help to clear things up. Obviously a 1/4 mile run will be the most accurate for a given car on a given day and a given state of tune. However, the sliding rule horsepower calculators are pretty accurate as long as you input the right info.

The calculators use wheel horsepower instead of flywheel horsepower and don't assume a percentage for parasitic driveline loss. So if you have a known 500 hp motor, figure 15-20% for power loss to likely be around 400-425 hp AT THE WHEELS.

The other factor in regards to accuracy is weight. Gotta weigh the car 'race ready' i.e.; car weight with driver, how much gas in the tank, etc.

The original muscle car motors were usually what, anywhere between 235-425 horsepower? Based on realistic driveline loss number and weight, the old drag tests from back in the day were probably pretty accurate.

The weather and track conditions will factor in to make it more finite but if you input realistic numbers into a sliding calculator, they're generally in the ballpark.

Wallace Racing 1/4mi. stats calculator.