Here are some results I have found on a slant six (I know not a race engine) but they are interesting. All tests were on a Mustang Chassis Dyno.


With the 1-bbl (1920 Holley) carburetor:
factory OEM filter in factory air cleaner housing
Max Torque : 132.558lb-ft
Max Horsepower: 83.177hp
Avg Torque : 122.779lb-ft
Avg Horsepower: 76.279hp


K&N filter in factory air cleaner housing
Max Torque : 134.171lb-ft
Max Horsepower: 83.767hp
Avg Torque : 122.590lb-ft
Avg Horsepower: 79.365hp

Improvement over baseline
Max Torque: 1.583lb-ft
Max Horsepower: 0.590hp
Avg Torque: (-0.189)lb-ft
Avg Horsepower: 3.086hp


Baseplate only (no filter)
Max Torque : 132.827lb-ft
Max Horsepower: 84.484hp
Avg Torque : 122.213lb-ft
Avg Horsepower: 79.088hp

Improvement over baseline
Max Torque: 0.269b-ft
Max Horsepower: 1.307hp
Avg Torque: (-0.566)lb-ft
Avg Horsepower: 2.809hp

I will get the data together for the 2-bbl and the 4-bbl carbs/filters and post it as well.

Chris