"Lump ports" raise the bottom of the intake ports to change the angle of the gas flow as it approaches the tulip area of the back of the intake valve. It's a trick to improve the volumetric efficiency of the head, and it actually makes the port smaller. The velocity of the gases passing through the restricted port increase, which supposedly improves the "ram effect" of the intake charge as it fills the cylinder.
The problem is- - - -it only works with a very radical camshaft profile, and only at wide open throttle, high RPM operation- - - - -like a huge number of other race-type modifications people do, whose vehicles never get near a round track, or even a drag strip. They give up lots of low end torque and gas mileage to be able to brag about the cam that causes a lumpy idle and cylinder head modifications they'll never be able to make use of on the street without attracting Deputy Dawg and his speeding ticket book. I've proved those assertions to the students in the auto mechanics classes I taught over 30-somthing years, repeatedly, with more dyno runs than I can count.
Other than that, those modifications are great! (Where's that "sarcasm" emoji when we really need it?)
Jerry
