there for two different applications...
one is to bring air in, for a specific purpose ie.. to cool an intercooler, or for ram air...
wheras the other is designed to evacuate heat rapidly...
the second one "cowl hood" is popular among musclecar tuners becuase of the massive heat created by running high compression 8 cylinders..
the heat needs to be evacuated or the engine can overheat...
a trick i learned from some mustang buddies... to make a spacer, to lift your hood at the hinge at the back of the hood... so when the hood is closed the front is closed, but the back of the hood is raised an inch or so allowing a rather large gap for all the XS heat to escape....
good idea, but A) looks kinda goofy...B)it rains right in...
so i got to lookin at the twin wall that ford used on the capri and i thought hey instead of moving the hood up lets move the firewall down..