The hood may appear straight to the eye but the piano hinge underneath could be sprung. The piano hinge does not extend all the way to the end of the hood. An auto accident or an object left on top of the grille while closing the hood can damage the hinge.
It could be that the folded down edge of the hood, that bolts to the hinge, has rusted away. A common problem if the vehicle has been parked for a long time.
Separating the hood halves from the hinge can be a major undertaking especially if there is metal rust-through and/or corroded bolts.
"Adding CFM to a truck will only help at engine speeds you don't want to use." "I found there was nothing to gain beyond 400 CFM."
