Can anyone tell me why the intake manifold on my '55 239 looks like it is overheating in the middle ports on both sides? when I found the truck 4 years ago the original manifold had a hole about the size of a dime on the middle port of one side. After rebuilding the engine and installing a new (used, but new to me) intake, this one is discoloring really bad and has cooked the paint off both sides but only on the middle sections.

55 F100  Summerville, SC