if the wire or boot leaks slightly it could short to ground through the Alum
Well, my Firebird uses the same type aluminum wire protectors. And if you had damaged wires
that were conducting to the aluminum, obviously they should be replaced anyway. Also,
unless the aluminum is in contact with the head or headers, there would be no short to ground. I'd say
there is a much better chance of wires being damaged by the header heat, than there being
a short to ground. Good way to check for cracked plug wires is to observe them while the car
in running, in the dark.
Also, ceramic coated headers (coated on the inside and out) is another helpful method of keeping
the wires cooler.
Just saw a recent post where the guy had those sock type insulators, and one caught on fire,
which is a much more serious situation, with the potential for major damage!