5.7 manifold errosion

[Bushwacker]

Originally Posted by FishStretcher

. . . I wonder if edelbrock etec 170 heads would fix this. They are aluminum and supposed to be a replacement for the vortec heads. Something I am interested in, but haven't fully researched.

Aluminum heads might actually work very well for a couple of reasons. It's improved conductivity relative to iron makes it easier to cool down hot spots. And although it has a much lower melting point than iron, the aluminum oxide that forms at high temperatures is actually a tough ceramic that tolerates very high temperatures in addition to acting as insulation. Although turbine vane alloys are nickle based, the better ones contain a significant amount of aluminum, which forms a protective oxide on the surface. The oxide will eventually spall off, exposing fresh material which then forms more aluminum oxide on the surface, so it's a self-healing process. We used to enhance it by just packing the parts in a retort full of pure aluminum powder and then cooking them at high temperature in a vacuum furnace. The aluminum would diffuse into the outer 5-10 mils of the surface and then create a very robust aluminum oxide layer when run in an engine. The same thing will happen in the exhaust ports of an aluminum head!

This oxide formation is one reason why the V-4/V-6 outboards can get away with dumping hot exhaust gas into the V of the aluminum block, but it also forms on bolt hole threads, which is why you often had to use a propane or acetylene wrench to remove the bolts from the exhaust covers on the old cross-flow motors! I'd be sure to use plenty of Never-seize on the exhaust manifold bolts!