/6 Matt, looks to me as if you haven't heard "all" about them; your guess is a perfect 180° off. The "bent" runner is supposed to be that way. It was made that way on the EB-welded aluminum 1bbl and 2bbl intakes on purpose to fix a longstanding tendency of the slant-6 to run rich on certain cylinders due to complex vagaries of flow out of the plenum and into the runners. Engines equipped with the EB-welded manifold show better cylinder-to-cylinder mixture balance. You don't have to believe me on that, you can read about it in
the apposite SAE paper about these manifolds, and in "A History of Chrysler Corporation's Slant-Six Engine" by W.L. Weertman.
These manifolds work well
if they're not floor-cracked,
if the welds aren't porous, and
if the mount plane is nice and flat. The floor cracks are easy to understandthin aluminum isn't as heat-tolerant as thick aluminum or thick cast iron, so over the years the extreme thermal cycling in the hotbox area of the floor of the plenum can cause cracks. Fortunately the cracks are also easy to spot by careful inspection after cleaning.
The mount plane is also easy to true up if necessary, same as you'd do with any intake manifold.
The weld bead porosity isn't as big an issue as it is sometimes made out to be. Those weld beads look ugly, but the pockets and holes don't go very deep; they're generally just on the surface. There were relatively few porous ones, and most of those were melted down as scrap metal many years ago. Even in the unlikely event you happen to find a porous one, it's not difficult to fix/prevent vacuum leakage. There are several techniques; some of them are described and pictured
here. Another good method is to have the manifold powder-coated. Or you can clean the manifold thoroughly, put it in the oven til it's up to 200 degrees or so, remove it and quickly put a bead of a good aluminum RTV (I like
Valco 71195 applied with the help of their clever
Tube Grip) to the entire weld bead, smooth the RTV firmly into the weld bead surface with a finger (don't burn yourself), then refrigerate the intake. As the metal cools it will draw the RTV into the air pockets on the surface of the weld bead. If you want to be super extra sure about it, powder coat it ("aluminum" powder coat looks great then do the RTV thing once you have it back from Leanne (or whichever other powder coater you might inexplicably choose instead).
