Assessing The Condition
Upon arrival, Keith Wilson called and from our description, he was expecting something much worse than what arrived. “Yours is one of the better ones we’ve seen. This will be easy. Some of the stuff we get is really pretty nasty,” said Wilson.
All production small-block aluminum manifolds came with this stamped steel heat deflector (left) riveted into place on the lifter valley side of the manifold. This prevents hot oil from baking onto the heat crossover passage. This porosity damage (right) was probably the worst damage to our intake but the Wilson people passed it off as just another day behind the TIG torch. Their repair was seamless.
We were encouraged by that, but were still anxious to see what could be done with our corroded example of 1967 intake manifold technology. In order to completely clean the intake, Wilson carefully removed the four small rivets that retain the heat shield. One advantage to this is that we were able to verify the manifold’s date code as appropriate for our 1967 engine. This was reinforced by the “3917610” casting number on the manifold’s top side, which our research indicated was originally intended for the Z28 engines for 1967 and 1968.
Our manifold had been mistreated where the original ignition coil was mounted and that area was going to need some surgery. The area where most Chevrolet aluminum manifolds corrode is the shelf for the thermostat. This is where two dissimilar metals are located, which tends to accelerate the electrolysis process. The softer aluminum gives up electrons, creating pitting and corrosion. We’ve seen manifolds where this shelf has all but disappeared, making a repair difficult.