351W intake interchangeability through the years?

[Gary Lewis]

When installing an intake manifold, aluminum or cast iron . . . . always wipe both surfaces and both sides of the gasket with RTV at the water ports. I used the word "wipe" because you don'r want a lot, but you want enough to make a seal. You must break the surface tension of the cleaned manifold and gasket. You put on RTV and move it around until you see that it is attaching to the surface. Then you must assemble quickly. This is easier seen that explained, but I never have leakage problems do it this way.

That's a good approach. However, a lot of the problem that people have with the aluminum manifolds is not due to inadequate sealing, but electrolysis. You have two dissimilar metals that have a liquid on them, and unless that liquid has the proper corrosion inhibitors in it electrolysis will occur at the junction of the two metals. To put it simply, if the coolant isn't replaced frequently aluminum will be removed from the manifold and plated on the cast iron.

[PetesPonies]

That's a good approach. However, a lot of the problem that people have with the aluminum manifolds is not due to inadequate sealing, but electrolysis. You have two dissimilar metals that have a liquid on them, and unless that liquid has the proper corrosion inhibitors in it electrolysis will occur at the junction of the two metals. To put it simply, if the coolant isn't replaced frequently aluminum will be removed from the manifold and plated on the cast iron.

I fully understand the metallurgy happenings. But I haven't ever had one leak, down the road.. . . meaning after lots of usage. When the two objects are bolted together, there isn't iron touching aluminum.The RTV will keep the coolant from the mating surface. You may eat holes elsewhere . . :) but not at that junction. You get rusting at the water ports with iron and iron. The RTV will seal those pits, so no leakage can happen. Adding a thin layer is good assembly procedure IMO . . but I have seen people use too much, way too often :) And when it is thin, you have to be careful of it skinning too quickly. Anyway, just passing this on.