I'm no mechanic.... but this can't be normal

[johnjmurray]

I tend to agree with Kylant, I assume those manifolds are cast from grey iron which is very prone to corrosion. But I'm open to other thoughts on this matter.

[Andrew]

my manifolds have been on "death row" for 7yrs if rust is a sign of failure....... i think ur fine

[SquamInboards]

I can't recall the last 351 I saw over 3 or 4 years old without some rust on the manifolds... how much rust are we talking about?

[tadelfio]

Ditto on the manifolds. If the gaskets aren't leaking then leave them alone! They are very expensive to replace if the manifold breaks. If you have to drill out the bolts, then the manifolds are probably pretty rusted and more than likely will break.