It is well-known that header flanges can warp, resulting in leaks. They simply aren't as strong as cast manifolds and the mounting surfaces aren't as "true" once they are torqued down to the head. Steel is simply much more deformable than cast iron. The two biggest drawbacks to using headers are increased underhood heat and the tendency to develop leaks. Well-designed headers with thick cylinder head mounting flanges that have machined head sealing surfaces will have less of a tendency to leak, but it is always a possibility. The main thing is not to overtorque those header to cylinder head bolts to prevent deformation of the header's cylinder head sealing surface. Even so, it still isn't uncommon to eventually develop leaks, requiring removal and replacement of the gasket.
Just ask anyone that has headers on a small block chevy. Do some research before you criticize someone for not knowing what the hell they are talking about.
Just ask anyone that has headers on a small block chevy. Do some research before you criticize someone for not knowing what the hell they are talking about.
