Actually a good cast manifold will far outlast a mild steel exhaust system.
The header will eventually rust from the inside out (unless hot coated),
or "eventually" crack from metal fatigue somewhere from the vibrations
caused by the running engine. And even if it doesn't a typical header will
be much more difficult to keep sealed between the flange and the head, and
usually between the outlet flange (if it has one) and exhaust pipe. If
your going for longevity and ease of maintenance, go with a good cast
manifold. If you want a little performance boost and are willing to put up
with the slight aggravations just mentioned, go with the header -
Barry Schwartz (San Diego) bschwart@pacbell.net
72 PI, V6 Spitfire (daily driver)
70 GT6+ (when I don't drive the Spit)
70 Spitfire (long term project)
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