NOS F-Head Exhaust Manifold Question

w30bob · Post by **w30bob** » Tue Oct 31, 2017 7:27 am

Hi Guys,

I keep seeing supposedly NOS exhaust manifolds out there that have these 4 strange bosses cast into them (circled in yellow). These aren't locations where the cast iron is poured into the mold, they're purposely added threaded bosses. The manifold on my jeep (and most I've seen in real life) doesn't have these bosses..........so why are they there? Was there a heat shield or something else that bolted to the manifold added later in civilian life that needed these bosses? Just wondering what the history....or story is behind these.

thanks,
bob

mdainsd · Post by **mdainsd** » Tue Oct 31, 2017 9:28 am

Not knowing for sure but those bosses look a lot like provisions for A.I.R. (Air Injection Reaction), a smog control system.