My exhaust manifold uses 7/16" studs (and nuts) to attach the exhaust pipe - the exhaust manifold has stud threads in which the studs screw into.

In an earlier slant six exhaust manifold I had bolts were used to attach the exhaust pipe.

Was the manifold with the studs a later design manifold?

Evidently. I didn't check every year, to see what year it changed. Just jumped thru some parts manuals. 62 manual shows bolts and nuts, as does 1967. Studs are shown in the 1974 part manual.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

I have had exhaust manifold stud come out with the nut and become bolts...

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Casually looking for a Clifford hyperpak intake for cheap.

Perhaps the 'bean-counters' decision to control costs!