:
: The extra hole in the back of the head is where
: an air tube (for the air injection system)
: connected from an air pump or the pulse
: system (gosh, can't think of the correct
: name right now). The big hole intersects
: with another hole that is drilled the full
: length of the cylinder head. Then there was
: a small hole drilled from each exhaust port
: into that long hole. The threaded hole is
: for the bolt that attaches the air tube.
:
: If the engine did not require the air injection
: system in the state it was sold then there
: was a steel cover with gasket that bolted
: over the hole.
:
: Hmmm.....wonder why they did to drill the holes
: in to the intake ports so we could use it
: for fuel injection instead??!?!? Ha ha,
: that last sentence is just a joke.
:
: Back to serious information now.... some of the
: mid 70's heads were not fully machined for
: the air injection. They only did part of the
: machining and drilling. I have one of those
: heads on my 76 Valiant. In that case the
: hole in the back of the head is there but it
: does not go anywhere and can be left open.
:
: Look if your head had a cup plug in each end.
: About a 1/2" or 3/8" diameter
: plug.