D0ve cylinder head question?

Both my driver's side and passenger side heads have block off plates on the ends of them and they are blocking off exhaust flow, my question is why are there these exhaust passages here is if for some kind of egr setup or something. Also, on my driver's side head there is a bolt hole in the front of the head that blows exhaust out as well? I haven't noticed that bolt hole any where else on that head or on the passengers head. Would appreciate some schooling

are you they the d3ve head i havent seen dove with the air boss drilled out befor? maybe the mad portter will chime in and shed some light on this.

The california dove heads had the thermactor rail just above the exhaust ports drilled along with three of the 4 bosses in the exhaust ports.

When not utilised the rails are plugged off with a special 43/64" cup available from napa #219-2188.

The thermactor air injection system pumped additional oxygen into the exhaust to lower both H/C and CO emissions back in the day.

Is the bolt leaking exhaust in the front of the head near an exhaust port. Sometimes when heads are ported we go into the headbolt boss left of the exhaust port. At the front drivers side there are some tapped bolt holes that go into the head bolt hole. If the head bolt hole is pressurized with exhaust as a result of portwork breakthrough those particular bolts holes can leak some exhaust. Just seal with teflon paste.

Thank you sir didn't know I had Cali Emission heads but as you describe thats what they are! Also, previous owner had port work done and that is why drivers head is leaking I bet thanks for informing me of what's going on greatly appreciated