I feel the first step is a refresher on the
terms commonly used to lablel the
nastys within the as cast passage.
click for a big picture
On post '73 castings.
the thermact-air bump
is drilled to carry air
from the smog pump.
Passage is accessed
from firewall side.
Passage is plugged on
front side  with a small
welsh plug
On post '73 castings,
the thermact-air boss is
drilled to carry air from
the roof passage and
inject it into the port.
Adding oxygen to the
exhaust stream helped
to complete the burning
of  the unburned
hydrocarbons.
click for a big picture
Note drilled hole in t-boss. This D3VE-A2A head is
from a '75 A code Ranchero
home
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Step by step porting guide for D0VE passanger car castings.
This is the first of multiple sources of information. Read them ALL
before attempting to port your castings
There are subtle differences from
the early to the late castings with
regard to short turn shape as cast.
These differences are note
throughout the guide as a "Whole"
Read all 5 guides BEFORE
starting your porting project
index