Why is the 2" hole bored parallel to the housing
instead of perpendicular to where it is penetrating
the housing for a smaller overall hole?

The air is actually flowing upwards as it enters the housing.
A perpendicular opening would force the air to make more of
a right  angle. That is one reason. The other reason is it easier to set
it up on a mill table :)

A third reason is that is the way Mazda did it on the Le Mans engine.
See the attached drawing.

It is probably not that critical because some p-ports with
perpendicular holes also seem to generate about the same amount of power.

Paul Lamar

Paul is correct and as I'm just going through that process, I might mention
that to angle the inlet does play with the port timing and the shape of the
opening somewhat.
I don't think we need additional overlap by taking the opening lower, This
is what it seems to me to be doing as you are restricted by the oil inlet
hole, just about the position of the P-Port.
Although looking at Paul's drawing it does seem to have just a slight angle?
George ( down under)

That is Mazda's drawing.

Paul Lamar

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