I've just blocked the heater outlet with a rubber plug at
present
for initial starts but was wondering the same thing.
I think others have pulled the tube from the block and
tapped and plugged the hole.
 Why not use this for cabin heat?????
Rich

I was originally going to put a heater core in the cabin and feed the
water as per Mazda's design.
I've now planned to install a standard airbox from Vans with a feed
from heated air post radiator, like Dave Leonard' in the photo. Can
Dave L comment?
In the end weight and simplicity seamed to win for me.
Steve Izett

Guys, I think what is circled in that pic is a fuel pressure
regulator, but
I could be wrong...or maybe that pic was just referenced.
Rick

Your right Rick. It got interchanged with the one steve sent. Both
pictures are the same.
Paul Lamar


 Rick and Paul
The photo of Dave Leonard's was to show the heater box and scat hose.
Steve Izett

I'm wondering if this approach (using the air from the back-side of the
radiator for cabin heat) will produce air of sufficient temp to warm the
cabin on a really cold day. Dave is in Calif if I remember right. I'd
been planning on going with a cabin air heat muff warmed by radiated
heat from the exhaust, but this has some negatives (even though
double-walled, CO safety is still a concern. Also, it can make
inspecting the exhaust more difficult).A separate heater core adds
weight and complexity, so I'd like to use Dave's approach if the air
coming out will do the job when the OAT is -20 deg F.

Mark Waldron

One of our tangential muffler designs made by Jerry Hey
has a tube welded in the center. It helps the muffler quiet the exhaust as
the gases rub on the tube and covert noise energy to heat. (That is how all mufflers
work). It also helps the rest of the muffler live by cooling
it.

Air passing through that tube can warm the cabin. I would make sure
it is .065 thick Inconel or .109 thick 321 SS and use a CO monitor.
The best kind is one that gives CO as a percentage of the air coming
through the system. This can give an early warning of
small leaks or cracks.
http://www.breathcotest.com/?gclid=CNy43YTbopgCFQHHGgodkRrmnQ

Paul Lamar