The Pinto heater is a simple design with no bells & whistles that works quite well.  It only works in a “fresh air” mode, with the air coming into the system from the chamber in the cowl in front of the windshield into the far right of the heater.

Temperature is controlled by mixing cold air with hot air.  A vent (arrow in the picture) directs cold outside air toward the heater core to be heated or into the mixing chamber.  In the picture, the firewall side of the heater is up and the passenger side is down.  Hot and cold air are mixed in the cylindrical chamber that bolts to the firewall.



From the factory, the mixing chamber has a flare (bell-shape) intruding approximately ½” into the chamber.  There is also a gap of approximately ¼” between the fan and that flare.

I started out by putting a 2” sanding head on a pneumatic die-grinder (straight – not angled) and with a 24 grit disc, sanded the flare off, so that the firewall side of the mixing chamber was flat.

The material at the point where the two chamber meet is three thicknesses.  So, I put a light-weight wood cutting rotary rasp into my die-grinder and slowly increased the size of the hole over the size of the reinforcing ring which is the third thickness until it was very slightly larger than the blower motor fan.



I determined that I could now move the fan into the mixing section 1”, so I used a hole saw to cut the round raised motor mount section off of the motor mount plate.  I then cut  a 1 1/8” section of 3 ½” OD exhaust pipe and welded it to the motor mount plate and then the raised section previously cut off onto the tubing.  This placed the edge of the fan flush with far side of the triple-thickness wall of the mixing chamber (inside the enlarged hole in the picture above).



Assembled and installed, it blows lots of air out the heat vent and through the defroster vents.

As installed in my Pinto (and where my engine appears to be slightly more rearward than some others), there is about ¾” of clearance between the heater motor and the exhaust manifold and the same for the oxygen sensor.  If one should lower his engine 5/16” as recommended by Bill (and I’m thinking very strongly that I will), there would be another ¼” or more of clearance.  (Yes, I have to rotate the motor to move the wires away from the oxygen sensor.)

 

Mike