Complete Build Journal


Heater Behind Firewall

All the talk about drawing supply air from your engine bay for your heater didn't really phase me.  It's a heater.  Why not bring in warm air from the bay?

But then, the thought of having a vent fan during the warmer months was considered.  I don't want to pull heat from the engine bay during the warmer months.  Sometimes sitting in traffic may warrant the need to turn on a fan.  If that supply air is hot, then I won't use it.

However, if I can draw the supply air from an area that has access to fresh air, then it may work better for us.  So with those thoughts, I planned a layout for the heater.

Things to consider:

  1. supply air comes from driver's footbox area
  2. leave room for competition style dash layout.  that means a speedometer in the middle of the dash.
  3. Be sure that the heater lines don't interfere with the wiper motor that needs to be mounted to the firewall.
  4. Be able to run a vent to my hand that rests on the gear shift to keep it warm.  If my hand is warm, then I'm warm.
  5. Have a path for the defrost

This is the idea first considered:  

A plenum would be made to help transfer the air from the motor to the coil.  This is a Summit Heater with a 28,000 BTU rating for $149.00.  I haven't purchased the duct work yet.  That time will come.  Summit is holding it for me in their warehouse until I need it.  

But the copper may interfere with the wiper motor.

But the bigger problem was going to be the size of the plenum.  The blower would be pushing air out of a 10sqin hole into the coil.

So if my plenum isn't going to be the bottle neck, it would need to be 10" across and 1" high.  Well, that doesn't fit how I had it laid out, so I put the fan and coil box on their sides.  With this orientation, the dimensions of the plenum are 1.5" deep x 7" high.  Plenty of room.  I am planning on having a competition dash, so I've made space for the speedometer.

It has been mentioned that with this arrangement, you really hear the fan noise.  I did hook it up to a battery to hear it, and it is indeed loud.  But my thinking is that if I do need it on high because of low temperatures or cold driving;  I wont be bothered by the sound.  I'll probably be moving, and the side pipes will drown out the fan noise anyway.

So it's mocked up.  I wont be hitting the wiper motor, and I should clear the speedometer.  I'll be leaving it like this until I am able to mock up the dashboard to be sure i've left enough room.

I'm not sure that I'm sold on the diamond plate.

The copper pipe just clears the wiper motor.  With the orientation that I ended up with, I didn't need to cut that copper after all.  Oh well.
Edit:  Dan Babb had a great idea to run the heater hoses under the fender of the body.  So instead of the 90*'s shown in the photo below, I'll come straight out and through the gap in the firewall.  I'll seal it up and have grommets in place.  This way I don't need to drill into the firewall.  Thank you Dan.

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