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12.2 Heater Outlet & Vents

I modified the heater outlet to enable the vent hoses to fit on properly. The heater vents were fitted later (when fitting the dashboard) so that I could experiment where to position them.

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Heater Outlet Modification

It was difficult to see quite how the vent tubes I had could fit onto the outlets of the heater which only had a very small flange. After some thought the following idea was used (photo 1).

  1. I cut two 40mm lengths of 40mm dia domestic waste tube and cut slices out of their lengths - just enough to make the tubes a tight fit inside the outlet holes.

  2. After drilling the flanges, I used two small self-tapping screws to locate each of the tubes in the outlets.

  3. I then used 40mm sections of bicycle inner tube to stretch over the vent tubes and outlets, holding them on firmly and sealing them at the same time.

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Heater Vents

There are two sizes of vent fitted to MGBs and either can be used. I chose the longer (290mm) ones which I hope will give better demisting ability. After some experimentation I positioned the vent slots as follows:

  • All centres are 275mm back from the front of the scuttle (bonnet lip).

  • For the fixing bolts, two 5.5mm dia. holes with centres approximately 65 and 335mm from the body centre line.

  • For each vent six 8mm dia. holes with centres at 80, 140, 155, 245, 260 and 320mm from the body centre line (photo 2).

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Three slots were made by joining each pair of holes with a jigsaw. Leaving 2 "bridges" helps to maintain body stiffness (photo 3). The bridges are roughly in line with vanes in the vents so should not affect airflow much.

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The vent fits underneath and just clears the wiper box and tube. The escutcheon (trim plate) fits on top and the two bolt together (photo 4). I found the studs on the escutcheons easily broke off so, when this happened, I drilled them all out and used stainless button head bolts instead.

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