Well, the Viva heater isn't actually that bad it seems, although I haven't had much luck with the thing until now.
Generally, over the years, the heater has been O.K. during town driving but terrible on a long motorway journey when travelling at speeds over 50 m.p.h.
Although the heater motor is not needed when travelling at speed, some road dirt, salt or whatever must have got in on one particular journey.
Next day, I turn the motor on while going to the shops and... What's that burning smell? Oh dear, or words to that effect.
When I arrived home, I removed the heater box although it was clear that the heater matrix had to come out too. This meant disconnecting
the pipes and breaking into the cooling system. When I did, I discovered that, where the passenger side pipe joins the heater matrix just outside the heater box,
they were joined together with a smaller rubber pipe in between, with about a 6mm bore. This was restricting the flow somewhat! Doh!! I have since replaced these two pieces of pipe
with a single one, avoiding the joint.
After stripping down the motor, cleaning and re-lubricating it then putting the heater assembly back together again, I had a heater again, even on fast journeys.
It seems that it was myself who had put the rubber joining pipe in place as below shows a photo of the engine bay in January 1997. A piece of copper pipe may fit here. Note point 2, with the original joining piece that I broke.
Also, see point 1. Should your HB sprout a leak from the heater valve and you're not worried about originality, install a Chevette heater valve instead. You might have to reverse it so that
it matches the directions on the dashboard. However they last a very long time and there are plenty in the scrap yards at the moment. Why not get two?