Mike,
The heater should be doing much better than you describe its
performance today. It can do a pretty good job, at least it can put a
fair amount of hot air through the heater box outlets. Once into the car,
the heat dissipates rapidly, but certainly it should be able to make your
ankles hot, if not uncomfortably hot. For several winters I drove my '75
year round, in coastal Maine, and found that the heater did its job.
Is your engine running at correct temperature, needle centered on N or
center of the temperature-calibrated gauge? If not, changing the
thermostat and blanking off part of the airflow through the radiator may
be called for, to get the water temperature to at least 180 degrees. My
B now has a 195 stat in it, and I find that part of radiator must be
shielded to get to N on the gauge if air temperature is in the 30s (F) or
below. Once the temp needle is there, the heater produces plenty of hot
air.
Do you know that the heater valve is opening fully? The knob doesn't
always move the valve to fully open or fully closed positions. Though I'm
sure that it can be adjusted to do so, I never figured out quite how, so
moving the outer cable in the clamp on the valve is a seasonal operation.
Do you know that the heater is free of sediment? This heater that now
works so well was weak until I ran water from the garden hose through it.
An amazing amount of rusty sediment/mud came out as a thick paste. Once
that was rinsed out, the heater worked much better.
There are a lot of holes in the firewall of an MGB, many of which were
not used and were plugged with rubber plugs. My cars have had others too,
DPO holes, one suspects. Plugging them with silicone sealer has helped
reduce draughts immensely. Strangely, those draughts were cold in the
winter but warm in the summer. Try propping the bonnet open on a bright
sunny day, then looking for light spots under the dash.
Another source of cold draughts is from the pedal box. One assumes
that they sealed well when new, but they may not be sealed at all now. In
the Moss catalogue you see a sealing strip for the pedal box. It helps.
Further, cutting a diaphram of rubber or foam that has slits for the
pedals to swing in and bridges the large square hole will help a lot. I
have used the thin foam sheeting that is used to wrap glassware.
Replacing the under-dash panels directs the heater's output toward the
passenger area. It may also shield some of the draughts that could not
be identified.
The MGB heater has won no heating efficiency awards of which I am
aware, but it can be made to keep the car quite comfortable on grey days
when the air temperatures is in the low 30s.
Bob
snipped
> Anyway, the hamster breath heater in the MGB was running at its peak
> performance and we were still pretty cold. It did generate enough
> heat to clear the windscreen and at times would run warmer than at
others.
> Seems as we cruised at highway speed the air temp it was putting out
would
> drop to a very chilly blow and if we idled for a while or climbed a
good size
> hill it would turn tepid warm again.
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