The MGB GT V8 heating and ventilation system uses a heater matrix in the dashboard area, fed with hot coolant from the engine via heater hoses. A control valve on the engine regulates coolant flow into the heater matrix, providing temperature control via the dashboard heater control. A blower fan inside the heater box draws air from the engine bay area, passes it over the heater matrix, and distributes it via vents in the dashboard and footwells. Fresh-air vents in the dashboard provide unheated air supply for ventilation.
V8-Specific Heater Valve
The MGB GT V8 heater valve operates in the opposite direction to the MGB 1800's heater valve, a V8-specific feature reflecting the V8's revised cooling system layout. The valve regulates hot coolant flow into the heater matrix in response to dashboard control input. The opposite-direction operation is part of the V8 specification and is not interchangeable with the four-cylinder MGB heater valve, despite the two looking similar externally.
Heater System
The heater matrix is a small radiator with hot coolant from the engine flowing through it; air drawn through the matrix by the blower fan is heated by contact with the matrix surface. Heater matrix integrity is important, a leaking matrix dumps coolant into the cabin and may also cause cooling system pressure loss. Matrix renewal requires dashboard removal in most cases.
Heater Hoses
Heater hoses carry coolant from the engine to the heater valve, from the valve to the heater matrix, and back from the matrix to the engine. The hoses age in the engine bay heat and should be inspected during routine service. Heater hose failures cause coolant loss and can be a significant problem if not detected, the hoses are typically positioned where coolant loss runs onto the road rather than being immediately obvious.
Vents and Controls
Dashboard vents direct heated or fresh air into the cabin. Heater controls comprise the temperature control (operating the heater valve), fan speed control, and air distribution control (selecting between footwells, demist, or dashboard vents). The controls are dashboard-mounted with cables or rods to the various operated components.
Sub-Sections
Heater System covers the heater matrix and box. Heater Hoses, Valve and Controls covers the related components. Vents covers the dashboard vents. Upgrades and Alternatives covers heater system improvements.
MGOC Spares
MGOC Spares supplies the full range of MGB GT V8 heating and ventilation components, see individual sub-sections for details.