Heater tap conversions

Articles supplied by Jilden

• Many P76’s have missing or seized heater taps, compounded by the wearing out of the mixing flap seals in the heater. The result of this is a leakage of heat into the car during summer that can overwhelm the best air conditioning.
• On my car with factory air, I used a Falcon XB manual heater tap, which lasted about eight years before jamming in the open position. Unfortunately, it operates with the dash control upside down, which fools other drivers of my car.
• On the wagon, which has an under dash air conditioner, the trip to Sydney a few Easters ago sure showed me the problem. While gas converting various Falcons over the years, I have replaced many vacuum operated heater taps, which cost surprisingly little from Repco (Part no. HA5217). So, I fitted one to the Wagon with an arrangement of tee pieces to allow the LPG to get water. To operate the tap, I fitted a vacuum valve off an XD or XE Falcon heater system. On the Falcon, the valve is fitted behind the glove box, sending vacuum to the heater tap to turn it off when the control is put to “cold”.
• This works well on the wagon, so that when the control is moved just off cold, some heat comes out. I fitted the vacuum valve to the right hand side of the heater box under the dash, just under the mixer flap lever.
• More recently, I found that EB falcon V8’s use a four port vacuum operated heater tap. This type of tap lets water circulate through when the heater is turned off. On my wife’s P76 I fitted one of these, costing only $40 or so from Repco. The tap fits neatly against the firewall where the hoses come out, allowing the LPG converter hoses to be connected in series, making the job neat and simple. The vacuum valve is screwed to the side of the heater, and a one-way valve in the vacuum line to the manifold lets the tap stay off under acceleration.
• A note on plumbing LPG converters is relevant here. When fitters use the bypass hose on the front of the inlet manifold, the water flowing through the bypass is greatly reduced. This causes various parts of the engine to heat up unevenly, until the thermostat opens and lets a rush of cooler water in. I traced quite a number of head gasket failures to this type of connection. The flow through the bypass is what keeps the engine temperature even when the thermostat is closed.
• On my two sedans, I have fitted a six-cylinder type thermostat, with a bypass plate on the bottom. When the inlet manifold was off, I drilled and tapped a hole directly underneath the thermostat and connected the bypass hose there with a special fitting I made. This means that the bypass works as intended when the engine is only warm, and is blocked off when the engine is hot, giving better cooling.
• When fitting new heater hoses, sleeve up the heater connections to 5/8 inch using thin rubber hose; the bit of ½ inch hose between the petrol tank and filler pipe from a wrecked P76 is ideal for this. Use a VC commodore heater hose on the back of the engine; it has a flared right angle end and looks very neat.
• Regards, Jilden.

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