Hi there, on request I want to explain with this extra post how the PCV works on my TR4A. Here we go. The "Positiv Crankcase Ventilation" valve is a active low pressure reducer valve and not a relief valve, what I've been often told. It connects the inlet manifold with its low pressure with the rocker cover and crankcase to suck the vapours out. To avoid to suck out too much gas it reduces the "high" low pressure in the manifold (1.0 to 0.3 bar absolute) down to a l