The oil catch can is used to catch 'blow by', oil vapours from the engine's crankcase build up in the combustion process and needs to go somewhere. Environmental authorities consider this an emission so it needs to be dealt with.
In the case of modern Honda engines, this 'blow-by' vapour is directed back into the intake manifold for re-combustion. The emission is 'consumed' and you eliminate it completely.
In the case of the K series engine, there is a PCV (Positive crankcase ventilation) valve that allows the passage of air FROM the air box into the ROCKER-COVER and travels down into the crankcase where the oil vapour is mixed with air. It is then directed FROM the CRANKCASE into the intake manifold where it is consumed in the combustion process.
So if you need to use a oil catch-can, you would connect it to the 'blow-by' tube located in the crankcase, NOT the rocker cover. This is true for K series engines. Older engines (and I don't know which ones) that only have crankcase ventilation at the rocker cover, which in that case is the only place to put a catch can.
When you're racing, you don't really care about emissions and you don't want to burn oil crap with your fue/air charge so you collect it in a can for later sniffing :lol:
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Originally Posted by vti-2
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