The most comprehensive description of the breather system I’ve seen is believe it or not in Haynes which basically states that the smaller pipes are for extraction of gases and the larger for air into the engine, but under full throttle all pipes are used for extraction.
I could imagine that when the engines were new blow-by gases were minimal but as they age perhaps slight enlargement could be beneficial.
Cam-caps blowing is often terminal, and here we have problems of water vapour freezing in the pipes or inlet manifold, so I’ve bothered to lift the cam covers.
Regards
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