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[PLANETNZ]

I realise there's the whole MOT emissions thing with you guys in the UK, we dont have this here so is there any reason the crankcase cant just be vented direct to the atmosphere and block off the top?
Aslo, how are the heads themselves vented, im guessing theres an internal cavity from the head to the crank case?
Cheers

[chrisgixer]

The breathers allow the crank case to run at negative pressure from the inlet. This won't be possible if bypassed. So any oil leaks will get worse.

[Kevin Wood]

The main reason you need good crankcase ventilation is to ensure vapours from combustion are drawn out of the crankcase. If this doesn't happen, acids and moisture will build up and can lead to corrosion and degradation of the oil. Older engines had the crankcase vented to atmosphere but in a day when vehicles did less mileage and had more regular servicing.

The modern system of using intake vacuum is much more effective, leading to a healthier engine, and also has the advantage that the crankcase is kept below atmospheric pressure which helps the oil seal remain dry.

I think you need to turn the argument round and ask what can be achieved by going to an open breather. I can't think of an advantage of doing so.