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Definately need breather in one cover and PCV in the other or you will end up with oil film all over the engine. With neither you will be blowing oil out of every seal in the engine. Running the PCV wil not make any difference in the way the engine runs so why not do it right.




I agree with the first part, but not exactly the second part.

A PCV system is a controlled vacuumleak and a motor will idle slightly higher because of that. Just squeeze the PCV-hose on a running engine and listen the RPM drop a bit.
Also, especially on older engines, the PCV system draws dirty oily blowby vapours into the intake. This can and usually will deposit on the backsides of intake valves and can cause serious buildup if the engine is very worn.

But ofcourse it is still advisable to run a PCV otherwise moisture will not be extruded from the engine crankcase sufficiently and this will cause the famous white sludge on short trips or in colder climates.

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