My 1963 260 has a PCV valve that draws fumes off the crankcase.
Make-up air is drawn in through the original-type oil filler cap / crankcase breather cap through the oil fill tube that leads to the crankcase:
Oil Filler Breather Cap EC61 2.JPG
Is there a recommended replacement interval for breather caps?
The cap just plugs on so there is no tight seal. There has to be air leaking in around the filter. I am guessing that this was not considered to be much of an issue because (1) The amount of ventilation air would be small. There is not a powerful suction of air flowing in through the crankcase. (2) Any dust that was carried into the crankcase would be caught by the oil filter. (3) The plug on cap is easy to remove and replace when adding oil.
That being said, would a clamp-on oil filler air filter keep the crankcase oil cleaner than the original-type breather cap? Would there be much value in making that replacement?
Airraid Filter.jpg
PS: On thinking about it further, it appears that a disadvantage of the the paper air filter is that it would be relatively delicate and easily damaged if it were knocked sideways. In comparison, the original-type cap is built like a steel can and you would have to use a hammer to damage it.
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