Help and Tips
Some pointers to standard Minor breathing arrangements.
* The earlier cars had a pipe pointing straight down on the tappet chest cover which was the inlet for engine breathing.
* The outlet was via the pipe on the rocker cover to the air.
* The Oil Filler Cap on these engines should be solid ( i.e. NO wire filter in it.)
* The 'straight down' pipe was found to leak oil, so was later changed to a swan's neck shape which stopped a lot of the leakage.
* Later engines had a different system where the breather pipe on the tappet chest went straight to either a valve device on the inlet manifold and then to the carb. Or, straight to the carb so this was now the outlet and necessitated a change in the Oil Filler Cap which now had a wire filter in it and had become the breather inlet.
So the rules are:-
* If your engine breathes into the air filter it should have a 'solid' oil filler cap.
* If it breathes into the carb the filler cap should have the wire filter in it and the rocker cover should not have a breather pipe on it.
* These filter type caps are supposed to be changed every 12,000 miles but can be thoroughly cleaned with a good de-greaser etc.
* If the revs rise considerably when the filler cap is removed then the wire filter is clogged up.
Hope this helps...