Rocker mushroom breather

[bobfather]

Why is the nearside rocker cover not vented into the plenum? These mushroom breathers are renowned for choking, thereby preventing pressure relief on that bank. I was wondering whether there would be any benefit from removing the mushroom and piping the rocker cover into the existing vapour recovery system, probably would need a flame trap too.

[jojackson4]

It’s air in isn’t it?

[bobfather]

jojackson4 said:

It’s air in isn’t it?

No, it's oil vapour. I guess my main reason for thinking about it is because it blocks up so easily. I don't know whether that is harmful to the engine

[Steve_D]

The throttle body & plenum pulls a vacuum on the right hand rocker cover and therefore the rest of the engines innards including the left rocker cover.
The mushroom has a very small hole to allow a controlled amount of air to ENTER (hence why it has a foam filter to prevent dirt entering).

Steve