Rocker cover breather

[lancelin]

Hello, can anyone tell me why the passenger side rocker cover breather is just a very small hole and filter? Why isn’t it a bigger hole or plumbed into the air intake like the other side. This is how the old P6 rover V8 was implemented.

Edited by lancelin on Saturday 22 May 15:47

[bobfather]

To minimise air flow into the intake manifold. Old carburettor fuelled cars did not use air flow meters to manage fuel ratios so random additions to the intake air didn't make any real difference. Injected fuel systems accurately measure air and so the rocker breather air must be minimised as this is additional to the AFM air

[bobfather]

For the sake of completeness

The offside rocker cover is kept under vacuum via the flametrap outlet pipe which is pipped to the plenum intake. This removes oil vapour etc. from that cover. By way of internal passages the gas space of the nearside rocker cover is connected to the offside rocker cover. Having a small airway on the nearside cover allows that gas space to sweep vapour across the engine to the offside cover enabling vapour from both covers to pass through the flametrap and into the plenum intake

[lancelin]

Great, thanks for explaining, so making the air hole bigger on the offside is not a good idea. I guess it all comes down to a pressure difference, so crankcase gas will flow from a high pressure to a low pressure and out through the flame trap. I’ll leave that small hole as is. Cheers.

[GreenV8S]

This engine has a positive crank case ventilation system. This needs an outlet which is connected to the intake to provide suction (via a check valve) and a fresh air intake vent. The intake vent is usually positioned as far from the outlet as practical so that the PCV system pulls air across the whole engine.