M60 stock crankcase ventilation valve problem: its design fault and insufficiency for performance tuning

There are excellent articles out there about faulty Positive Crankcase Ventilation (PCV) systems, like the one on Timm’s BMW E38 Repairs and information page. PCV or Crankcase Ventilation System (CCV) is basically the same valve with a different name, only acronyms may vary.

This article is from the perspective of performance tuning. If you are about to install hotter cams, raise compression or rev limiter, it is important to understand the design flaw in a stock M60 PCV system. The described mods typically increase engine performance, but also put more stress – and blowby – through the engine. These blow-by gases are the reason, why there is a system called Positive Crankcase Ventilation in the first place. Thus, when you increase stress to your engine by increasing both compression and rpm, you will increase the amount of leaking gases to a crankcase. This will put increased demand to PCV system to do its job.

Unfortunately, the stock M60 CCV design is faulty from the factory. It does not matter if you replace the item with a new one – it is not up to its task, more less when you are doing any performance upgrades.

The main havoc for the stock PCV system is the design: all gases and residue will accumulate in the front of cylinder 8 runner. When there is enough sludge, and you accelerate hard at the same time, the cylinder in question will gulp all the residue into the combustion chamber. The result is pretty obvious: the Pope like white smoke is a testimony of compromised combustion chamber process, with excess oil.

Installing an oil catch tank

One option is to bypass the stock PCV valve, and install an oil catch tank for residual gases. This can be done by modifying the stock PCV valve, and rerouting gasses to the tank. Other option is to purchase a new rear plate for intake manifold. The oil catch tank was acquired from BjörkMotorsport.