Quote:
Originally Posted by AWD Addict
BMW went with a poly valve cover to minimize heat soak over the block.
Stick with OE.
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and then they stuck a big insulated beauty cover on top which completely nullifies the heatsoak argument. it's more likely to minimize noise harmonics from things liek lifters and the high side rail/injectors, and that it was cheaper to manufacture so saved them money. this is evidenced as money saver in the fact they crack routinely, and the factory PCV leaks boost pressure ( which leads to pressurized crankcase, which leads to leaking gaskets from pressure pushing oil out. )
OE is not always the best.