Also added to the gunk were the slits in the valve cover causing all of the road dirt under the hood to get sucked into the vent slits. This was fixed by another GM evolution, the PCV system. There is a reason these things evolved. I know here in Kansas on the farms these trucks were in the shop alot because during wheat season, the dust was so bad and hay season when the truck is out there in the dust running all day moving the baler, they just sucked unreal amounts of dirt into the engine. Every single AD I have and have seen around here has a new style 235 in it with closed valve covers. I do not mean to disrespect anyone's stock truck. I keep saying it because its important. If you like your stock system keep it, but it's not even worth arguing over bypass systems being better than full flow. They are better than how GM sent them to the dealers. That's about it.
Someday I would love to see statistics on how GM can say that all of the oil is being filtered and not just that oil that is closest to the sump. But even if true, it's not efficient and GM realized that 55+ years ago. Just after they ditched splash oiling and babbit bearings. It's all evolution as it should be. We learn so much from it too.:)
