The camshaft covers have a huge oil gallery(?) over the timing chains. It is blocked at both ends with freeze plugs.You can see one in the first photo & the other in the 3rd photo.Does anyone know what they were intended for ? They appear unused but very large,expensive features that surely must have had a purpose ? Turbo oiling system ? alternative Vario cam system? an aux oil pump/

 

Automakers seldom machine a feature they don't need or use. Oftentimes a hole that is plugged like you see and doesn't appear to serve a useful purpose arises when it is machined to intersect a feature in the casting then the hole is plugged.

However, if this the case one can usually deduce this by carefully examining the casting for the of some feature that was intersected by the hole. From the pictures I don't see this but one has to spin and turn the thing over and over again to build up a 3-D/x-ray image in his mind of what the casting actually is.

Another reason the hole exists but is plugged is the hole is just machined because something behind it needed machining. After this machining operation is complete then the hole is plugged.

 

Schnell, I think you are refering to the oil return passage to pump oil out of the head drain sump back to the main oil sump.

 

Bill,
If you look at the photos 1,2 & 3 , there is an "L" shaped hump in the casting. It is plugged at both ends with a freeze plug. Inside the cam cover, this hump is connected to the inner areas of the cam cover. It is located immediately above the timing chain Exhaust sprocket. It must have had a use in another application of this cam cover ? Yes ,as you suggest ,some king of drain? It remains a mystery that only the M96 experts may know the answer to.

 

Well, I'm not positive... But I'm fairly certain that is the intake for the scavenge pump. The passageway connects the suctionport on the side of the pump with the lowest spot on the cam cover.

 

Dan,
You may win a cold one- you speculation seems likely.
The freeze plugs are just a distraction. It is just a way of collecting oil from the inside-top surface of the cam cover and channel it into the scavenge pumps .The Scavenge pumps have a slot in the top to receive the oil that flows down this mystery part of the casting.
Don't you hate it when you can't figure out how something works ? Thank you for your suggestion.

 

Yes, that's what I was trying to say.

One of the design criteria for the M96 engine was to drill all oil passages internally with a minimum of repositioning of fixtures.

 

Bill,
O.K.- you both get a prize !
Thank you both for explaining this .Now back to serious Boxstering.