Interesting tidbit, as well - that slotted rail along the driver's side got me thinking about a little observation I had made way back - the majority of the oil drainback from the head is on the driver's side. Now, I haven't given this much though before, but here goes:
The oil is picked up from the sump, sent through the filter, and part of the pressure is bled off to feed the mains/rods, and part of the pressure is bled off to feed the cams (and obviously the pistons squirters and turbocharger)
That said, the block pressurizes first - forcing oil to the cams, and to the main bearings (if I'm thinking of this correctly) - then through the crankshaft to the rod bearings, right?
The block also feeds the head via the camshafts. With the majority of the oil coming down the driver's side, it's really obvious why they built the slotted side on the driver's side of the GrpA oil pan. Also, the crankshaft's rotation will help pull that oil down - pretty damned smart of them.
The real key seems to be a way to keep the oil around the sump, allow oil into the sump, and slow the oil from leaving the sump (except by means of the oil pump itself)
The design of the stock pan prevents the oil from really getting any where under hard acceleration or deceleration in a straight line - it's in the twisties that I can see the oil getting away and allowing air to be sucked up into the pump pickup.
And thank you Ian! You are the man
