The 911 SC engine I rebuilt is done in stages:
1) The "short block" encases the crankshaft and oil pump on the auxiliary shaft.
2) Six cylinders mount on the block, torqued with special long studs.
3) Six cylinder heads contain the intake and exhaust valves.
4) Two cam towers, one for each bank, contain the camshafts that operate the valves.
5) A chain case fits on each bank, holding a tensioned chain that runs from the auxiliary shaft to that bank's crankshaft.
That's just the main engine – the fuel and air delivery is another system, such as Carbs or CIS.
by Aranthar