In the valley of the block between the bosses for the knock sensors there is an allen headed plug. I assumed this went through to the crankcase but I managed to crack it open & there is a bulkhead about an inch or so below the opening. Does anyone know if this is a water jacket or just a supporting wall for strength or? I was going to use it for an oil drainback hole but I'm not sure if it goes through to the crankcase or......?

Thanks, Hammer

 

On my S4 block it is a threaded hole that goes to the main crankcase area, though you may see the supporting structure of one of the main bearings.

 

No water in there anywhere. It will drain on top of crank thrust bearing.

 

Great! Thanks guys. With the engine in the car now I couldn't check for myself.

Regards, Hammer