That passage is drilled to connect to port #2, and supplies oil to the "through the water jacket" tube to the rocker arm shaft when the spring loaded valve in the oil distributor plate opens. Any excess volume will be bypassed back to the oil pan through port #4.
Jerry


"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!