The lead does a couple of things, its a lubricant, piston skirts, cylinder walls, valve cushioning, (both seat and stems). As you can see it works its way into the oil (combusted provides snowflake oxides) , and is circulated through out the motor. Also lead oxides are outstanding decarboners from cylinder heads to the tail pipe, used at intended ratio's.
Ive been alittle shocked at the metal count of this motor, should be half as much, the best oils have been run, with not much differnce.