[Jay S]

Originally Posted by Schurkey

In general, silicon is from poor air filtering--dust/dirt/sand. I'm not saying there can't be exceptions, but that's the first place I'd be investigating.

ESPECIALLY if you've got an oiled-gauze air filter that still looks nice and clean, or a modified air filter housing that doesn't seal to the air filter element properly.

I agree in those things. If there is an issue with air filtering it could be tied right to the lead also if the engine inhaled something and some particles made it to the bearings. The trimetal bearings only have about a .001” thickness to get the the layer that contains lead, then the lead will leach out and raise the ppm in the UAO. Most main bearings used in Pontiacs are trimetal.

Silicon is used in bimetal King SI and HP bearings, and all the EngineTech bearings. I have engines with King HP rod bearings and trimetal mains, so it is possible to have higher levels of lead and Silocon from bearing debre with some combinations of bearings.