exhaust valves

What situations can cause the transfer of aluminum to the exhaust valve face? its on all 8 exhaust valves

Lean or low timing.

Generally a very lean condition, especially when one is spraying nitrous. The aluminum comes from either the piston tops, or from the chambers. If you clean the chambers carefully you may see some porosity holes in the casting that weren't there before. They tend to be more commonly found in the cuspid between the two valve seats. That same lean condition also tends to blow head gaskets.

Charlie

timing was at 32 degrees it was very lean at least looking at the plugs