I've been running 300zx pistons for about 25k now. The plugs were brand new after the rebuild and were stock nkg's. I was taking my engine apart for a head swap and the #3 spark plug was missing part of the insulation and part of the spark arm. Well when i finally got the head off, the cylinder was scored pretty badly. First off is the damage done repairable? The grooves arent that deep but i don't have a bore scope to check it. Secondly what would have caused this? The copper on the spark plug looked like it had suffered from electrolisis. I had the timing set between 15 and 17 with a jwt ecu program. Thanks,
Jason
Jason