Spark plugs

[old-tank]

Just checked the plugs in my most frequently driven 55 after 12,000 miles and expected to clean, re-gap or replace the AC44's with (?). All of the plugs had a light coat of soot and the gap was unchanged....looked like 12 miles instead of 12K. The engine was rebuilt totally (stock) when the plugs were put in....stock except for Petronix Ignition. I've been driving and tuning 55's since the mid 60's and have never seen this!Willie