My home inspection of Speedmaster heads

Since it's a head thread, we can talk valve train parts as they 'could be' upgrades or alternatives... I bought a set of engine pro "nitro black" exhaust valves to replace the ferrea 5000s I was running.. what do you think about those? I hear they hold their shape better under extremes..lol

no clue.... lol
But Ferrea makes really nice stuff. Made in Argentina