Just two questions here fella's. I always like other opinions.

1.Gas valve making terrible noise, but still works.

4 1/2 Inc W.C Outlet. What causes such a noise? Slugging of the Gas valve? Or was it not purged corectly?

2. Flame roll out. On older standing pilots even newer ones, what the main over cause of flame roll out, out of the burners. Crack in heat exhanger? Dirty Heat exchanger? Crossover not possitioned right? Dirt and sediment mixing with oxegen and fuel causing a back draft?

any coments would be appeciated. Thank you.