Oldfeller--FSO wrote on 02/21/12 at 09:54:06:Does this manufacturing hole have chrome over it / in it? If so, leave it alone, it isn't going to "rust out".
Mine has one of these manufacturing "hanger holes" -- it goes nowhere and does nothing to the function of the system. Has faithfully done nothing for years and years now.
As the interior gets quite hot, it's probably a vent hole. Otherwise pressure could build up and blow out the shell.
Welding it close could cause a problem, as it may vent slowly thru somewhere else. And when it cools, it will colapse the shell.
and, you're not supposed to weld chrome.