Welding on a cast iron exhaust manifold is a tricky situation. I've been welding professionally for over 25 years, and I'd be a little apprehensive about the outcome if I decided to modify a manifold. Better find some junk cast iron, and do a lot of practicing before you tackle the real thing!
Jerry


"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!