Safe to ride with broken exhaust manifold bolts?

So...

About a week ago, I noticed an exhaust manifold nut had backed out of the stud and got left on the highway. None of the local shops were open that day, so I removed the other nut to go get something with the same threading from Ace as a temp fix.

Surprise, when snugging the collar down, a stud snapped off below the level of the head.

A few days later, the other stud either backed out or broke. Not sure as I heard the stud depth was about 3/8" and the hole looks about that deep.

Obviously I have an exhaust leak now. Will it hurt anything or just sound annoying? I've heard stories about cold air infiltrating exhaust manifold leaks and warping valves, but I've never really felt that made a huge amount of sense.

Also, should I even try to drill or try alum? I'm not sure at all about making a workable bath out of modeling clay, at least without removing the engine and standing it up. Can somebody reassure me that this is doable?

 

Alum first , then you probably won't need to drill. Sticky-Tack might work better than clay in this instance. It will adhere to the engine for as long as you want it to.

The smart part of my brain says fix it now before you end up with more trouble because of the leak (that cylinder will run a little lean).
The lazy part of me knows that I ran a GM 350 for two years with a warped exhaust manifold and didn't burn a valve (but that was an all-iron 350).