In my experience, those "aluminum welding/brazing" rods rarely work well for anything we might use them for on our engines.  One guy reported he could get fairly passable welds if everything was done absolutely perfectly, but that it was brittle and would crack with very little vibration.  It would be even tougher to try to fill holes with it.  It is sometimes difficult to fill holes even in steel with conventional gas welding or brazing.  It is hard to get the bottom of the hole hot enough, and when you try to feed rod to the bottom of the hole it melts to the sides, filling the hole before you can weld into the very bottom of the hole.</p>

Better to see if you can go the next size up with new holes and threads on that cylinder.</p>

AV8TOR</p>