Plug a smog hole

One of three things....either you have the wrong size tap (not likely), You have the wrong size bolt or you weren't putting enough pressure on the tap so that it continually cut threads. If you don't put enough pressure the tap will cut all the material out of the hole as you turn the tap. You didn't say if the tap went in easy or hard or if it was cutting threads. Can you see "good" threads in the hole?? It's not a big deal because there are other options and there's plenty of material around the hole.
PICS OF HOLE?THREADS??
treblig