You really need an instructor. A glow plug should not be over tight but yes, it has to be tight. I have seen people over tighten to the point the threads were warped or angled up, that is almost a strip job, over tight. LA engines are great. It's a plain bushing they use for a bearing and the engines last a very long time, not forever. When one is starting to wear out you will be seeing a lot of gray color in the exhaust, not to be confused with a loose muffler, it will start spitting out gray slowly and as time goes on more and more. I have a couple of old .40 LAs that are worn out from use in over weight trainers over a number of years, they still run and get used once in a while. I used a lot of the .46 LAs in my fun fly planes and have never worn one out. The loose glow plug is the point of the fuel blow out. I used a lot of the .46 and the first thing I did after pulling the engines out of the box was to remove the head screws one at a time and use lock tite on them. Every one of the engines I had would loosen up the head screws right away unless I did this.