Figured I'd add to this.
Years ago when I bought the bus(1984 6.9 idi), it wouldn't start without ether. The wts light would come on for a few seconds and go out. I knew it had glow plug issues so I oredered a set on the way home before any diagnosis. The plug I ordered were the AcDelco # 12g because I read at the time they were self limiting and knew that if it was the module, I'd just switch it over to a push button, install the new plugs, and run it. Well, turns out the module was trashed but the plugs were good so I did the manual button mod without changing to the 12g's. This went well for several years.
A few weeks ago I went to start the bus because I had to move it. It was 15*F outside and I held the button for 15 seconds which was most likely too long. Tried to run, but would't. Used a little ether while cranking and away she went. Anyways, I checked the plugs and had 6 of 8 dead. No biggie because I had the 8 new 12g's sitting in a box.
Last night I went to do a test run on them before install. What a mistake
Using a 12v jump box, I hooked all the plugs up one at a time, negative lead on the threads, positive lead on the spade, 10 seconds on and then 2 minutes to cool off.
First two went okay, the tips that were orignially square cut, ballooned out and became rounded, but didn't swell diameter wise. I heard some sort of puff like pressure release, but no big deal I thought.
3rd one exploded the end of the tip completely off, hitting me in the lip
. Fortunately I had safety glasses on, which is pretty rare for me. After that, I modified the test to start holding them inside a piece of schedule 80 black pipe instead of out in the open.
4th one lit with no surprises like the first 2.
5th one exploded as well, but this time the tip stayed on.
6,7, and 8 all acted like the first 2.
Now, here's the kicker. After testing the remaining 6 a 2nd time - 4 lit, 2 didn't. 3rd test with remaining 4 - Only 2 lit. Tested the 2 workers 2 more times for a total of 5 lights, and the remaining 2 stayed good.
So, use this info for what it's worth. But the 12g's are definitiely not an option in my opinion. Yeah, no swelling, but having them explode/give up the ghost that quickly is just as bad.
I googled "12g exploding" and found some forum hits and a youtube video sharing similar experiences. So my experience isn't unique. I think the next step is to try the acdelco 60g's because I see none of my parts suppliers list the 12g in stock anymore. I think the 60g is self limiting as well, so hopefully they go as planned. If not, I'm not sure what I'll use with my push button. Not really a fan of the 6v plugs because of the lack of self-limiting, but I'll use what I have to.