Hole in piston

[Ian Williams]

I think you can discount my theory Colin, I took and old piston today and skimmed a ridiculous 80 tho off it, I then hit it with a ball pein hammer in the position yours was holed, it took quite some force to break through. The area of the hole would be the thinnest part of most pistons I have in my scrap box, (I have quite literally dozens!) and after machining 80 tho off the crown was still 100 tho thick. I am now feeling that Ian McGowan may be on the money, will be most interesting to learn what the actual cause turn's out to be.