I had to laugh at this one, because a new engine was waiting in reserve when this one broke. This is the part that caused my very original quarter million mile engine to be retired after too many wars. The 1500 engine was rebuilt after 150,000 miles, having had bearings redone at least once in that time. A few repairs and another 100,000 miles later this piston gave up the fight. A co-driver and I were taking turns thrashing it at an autocross, running regularly somewhere areound the red line that day, give or take a little. The piston broke at the 4th ring groove (oil wiper ring) and left the crown stuffed up in the top of the cylinder. Co-driver was a bit concerned that it broke while he was driving, but in fact no one drives the car harder than I, so it obviously wasn't his fault. It ran fairly well on three cylinders, nice an quiet anyway, so it was casually driven home 175 miles on some secondary roads.

Look at the edge of the crown above the top ring groove, and you will see a rather large slot burned out the top like it was hit with a cutting torch. When the original distributor wore out (after a couple of overhauls) it was replaced with a Mallory Dual Points distributor. The adjustable upper limit for mechanical spark advance was installed with whatever setting it had out of the box. This gave the engine too much spark advance, so it ran hot. When the parts had a lot of wear the ring gaps were getting too wide, resulting in significant blow-by. Hot combustion gasses blowing through the gap in the top ring obviously erroded or burned the kerf in the aluminum piston crown. This may not have had much to do with the part breaking. Give credit where due, the piston was just old and had been through too many wars.

Here's another one. I've had a few of these, always fun when it happens, quick to diagnose, and various cost to repair depending on collateral damage. My Aerolite 4-ring pistons seem to have a habit of breaking at the 2nd ring groove. This one is a 5-rin piston, identity yet unknown.

Broken differential pinion shaft. A few of these have been reported. This may to be a result of a loose locking pin, possibly left loose after changing the thrust washers. When the pinion shaft slides out one side of the carrier it can hit the input hypoid input pinion gear. (Photos from K.Garner, West Midlands, UK)

Some things should be self explanatory. Not so much used and abused as neglected. This control box looks like it may have been upside down and filled with water for a while.