Pulled the motor out this weekend and took everything apart. The head has been taken off before since it had felpro gaskets but the bottom end still had the original nissan gaskets and looks like it hasn't been touched.
I still need to clean everything up for closer inspection and measurements but piston #1 will definitely need to be replaced.
L20a on the stand.
Valve cover off - so far everything looks good.
Head removed.
Front cover, water pump, alternator removed.
Oil pan removed.
Crankshaft and connecting rods ready for removal.
Bare block.
All Done.
Now for the damage - Piston #1 is completely wrecked. The sideskirt and top of the piston are cracked. The second compression ring is wedged tight into the ring land.The top of the piston and the head both have the same indention.The connecting rod is also very stiff. I still need to gauge the block to find out if it will need to be bored. If a foreign object made it into the cylinder I would think there would have been more damage to the head.
The two rounded indentions are valve relief cuts. The notch on the right is also supposed to be there. Everything else should be smooth.