Alright so my todo list is
Remove head and verify headgasket failureTear down valve trainWash and surface head (via Thornleigh Cylinder Heads)Check valve stems, lap valvesReplace all head seals and gasketsCheck valve lash and adjust/replace shims as neededClean block deck, inspect for warp or other damageInspect block water jacket in light of apparently hot #4 cylinder and remove any obstructionsClean intake manifold
I went in with the borescope as initially thought it might be something like a stuck valve, here are some videos. NB you may think you see green on the piston crowns, but it is an artefact of the camera, it is just carbon/oil buildup.
https://www.youtube.com/watch?v=BkRc2aUt6ww
https://www.youtube.com/watch?v=cSxqQnZwXGY
The bores generally look okay without being great. In my experience the motor will run fine for a long long time with the bores like this. Compression on cylinder #1 and #2 is zero. 3 and 4 were both showing 130psi (stone cold engine). You can see a little bit of corrosion on some bores probably from the motor sitting for years. I'll inspect once the head is off but the hone looks pretty good and usually that augurs well for the block as a whole. The motor turns over like butter by hand.
Spark plugs (Top-to-bottom: 4, 3, 2, 1). 2 and 3 look good to me, 4 looks like it's been running hotter, and #1 is a dumpster fire.
Otherwise oil smells good, no sign of coolant in oil, no sign of oil in coolant, no sign of fuel in oil, no sign of fuel in coolant.
