Here's a crack-ridden cylinder head sliced up to show it's innards. It's proven very useful in surveying coolant flow and where one might remove metal from ports.
All of these cracks are in the same head! Someone really did it in.
Here it is chopped into slices. These heads are getting scarce, but this one had four cracks in four cylinders and unsuitable for repair. I had it hot-tanked and media blasted before crack-checking, so it's nice and clean for photos.
My saw would take only about 9" x 9" so I could not make optimum cuts, but I got some good revealing slices. I chopped it in half crosswise (between 3 and 4, off a bit on purpose), then chopped off half of #6, then sliced the remaining 4, 5 cyls in half lengthwise, about half way through the ports.
The coolant chambers are rusty inside (nice photo contrast) and very rough. Three of the cracks are in or near the exhaust seat, closest to the intake seat. The water jack there is very poor, and tapered, and looks like lousy water flow -- but the cause of the crack is a leaking headgasket, this is just the first place to go. .
NOTE: Clicking the small photos will fetch a rather large, 8-megapixel, image. And if this isn't enough, there's movies:
This is how the head was sectioned; the pieces here are stacked together and labelled A, B, C, D.
This is the longitudinal slice that reveals the port arrangement.
These show the water jacket side of two of the cracks.
This is a typical steam hole, from the water jacket between the two valves down into the block (through the headgasket).
Details of the middle exhaust port, cylinders 3 and 4 siamesed. This port is different; it has an upper chamber that protrudes under the carb to warm it up.