Oh well, now the head is off, you need a straight-edge (a really good stainless-steel ruler 6" / 150mm long. Just make certain that each piston come up full height in relation to the top of the block. Bring each piston up in turn and with the ruler on edge on the block check the gap between piston top and the bottom edge of the ruler. You might want to measure with feeler-blades. They should all be exactly the same. If one or even more are LOWER than the rest, you can start thinking about bent conrods due to water inhalation.
Assuming they are OK, what next?
Critical examination of head gasket.
Critical examination or pressure test of the head itself.
If two adjacent cylinders look like they have the same problem, suspect cylinder head gasket, or some other errant connection between the cylindersm involved, like a cracked head.
Now the next bummer is the pistons - another possible damage syndrome from water inhalation is that the ring lands (the piston metal between the ring-grooves) can be broken clean off, thus crushing the top ring and land down, spoiling compression, possibly allowing oil into the cylinder, and wrecking the piston of course. You MAY be able to detect this by slipping a feeler blade down beside a piston. Put the piston down about an inch from the top to make it a little easier. NO piston should allow the feeler to go further down than any other piston. If one (or more) does, it looks like time to hoick out that piston. The difference will be very small, but you might see it.
I don't know what order to suggest further investigations, but I would be really interested to learn the eventual solution.
CharlesY
