Excessive steam out my exhaust on warm start-up and idle was the only symptom of bad reversion on my old 496.

edit: Steam was the only indication something was wrong until I drained the oil and it came out in thick blobs! I had made a stupid and uninformed exhaust modification. I fixed that and the engine was fine. No steam after.

Water in bottom of exhaust manifold is most likely bad exhaust riser, bad riser gasket or cracked/rotted exhaust manifold.