Too much water during flush

Just moved into a new home and am doing the usual repairs throughout. All of the toilets are Crane low-flow (not sure on the model). One is driving me crazy - when flushing, so much water enters the bowl that it swirls violently and approaches the point of overflowing, getting slightly above the bottom of the rim. I have adjusted the float cup so that the water level in the tank is correct and at or slightly below the "water line" marking. Flush action is good otherwise and no leaks are apparent anywhere. Any suggestions appreciated.

sounds to me that there is a restriction somewhere in the drain. Just a guess, I'm not a pro, but the thing should drain fast enough so that it doesn't fill that much first.

You've got a clog issue going on. A good closet auger will probably clear that right up.

Good luck

A friend who recently remodeled bought two of the Crane "complete" toilets (bowl, tank, seat, wax ring and floor bolts all in one box for $99) and they both do the way you describe. If I'm not mistaken, they have a full rim flush as opposed to rim jets and, when flushed, the water drops from the tank VERY rapidly. While not ruling out a drain issue, the coincidence makes me wonder.

These are '99 models, but I think that these do have a full rim flush like you describe. I examined the other two toilets in the house and they also flush pretty violently (which I guess may be good for a lo-flo), but the water doesn't seem to rise quite as high in the other two. When I have the chance I'll give the problematic one a go with the closet auger and see if that makes any difference.
*sigh* I finally become an expert in the workings of the 1977 model Mansfield toilet (in the old house) and now I have a whole new set of quirks to deal with.