Here's a recipe for Sweet Pickled Carrots from Better Homes & Gardens "Home Canning Cook Book" c. 1973. I prefer to make it with baby carrots, but it works fine with sliced and they are crisp. I'm sure you could switch up the spices and make them dill if preferred - but I would not lower the vinegar/water ratio.
Sweet Pickled Carrots
Peel 6 pounds medium carrots (about 36). Cut lengthwise into quarters. Cook the carrots in boiling, salted water just till tender, 7 to 8 minutes; drain.
ETA: I cook them until a fork will pierce them slightly, but not until cooked through - "al dente".
In 8 to 10 quart kettle or Dutch oven combine
3 cups sugar
3 cups vinegar
3 cups water
1/3 cup mustard seed
7 inches stick cinnamon
6 whole cloves.
Bring to boiling; simmer 20 minutes. Pack carrots into hot jars, leaving 1/2 inch headspace. Cover with vinegar mixture, leaving 1/2 inch headspace. Adjust lids. Process in boiling water bath (pints) 10 minutes. Makes 6 pints.
Regarding canning plain carrots - that should only be done in a pressure canner. They're a low acid food and are not considered safe in a water bath unless pickled.
How long did you process them? And were they hot or raw pack? They will cook in the pressure canning process. However, I've found raw pack for pressure canned items does help some, and don't process them any longer than required.
Here's a link with tested, recommended processing times.
http://www.uga.edu/nchfp/how/can_04/carrots_sliced.html