I haven't done anything differently. My chocolate cake is exploding again!
I use DH, making it a pound cake, with flavor adjustments.
I bake at 325F.
The last time I made a choc. cake, I did it according to the directions on the box, (except for the instant espresso powder) since I wasn't home and it took over an hour to bake. I used the small ovals by Wilton and it exploded.
Exploded means I have cake batter cooking all over the bottom of my oven, just getting ready to start a fire. Yeah, it happens!
I'm not filling more than 1/2 full. This particular cake @ the moment was filled 1/3 full. I did do my full doctoring. It involves 1 box instant pudding to 2 boxes of mix.
Excuse me, I have done something different. My cakes were always made with eggs from my own chickens. I don't have my girls anymore.
How long and at what speed are you mixing the batter? Too much air will cause the product to over rise (usually shows up as a big hump, tho).