After eating large meals, I have rapid heartbeat. Is this normal?

Yes. After a large meal, the body needs to shunt additional blood to the stomach and intestines to facilitate digestion; often times, this translates to an increased heart rate to increase the overall cardiac output of blood to meet the aforementioned demand.
No, it's not. I would advise you to see your doctor to determine what kind of heart rythm you get after such a large meal.