You most likely cracked the cylinder head with that much heat! You definitely will need a new head gasket when you remove the head. Make sure to get it checked for straightness and magnafluxed to check for cracks by a machine shop.
98 TJ 4.7 Stroker!!! Unichip tuner, HPD30/D44, 4.56, Detroit Locker in rear axle, 3.25RC SL, 1.25BL, 1MML, 35x12.50x15, Cager Softs 15x8, XRC10 winch, Rancho 9000XL shocks with wireless remote