On hot days my underhood temp. gets high enough to cause my secondaries to boil over. I put a heat diffuser under the carb, and switched to water wetter in the cooling sytem. Coolant temps never get over 210. I finally got fed up and cut about 14 holes in a junk hood with an 1 5/8" hole saw. That helped more than anything. I'm thinking my headers are radiating too much heat into the engine compartment. Any one had this problem or have any ideas?