hank

I have a stock block 240 that I installed triple Webers and headers on. After rebuilding them and figuring out the correct jets and venturi tubes, I now find the fuel pressure drops as the engine warms up. It starts off around 3 PSI and goes to zero, but the motor still runs. Is the fuel cooking in the bowl? I tried replacing the fuel pump, regulator and pressure gauge...$$. I also wrapped the headers with header wrap which made a little difference. Nothing like trouble shooting with the wallet. The water temp gauge says water temperature is normal. Anyone else have this problem? These carbs came out of a junkyard 260Z. They had no heat shield but I have noticed many of the Weber carb pictures on this site do not have shields. Any advice out there? signed stumped