Vapor Lock???

[protour73]

So I started to notice a drop in fuel pressure. First I replaced the fuel pressure gauge....nope. Then I replaced the mechanical fuel pump thinking a failed diaphragm....nope. I remove all of the braided fuel lines from where they come off of the hard line and checked for blockage.....nope. Checked the fuel filter...nope. Then there is always the sender in the tank (brand new 6 years ago with only 1500 miles on it). I have a small K&N filter tee'd from a vent tube off of both sides of the tank. No vented gas cap, but then it never was on a 73 and I've had no issues previously.

Fuel pressure starts out at 6psi when the engine is first fired up and stays there for about 6 or 7 minutes and then starts dropping slowing 5....4.....3.....2 1/2psi and stays there after about 25 to 30 minutes of idling. The bowls in the carb stay full even after running the RPMs up several times and cracking the throttle several times.

The fuel line runs past the passenger side headers on the frame rail......vapor lock? I have never noticed this previous to now, so I don't know if this a new issue. I can buy something like http://www.heatshieldproducts.com/pr...-shield/102/43

Thoughts? Theories?