Hi 4o Deluxe,
Even though hearing of vapor lock, & beleiving it can exists, I have never had a vehicle that could produce vapor lock in our climate.
As such, only reporting what was previously reported from previous intelligent experiences in order to help this guy resolve what so far has "not" yet been resolved.
Coupled with the manifold/exhaust heat experience mentioned in message no. 139 above, appears this is what was experienced & reported about heated fuel on 06-05-2012 at 09:35 a.m.
Vapor Lock --or vapor in a fuel line
I don't know if this applies to any or all other folks, but yesterday I fielded a phone call from someone who described some symtoms like everyone has been describing wanting some tech advice. After thinking about it last night I e-mailed him early this morning for him to call me. On a hunch based on some other feedback he was giving me I suggested that he leave the ignition switch off and while reaching across the engine, engage the starter and allow it to spin for 20 or 30 rounds with one hand while touching the fuel line with another. He called me back and said it didn't even spin 10 rounds before the fuel line got hot enough to burn his hand.
As I explained to him, he has a ground issue. My initial thinking is if the fuel line is carrying the current, then is it "preheating" the fuel in the line enough to create a vapor? Maybe that would explain how someone has 3 cars using the same fuel and swapping carburetors does not make a difference for them. Maybe that would explain how the use of engine pans can cure the problem?? While this may not be the cure in every case, I believe it is a contributing factor to one person's issues.
Carry on............. 
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BRENT in 10-uh-C
In my opinion it is a safety hazard driving in traffic with a stalling car & the quicker this gentleman can determine the problem, the safer his entire family will be.
Any suggestions?