John;
I have argued the vapor lock issue with many. Most folks who believe they have a vapor lock problem do not but instead have another problem incorrectly diagnosed as vapor lock. I have my fuel line from the pump to the carburetors routed well away from the exhaust manifold. It is located in an area where the air flow from my radiator electric pusher fan supplies it with ample air flow to prevent the fuel in the line from boiling. I have driven my car in 95+ degree ambient temperatures with no vapor lock issues. In my opinion the clothes pin trick only makes the owner/driver feel better.
