In response to the vapor lock problem put forth by Ron Thomas in the December 1977 Roundel, I can offer the following.
I had the same problem with my ’72 Bavaria and suffered with it through the summers of 1972 and 1973. I tried insulation as you did with no success.
The solution as suggested by my BMW dealer, Autosport by Juri, Vestal, New York, was to replace the mechanical fuel pump with an electric one located on the firewall near the windshield wiper motor, not on the engine compartment side. I’ll leave it to common sense to figure out how to route the fuel line.
Power for the fuel pump is obtained from the ignition switch side of the ballast resistor as there is an extra spade connection available.
After this installation I have not had a single vapor lock nor have I had to provide any extra fuel line insulation.
Author: Paul and Kathy Vasek