Quote Originally Posted by SubGothius View Post
There was a bit of confusion on that thread, conflating vapor separators with return-line provisions. The fuel filter with the third, smaller hose barb would be a return-line solution, tho' I suppose it could kinda work as a separator if the third barb is oriented to the highest point on the filter. Since you already have a quality filter, you could just get a tee with one smaller barb (1/4" IIRC) and connect that to your stock fuel-return pipe.

The idea there is to keep fuel constantly moving thru the lines at all times even when fuel delivery is slow, such as when the carb needle valve is closed or mostly so, which can happen at idle or sometimes at low-RPM cruise. Then fuel is never sitting still in the lines where it can soak up heat and boil into vapor, causing vapor lock.

There's a good wiki article explaining it in detail:

https://en.wikipedia.org/wiki/Vapor_lock

All that said, I'm not sure vapor lock is your issue, as I did the Weber 32/36 conversion and eliminated/capped my return line, and AFAICT have never had an issue with vapor lock even here in Tucson where summer temps get well into the 100s.
SubGothius you're right about confusion regarding those three connector fuel filters; they are intended to connect to the fuel return line and/or provide a way to install & use a return fuel line... A fuel return line prevents fuel from just staying under the hood in high temps during idle 'n slow moving traffic... I noticed the OEM fuel pump has two outlets one to carb & one (with a small orifice) to fuel return line via nipples on the carbs accelerator pump cover...

Long but interesting YouTube videos about vapor lock & Weber carb mentioned:
https://youtu.be/Gqwb6U8vQfA?feature=shared
https://youtu.be/Zo24KUDYzCs?feature=shared