What is the correct rubber fuel line size for fuel return

[pyite20v]

On my 72 the rubber fuel line return line that comes from the engine and connects to the metal return line that goes through the tunnel sprunk a leak. It had a 3/8" line on it, and I replaced it with another 3/8" line, but the new one wont stay on and keeps slipping off. It looks like the new one is a little bigger inner diameter than the old one, and in some research I have found I need to get metric sized lines, but I cannot find the correct size anywhere in my searches.

Anyone happen to know?

Thanks!

[BoxsterGT]

The original was likely 7.0mm ID; current replacements today are 7.5mm ID and our host has this in stock. 3/8" (0.375") is definitely too big.

Len

[HawgRyder]

5/16"...?
will be a tight fit before clamping.
Bob

[BoxsterGT]

Since Porsche built this vehicle in Germany, Metric hose & fittings were used in it's construction. In 72, its likely the steel tube through the tunnel was 8.0mm OD, so the 7.5mm hose would be correct. The next larger tube used was 10mm OD, so the 9.5mm hose would be correct. These are still the standard Metric sizes used today.

5/16 is the closest inch hose to 7.5mm, and 3/8 is the closest to 9.5mm.

Len