[Roadsters] Fuel line thingie

[John F Sandhoff]

I believe the fuel line widget that's being discussed is part of
the anti-vapor-lock system. It is a thermostatic (heat controlled)
valve that mounts near the rear of the engine, and has an inlet fuel
line coming from the carb and an outlet fuel line that returns to the
tank. It is not emissions and it is not a pressure regulator. It is 'a
good thing'.

Starting with '68, the distributor was recurved to run at 0 degrees
BTDC. This reduces emissions, destroys off-the-line performance,
and causes an idling engine to run hot (thus the extra vacuum
lines and valves and such to advance the dwell when the engine
starts to get critical). This extra heat exacerbates a problem with
carbureted cars: vapor lock. Hot gasoline wants to vaporize (boil)
in the fuel lines, and when that happens it prevents the flow of liquid
gasoline to the carbs.

So: the thermostatic fuel control valve. This widget is normally closed
(or close to it). When things heat up, an internal valve opens and allows
a controlled amount of gasoline to return to the tank via the return line
(this line is unique to 68+ cars). It's a restricted flow so the carbs
still get gasoline, but it keeps the fuel moving so it stays cooler and
is less prone to boil and vapor lock.

There's your history lesson for the day...

-- John
     John F Sandhoff   sandhoff at csus.edu   Sacramento, CA

p.s. Fuel injected cars have a pressure regulator that also circulates
fuel, but that's a whole 'nother thing...