Pure gasoline vaporizes at 140 degrees, BUT ethanol is more like 174 degrees, so the gas we all use being 10% ethanol is going to in theory have a slightly higher point of vaporization, assuming a homogeneous mixture.

My concern would be exhaust heat.  My fuel line from the pump (engine mounted) to the carb runs right past the #2 header tube, but I've never had an issue with vapor lock, even when it was past 95 degrees outside.  The headers are ceramic coated, which means they radiate less heat that uncoated headers, and my fuel line is aluminum, which rejects heat much better than steel and steel alloys.  In  general though. try to keep it away from the exhaust and I think you'll be fine.  I would not for example run the fuel line along the vale cover above the header, as that exposes a considerable surface area to heat. 

As far as heat transferring through the clamps to the fuel line, I don't think I'd worry.  The clamps are aluminum, so they will tend to reject heat. 

Take a cast iron skillet and an aluminum frying pan and put them on the same heat.  Once at temperature remove them from the heat and check the temperature after 5 minutes, then 10.  You'll be able to handle the aluminum pan long before the cast iron skillet.

Heat rejection isn't about a metal's ability to be brought up to or hold temperature in the constant presence of heat.  If I put anything in an oven its going to become the temperature of the oven, and likewise, if I bolt anything to an engine its going to become the temperature of the engine.  But, when the heat isn't constant, or when there's air circulation, aluminum is going to reject heat better than any other common metal.  Note this isn't a questions of insulation, which would be preventing heat transfer.  I think this is where the confusion might lie.  

If you want insulation from heat you need something to reflect heat like foil faced wrap, or some form of insulation to prevent heat transfer like a phenolic.

If not to late...why not slip a piece of shrink tube over fuel line (inside clamp) to act as insulation/heat break or just a piece of rubber?
6s6

Aluminum is also the best metal for combating heat soak, which is why its used in heat sinks in electronics.  Often heat sinks have a means of air circulation used in conjunction (CPU fan, etc.), but not always.  When in motion I think you've got enough air circulation.  The potential problem is once you stop and the car sits, but at that point what the fuel line clamps are made from doesn't matter, because the engine bay has become an oven.  Its radiating and holding heat as much as its transmitting heat at that point.  So if the fuel line's going to get hot enough to vaporize the fuel its going to get hot enough from the radiant heat.  The clams could be phenolic at that point and the fuel's still going to vaporize.  In the end the way the line is routed is going to make a much larger difference than what the clamps are made from. 

In general, thinking about how every OEM setup was done that I can think of, fuel lines run through the engine bay for the shortest amount of distance possible.  As far as heat transmissions goes though, at some point the fuel line is connected to the engine.  The engine is hot, and is going to conduct heat into the fuel line.  Its also by no means uncommon for fuel lines to be clamped to the engine in one of more spots to aid routing.  This is typically done with steel or plastic clamps.  Depending on the plastic, in order of best possible choices I would rank them: plastic, aluminum, and steel in terms of preventing any heat related issues.  But plastic has its own problems, mostly that it gets brittle and fails. 

With a timing cover mounted fuel pump and front fed carb I've never had need to add clamps to the fuel line.  My setup has no rubber line in it.  Hard line from the carb to the filter, hard line from the filter to the pump.  Adapters used as needed.  Works great, even with aluminum line that is less rigid than steel. 

Last edited by TKOPerformance (10/31/2018 11:51 AM)

 I think that today's fuels are different than back in the day when my DD was  a  62 Mercury Meteor with a 221 Windsor, that's the last time I  had vapor lock.
Please raise your hands if you have  had vapor lock with modern gas.

The only thing I have experienced vaporlock in was my buddies Grumman van.  The fuel line was right next to the exhaust along the frame rail and would get cooked going over a mountain grade. Fixed it with a goofy insulation sock for the hard line.

For now I am going to leave the line the way it is, but put the clamps on a diet in the mill to make them a little less chunky, and set them off on some high temp rated fiberglass insulating board.  Future land might have a 100% hard line solution...