Just realized that everyone is focused on the engine bay, but it's really accumulated heat energy that matters.  If the gas in the tank gets warm, then that extra heat energy in the engine bay will have more impact.  Low fuel level probably "locks" faster than a full tank.  Heat from the road will radiate up and and transfer to anything moving over it, even at high speed.  I wonder if insulating everything, including the tank, from back to front would help.  Even just a good shield between the tank and muffler might help.  Many of those shields get lost or removed.  Lowered cars might have more problem than standard height, from both radiative heat and lower air flow.  If I had the problem, I'd insulate everything I could find.

Here's a good picture of insulating the fuel lines from the thread "Nice '73 on BAT"

I think all that insulation on the fuel rail is keeping the heat IN. The early fuel rails are bolted to the head in three places, the heat travels up those contact points and heats the hardline, insulating that just keeps it in, not to mention the 4' of travel around a hot engine bay once the tube emerges from the tranny tunnel then another 4' to travel back. I say bring the fuel line across the firewall to the D/S of the tranny tunnel then dead head it straight into the carbs with no return. I ran mine like that with no problems.

Three heat sources are there - conductive (what you're talking about above), radiative (anything hotter than the fuel line will radiate heat across space to the colder object), and convective (hot air blowing over colder objects and losing heat energy).  They're all in play and hard to tell which way the heat is going, in or out, or which one is more powerful.  I feel nerdy now...

At the other end of the circuit, the return line in to the tank, the fuel is bringing heat back from the engine bay.  The tank contents warm up over time.  Could be that deadhead systems don't benefit from insulation and return systems do.  Or the size of that orifice is  critical for more than just pressure.  Cool fuel.  Didn't someone mention insulating the mounting points of the fuel rails, somewhere back in this thread or another.  That could remove the conductive path.

Interesting topic.  I've put lots of thought in to the EFI analog.  I have insulation for both convective and radiative heat sources, heat from the exhaust manifold, but left the rail (aluminum) uninsulated so that it could lose heat from the injectors.  The convective effect seemed to be pretty large, lots of heat coming up from the hole in the center of my exhaust heat shields.  Tiny hole, lots of channeled hot air.

How about a radiator for the fuel?  

Route it through the heater core.

Me thinks your staples are too tight...

12 minutes ago, Patcon said:

Me thinks your staples are too tight...

I told them to bring it in tighter, I'm almost 50 and got carded a month or so ago. Turns out the girl just started and was in training, but I was happy for a few days. 8^)

Haha!! So you were thinking you could use tighter staples as a country facelift? Nice!!  

any OEM fuel rail replacement substitution available? Any kit that comes with AN1 hoses?

On ‎09‎/‎06‎/‎2016 at 0:59 PM, Jeff G 78 said:

After struggling with heat related issues while racing for several years, I finally ditched the steel OE fuel rail and the problem was solved.  I had tried every type of heat shielding with no luck.  In the end, I believe that the heat was coming through the steel rail mounts and into the rail.  The insulation on the rail did a great job of holding the heat in.  Once I went to an all-rubber supply, I have no issues.

Jeff and Siteunseen,

After getting caught on traffic, couple of traffic lights and other stops, the car idle started to drop randomly from 900  to 200 rpm, however it never stalled. This means the heat shields i installed are helping get the heat out as its avoiding the fuel to evaporate at the fuel bowls. I parked the car and opened the engine door so heat started to get out. i took one picture of the fuel filter once i opened the engine bay and took another one after a couple of minutes running the car parked in idle. the rpm started to become stable at 800 to 900 rpm and did not dropped. So i think i still need to move forward and swap the metal fuel line with a modern approach rubber hose. I would like your opinión on this. I want to feel secure if i get stuck in traffic and tackle this issue which is surely VAPOR LOCK and nothing else! I even took out all the spark plugs and they were all fouled. I will not drive the car with the front Hood open, there must be a solution to get the heat out at traffic jams.

Edited October 5, 20168 yr by jalexquijano

 All the plugs were fouled? I fail to see how fuel starvation (vapor lock) can foul plugs. If the definition of fouled is oily, black, sooty, etc. 

Sounds more like percolation, I think.  Basically, fuel getting too hot in the carbs and forcing/finding its way out unmetered, adding extra fuel, I believe.  Still heat-related, so the rubber lines Jeff G described should help.  Progress!

It's been discussed before, part of the saga.  Might even be in previous pages of this thread.  Here's Nissan's take on it. - http://xenonzcar.com/s30/files/1973 240z 1974 260z fuel system modifications.pdf

That document is on the CZCC site also - 

 

Edited October 11, 20168 yr by Zed Head