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  1. #11
    Join Date
    Sep 2010
    Location
    Nova Scotia
    Posts
    795
    You may see some of your comments/ suggestions in my post below, so T-Y Kevin and others.

    Yesterday, I did a lot of driving, some of which was stop-and-go. Although it was very hot out (about 32 degC), it wasn’t as hot as the day I had the trouble that initiated this thread.

    Nevertheless, I took my temperature gun along for the ride and checked some under hood temperatures… an attempt at thermal mapping I suppose.

    The engine temp according the dash gauge reached the normal 180 degF and only went a little over driving around town. Here’s the results:

    Carb Float Bowls: 105 to 120 degF

    Fuel Log: similar to above; maybe a couple of degrees higher

    Radiator Expansion Tank: 180 degF

    Intake Manifold: 179 degF

    Fuel Line: 155 to 180 degF

    Fuel Pump: 180 degF

    Basically, if percolation is occurring, it appears that the fuel pump and fuel lines are most prone. The figure of 140 degF has been quoted as a vaporization point for gasoline, although there also appears to be quite a range.

    If you look at the picture below, (yes, my engine needs some detailing… I’ve been lazy about that) you can see my fuel line is copper. It starts at the fuel pump located on the left side of the engine, rises up, travels along behind the expansion tank bracket (where it’s ty-wrapped to the expansion tank support) and then heads aft towards the fuel log.

    Looking up the thermal conductivity of metals, I found that copper has a “k” of 401 and steel is 43 with SS being 16.

    Based on this, I intend to replace the fuel line with a steel insulated line as a first attempt at a cure.

    The carb float bowls never really became hot, so at this time I’m not intending to add spacers. As they are, there is an aluminum spacer under each carb separated by gaskets, and one of the gaskets is at least 3/16” think if I remember correctly.

    As the problem has only occurred when the engine temperature has risen considerably, I will investigate a larger electric fan for the radiator.

    Changing to a remotely mounted electric fuel pump with a return line is also an option, however that would be last on my list for a variety of reasons: cost and modifying the tank for a return line, being the major issues.

    During my internet investigation, I did discover that gasoline as different formulas for summer use vs. winter use and there has been some who claim that winter fuel is more prone to percolation in the summer.

    I don’t know if that’s true,, but I admit when this problem occurred, the fuel in thank was purchased last October. I have since filled up in July and havn’t had the problem since. I’m more inclined to think that that’s because the weather hasn’t been as hot, but I’m not sure. So many variable…..

    Last edited by Eggbert; 11-08-18 at 12:39 PM.
    John

    “A prudent person profits from personal experience, a wise one from the experience of others.”

  2. #12
    Join Date
    Feb 2007
    Location
    West Sussex
    Posts
    8,505
    cant see a pic, but agree -copper has excellent thermal heat transfer properties, so exactly the opposite of what's needed to avoid it getting hot.
    S/S is your best option.
    Crendon Chassis No.49
    Huddart FE428 + toploader

    Not listed in the Shelby Register.

  3. #13
    Join Date
    Sep 2010
    Location
    Nova Scotia
    Posts
    795
    Quote Originally Posted by KevinW View Post
    cant see a pic, but agree -copper has excellent thermal heat transfer properties, so exactly the opposite of what's needed to avoid it getting hot.
    S/S is your best option.
    That's odd. Here's a direct link:

    https://i.imgur.com/NX4gn1k.jpg
    John

    “A prudent person profits from personal experience, a wise one from the experience of others.”

  4. #14
    Join Date
    Sep 2010
    Location
    Nova Scotia
    Posts
    795
    I have just completed my first step in solving the boiling fuel issue. I swapped out my un-insulated copper fuel line with an insulated steel line.

    Instead of purchasing steel fuel line, I bought a length of brake line that had a coating on it to prevent corrosion. I thought this might help a bit for insulation. It was already flared at each end, so I cut off one end and removed the fittings.

    My old brake line used compression fittings with brass ferrules. This time I am going with a flared line so I had to change the fuel pump output fitting and the fuel log input fitting. I used Teflon pipe dope to help seal the threads.

    I slid on one fitting down to the remaining flare and connected it to the fuel pump. Through many removals and installations, I managed to make all the bends needed. I used a hand tubing bender to avoid kinks.

    Next up was to install my insulation. I thought I'd try some sort of rubber or plastic hose and ended up with silicon hose (approx. twice the temp rating of vinyl). It's a 3/8" O.D steel line and won't slide over 3/8" steel line. Friction stops everything with it pushed on about 2". So I went with silicone tubing with an I.D. of 10 mm. Was an easy slip fit, however going around the first bend wasn't easy. I then sprayed the line and down the hose with silicone lubricant and it went on easily.

    One nice thing about the silicone tubing is that it can compress a bit, so it was easy to push back to leave room for the fitting and the flare tool vice/clamp.

    Incidentally, a double flare is difficult with steel tubing, but with the addition of a C-clamp on the vice and some grease around the forming disk and screw tool tip, it did work.

    All installed, I waited overnight to test it out. Flashed it this morning and no leaks! I'll check again after a road test. Wiping around the fittings with a paper towel would reveal any weeping.

    So.... what next? A test drive at slow speeds on a very hot day. Not so likely as we seem to have come to the end of our weather. Sometimes we do get some hot weather in September. It's wait and see for now.

    Here's a picture. Careful readers will see the ignition wires are now under the line vs. over it as shown in the old picture with the copper line. No doubt I'll route them over the line next time I have the plug wires off.

    John

    “A prudent person profits from personal experience, a wise one from the experience of others.”

  5. #15
    Join Date
    Jan 2005
    Location
    leatherhead,surrey
    Posts
    979
    hi john,
    its just an observation, but the heater feed hose (?) running directly under the fuel feed, and the radiator expansion tank (right of picture) right next to the fuel pipe, wont help matters .
    -could these be wrapped in thin insulation/foam material(in close proximity to the fuel pipe) to prevent heat radiating into the metal fuel pipe?
    could this be part of the problem
    neil

  6. #16
    Join Date
    Feb 2007
    Location
    West Sussex
    Posts
    8,505
    Hi John, got a suspision I may be copying you at some point!
    Crendon Chassis No.49
    Huddart FE428 + toploader

    Not listed in the Shelby Register.

  7. #17
    Join Date
    Sep 2010
    Location
    Nova Scotia
    Posts
    795
    Quote Originally Posted by neil still building it View Post
    hi john,
    its just an observation, but the heater feed hose (?) running directly under the fuel feed, and the radiator expansion tank (right of picture) right next to the fuel pipe, wont help matters .
    -could these be wrapped in thin insulation/foam material(in close proximity to the fuel pipe) to prevent heat radiating into the metal fuel pipe?
    could this be part of the problem
    neil
    No doubt you are right, but as the problem occurred infrequently, only when the weather was extraordinarily hot, and that was with bare copper tube, I have high hopes I'll be OK now.

    Quote Originally Posted by KevinW View Post
    Hi John, got a suspicion I may be copying you at some point!
    Before you do that, I hope to confirm it works OK.... I'll report back if the weather cooperates. It's quite a pain to get all the bends right so if the silicone tubing fails, cracks or drips off, then I better report that too!
    John

    “A prudent person profits from personal experience, a wise one from the experience of others.”

  8. #18
    Join Date
    Sep 2010
    Location
    Nova Scotia
    Posts
    795
    So far the weather has not been all that hot so I don't know if my new insulated fuel line will cure the low-speed cruising issue or not. However, it has already shown one unexpected benefit.

    If I shut my engine off for a short while (10 to 20 minutes) or leave it overnight, it always starts right up. However if I try to start it 1.5 to 2 hours later, heat soak has heated the carbs and it takes 8 to 10 seconds of cranking (usually not all at once to give the starter motor a break).

    This scenario occurred the other day and the engine only had to crank 2 to 3 seconds before starting. I assume the fuel in the insulated line quickly got the carbs under control vs. boiling fuel vapour back when I had the un-insulated copper line.
    John

    “A prudent person profits from personal experience, a wise one from the experience of others.”

  9. #19
    Join Date
    Feb 2007
    Location
    West Sussex
    Posts
    8,505
    - I guess this is wy I have seen a lot of cars with their bonnets propped open on a hot day?
    Crendon Chassis No.49
    Huddart FE428 + toploader

    Not listed in the Shelby Register.

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