fuel boiling solutions

Fuel and Air Systems

  1. Sonny

    Sonny Well-Known Member

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    It’s 80 degrees now here in Florida and with it came fuel boiling issues for my new 440. Engine temp never exceeded 200, but at traffic lights my air fuel ratio slowly dropped to rich readings and with it came poor idle. After sitting 15 min and engine off, carb bowls are empty.

    I did this last year with my 360 with alum intake. Added wood spacer, blocked off exhaust risers, insulated lines, etc. but still had issues over 90 degress. I would prefer to actually fix it this time.

    I’d like to get some details from folks who have gone to an electric pump. I currently have a single 5/16” line, no return, from my sender to my 440. I bought a new sender with 3/8” supply and 1/4” return to install.

    This is a road trip/car show car so not worried about having a massive racing pump. I need a pump with about 15psi or so and can lift fuel out of the top of my stock tank (external pump). I’ll need to add a regulator too. So a few questions:
    -pump recommendations?
    -where did you mount the regulator?
    -did you use a relay for power to the pump?
    -did you run steel lines or other?
     
  2. Bad Sport

    Bad Sport FBBO Gold Member FBBO Gold Member

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    I had the same issues.

    I bought a standard draw through electric pump from NAPA and installed it in the line right by the tank.

    I turn it on via a covered toggle switch to get the gas up to the mechanical pump, once up and running I just turn the electric off.
     
  3. PurpleBeeper

    PurpleBeeper FBBO Gold Member FBBO Gold Member

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    Hey Sonny, I've been down this road before.
    1. I did this last year with my 360 with alum intake. Added wood spacer, blocked off exhaust risers, insulated lines --> All of this is still a good idea
    2. Blend you anti-freeze differently. More water = better cooling as long as you still have enough antifreeze not to freeze up at night. What anti-freeze are you using? Do you have iron or aluminum heads?
    3. I'm not sure an electric pump will help all that much & you don't need 15psi to get fuel out of the tank. The only advantage I can see is an electric pump in back not being bolted directly to a hot engine. I've had PLENTY of vapor lock (fuel boiling) issues using electric fuel pumps. You only need about 5-6 psi at the carburetor.
    4. Watch your fuel lines....you might want to wrap some header tubes in addition to the fuel line where they get close (passenger inner fender area)
    5. Sometimes timing can make an engine run hot....can't remember if it's too far advanced or retarded that can cause an issue (?)
    6. What is your cooling system? If you can keep the engine to a maximum 180F, that will help your issue too.
     
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    • PurpleBeeper

      PurpleBeeper FBBO Gold Member FBBO Gold Member

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      7. If all else fails, the fuel return line will likely help. I've been planning to add this to my car too, but haven't done it yet.
       
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      • Sonny

        Sonny Well-Known Member

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        Thanks PB. I have stock 452 iron heads, Edelbrock dual plane intake with exhaust ports blocked, and QF Brawler 650 carb. I have a 3/8” fuel hose slid over my 5/16” hard line inside the engine compartment as it passes the steel headers. I know my non ceramic headers aren’t helping matters either. I’m running Autozone brand 50/50 antifreeze. The temp here only gets close to 32 once a year if that. What ratio do I really need? 90/10 water/af? Stock 26” radiator and fan with heavy duty clutch, 180 degree high flow thermostat (could go to a 160 I guess).

        I was in the process of adding a fuel filter with a vapor breaker and a 1/4” line back to the tank, then thought if I’m going to all that trouble why not just go ahead with the pump? Sounds like the pump alone won’t solve the issue?
         
      • ChargerM440

        ChargerM440 Well-Known Member

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        The easiest way (that I have found) to adapt the delivery/return is to keep the 5/16" line thats on the car to use as a return and add a 3/8" or larger line to use as the feed to the engine. You can buy a pre-bent line and install it along side the existing line. This is what I have done.
         
        Last edited: Feb 11, 2019
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        • Dennis H

          Dennis H FBBO Gold Member FBBO Gold Member

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          Spacer, wrapping, electric pump. None resolved my issues. Hoping the efi is the answer. This season will tell. Ethanol boils at around 173 ish. Can’t get away from it in these parts.
           
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          • Bad Sport

            Bad Sport FBBO Gold Member FBBO Gold Member

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            The gas we get today is pure crap for an unsealed system. EFI should be a big help.

            I was having issues with my car, so I conducted a little experiment, I poured a bit of gas into a spray bomb lid about enough to just cover the round piece inside that covers the spray nozzle on the paint can.

            It was hot and humid here and was set to be for a few days, I set the cap on my workbench and came in the house for the day. I went out the next day (about 24 hours later) and the cap was bone dry.

            That 'gas' had completely evaporated in 24 hours.
             
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            • Sonny

              Sonny Well-Known Member

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              I think you speak the truth. My 318, then 360, and now 440 all boil fuel at about 195 engine temp. My 396 Impala was the same too without fail.
               
            • Sonny

              Sonny Well-Known Member

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              Maybe I’ll go back to ethanol free 87 gas and add octane boost?
               
            • danf_fl

              danf_fl Well-Known Member

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              Have you tried an "in-tank" fuel pump?

              I've heard the suggestion from an auto restorer in Florida. He stated that external electric fuel pumps get too hot.
               
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              • HT413

                HT413 Semi Pro Bowler

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                Before I went to EFI, I had the same issue on my 451. While checking around, I accidentally burnt myself on my carb. So there was my problem.

                Went for a 1” phenolic spacer, insulated the supply line, added a return with regulator and solved it. Carb was much cooler to the touch.

                My next step was going to be to fab a simple aluminum heat shield for between carb and intake.

                The reality is that no matter what we do, the fuel bowls will boil empty on a hot day with a hot engine when we shut it down for a while. But that’s not so much of an issue, the pump should fill them pretty quick.
                 
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                • Sonny

                  Sonny Well-Known Member

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                  . For me this issue is the poor idle and the engine trying to cut off in traffic because it’s too rich.
                   
                • 5.7 hemi

                  5.7 hemi FBBO Gold Member FBBO Gold Member

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                  A return line should solve most of the problem.
                   
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                  • WileERobby

                    WileERobby Well-Known Member

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                    Holley gerotor pump. It's a little expensive, but it's quieter than the usual blue or red pumps. Mount it near the tank and you troubles are over.
                     
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                    • Sonny

                      Sonny Well-Known Member

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                      Took the car out this week and the temp went to 205 after just 10 minutes and it was only 72 outside. Of course it started running rich. I had previously added a rubber spacer, Insulated my fuel lines and fuel filter, etc. based on earlier comments so it made it a little longer this time before it went down hill. I have yet to add the vapor separator line. Hope to install it this week.

                      Took a look in the radiator and it’s nearly 50% plugged! Guess there was some residual rust pebbles left in the block and there is also buildup in the cells. Went ahead and bought a 3 core Champion aluminum radiator, 160 degree high flow Mildon thermostat, and a high flow pump. That was the original 26” radiator. Guess it was time to retire it. This should significantly help keep the 440 under 200 degrees. I hope.
                       
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                      • furryfrog

                        furryfrog Well-Known Member

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                        I tried a bunch of similar things to prevent my carb fuel bowls from boiling over. The only thing that worked was a return line installed in the bottom of each bowl, teed together and gravity draining back to tank. I used a small office size, cant remember but something around a .020 drain hole for each bowl.
                         
                      • khryslerkid

                        khryslerkid FBBO Gold Member FBBO Gold Member

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                        And your antifreeze doesn't have to be 50/50. I would dilute it for around 0*F. Not sure what ratio that would be. Thats where mine test at. The more water the more it dissipates heat.
                         
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                        • Kern Dog

                          Kern Dog FBBO Gold Member FBBO Gold Member

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                          This cured my problem.
                          1970 Charger, 440/493 with 2" headers, Holley mechanical pump, 3/8" sender, 3/8" lines. The pump would usually stay around 5-7 psi until the weather warmed up, then it would fluctuate a lot.
                          I got tired of the fuel pressure dropping in warm weather. The fuel line was moved away from heat sources, covered in a fabric shield...it still would empty the filter and cause the car to sputter at higher rpms. I installed a Carter mechanical fuel pump but it ran at 11 psi !
                          I bought an Aeromotive regulator and plumbed it to a 1/4" return line. Now the fuel pressure stays around 4 at idle, raises up to 7 at higher rpms and the fuel stays in circulation...."a loop" so to speak. No more fuel pressure fluctuations, no empty filter and no sputter.
                          SCORE !
                           
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                          • Dana

                            Dana Active Member

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                            This E10 fuel is 50% vapor @170 degrees. All you need is a 30 dollar holley mighty mite electric pump, back by the tank. The smallest on they make, in conjunction with your mechanical pump.
                             
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