440 adding a vapor return line?

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When plumbing fuel on vehicles, I try to adhere to the NHRA rule book. It says no more than 12" of rubber fuel hose,unless that's been changed. Been a long time since I have built an NHRA legal car.

Not only will you get teched out of the track if you use more than that, but it's not a good idea to use a lot of rubber in the fuel system for a few reasons.

I know there's rubber fuel hose out there that can do the job, but then you're spending more money than on steel line. I don't even think about aluminum. No way no how. A lot of people run it, but steel is my personal preference.

It's cheap. Get you a good tubing bender (also cheap) and practice. You'll find it's a lot easier than you think and the results will look SO much nicer than some stupid rubber hose.
 
Or you call a supplier of quality pre-bent lines and get the exact piece for your car at a very reasonable price , then modify the ends to suit the different path of the return line . As Rusty said stay away from substituting rubber , in the late seventies early eighties Furd ran plastic lines on the Capri Coupes , a gravel road with a swale left my buddy walking home and a large puddle of raw fuel under his Crapi . Some lessons have to be learned hard by some people !
 
Couldna said it better. The only reason I didn't bring up pre-bent line is because sometimes it;s not available for everything........that and the fact that even if it is I will STILL make my own. LOL

cannucky said:
Or you call a supplier of quality pre-bent lines and get the exact piece for your car at a very reasonable price , then modify the ends to suit the different path of the return line . As Rusty said stay away from substituting rubber , in the late seventies early eighties Furd ran plastic lines on the Capri Coupes , a gravel road with a swale left my buddy walking home and a large puddle of raw fuel under his Crapi . Some lessons have to be learned hard by some people !
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ok so I went to the track yesterday it was hot...along the way the car ran good for about 15 miles temp 190.. in traffic temp got to 195 car dies, 850 dp holley mech fuel pump return line to the tank...pop the hood no fuel press...hold it to the floor it starts runs another 6 miles to the track gate dies again...did the same thing..held to the floor started got me in...when the sun went down, drove all the way home very little issues.. thoughts ideas.... the intake still has the exhaust dross over under the carb non blocked..alum rad hood scoop..air movement under the hood seem good...
 
Forget which carburetor you have. Does it have the thick insulator gasket under it? Almost sounds like fuel is boiling in the carburetor, or vapor locking elsewhere in the fuel line. How is the supply fuel line run? Is it close to something that gets very hot?

People have had to insulate mechanical fuel pumps in the past, because they get heat transfer from the engine and boil the fuel. Mechanical fuel pumps cannot pump vapor if that's the case.

All that said, real honest to goodness vapor lock is pretty rare.
 
thanks for the reply, 850 dp holley.. eddy intake with the heat crossover not blocked under the carb..recently added a return to the tank with the wix filter,,, if my return is working will I have pressuer on the fuel gauge at the carb after I shut it off...and when it does die, there is no pressure on the gauge...I can hold it to the floor it will start and run fine
 
flathead31coupe said:
thanks for the reply, 850 dp holley.. eddy intake with the heat crossover not blocked under the carb..recently added a return to the tank with the wix filter,,, if my return is working will I have pressuer on the fuel gauge at the carb after I shut it off...and when it does die, there is no pressure on the gauge...I can hold it to the floor it will start and run fine
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How is your fuel return plumbed? Does the fuel flow through the carb bowls and then back to the tank or do you just have the return in parallel with the carb? If it's the second choice the fuel is just sitting in your carb until it gets used by the engine thus giving it a chance to heat up. Also definitely look into a carb spacer made out of either wood fiber or phenolic (plastic) at least 1/2" thick, and finally unless you drive your 440 in the winter go ahead and block off that exhaust crossover.

I swear every year pump gas gets sh!ttier, in a few years it'll boil off at room temp and 91 will ping like 75-octane:wtf:
 
MOPEkidD-3 said:
How is your fuel return plumbed? Does the fuel flow through the carb bowls and then back to the tank or do you just have the return in parallel with the carb? If it's the second choice the fuel is just sitting in your carb until it gets used by the engine thus giving it a chance to heat up. Also definitely look into a carb spacer made out of either wood fiber or phenolic (plastic) at least 1/2" thick, and finally unless you drive your 440 in the winter go ahead and block off that exhaust crossover.

I swear every year pump gas gets sh!ttier, in a few years it'll boil off at room temp and 91 will ping like 75-octane:wtf:
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what do you mean flow through the carb ? do you have a pic or drawing
 
flathead31coupe said:
thanks for the reply, 850 dp holley.. eddy intake with the heat crossover not blocked under the carb..recently added a return to the tank with the wix filter,,, if my return is working will I have pressuer on the fuel gauge at the carb after I shut it off...and when it does die, there is no pressure on the gauge...I can hold it to the floor it will start and run fine
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The Wix WILL relieve pressure on key shutdown. This is a GOOD thing because it prevents pressure build which can force more fuel past the needles/ seats and cause fuel to run over into the manifold.

On the same not what might be happening, is that the fuel in the carb might be boiling and flooding over into the manifold. Use a sandwich heat spacer and run your float levels on the "low" side. Bear in mind that float level can creep so check it a couple of times........HOT
 
ok after installing the wix filter the right way it seems to work went for a drive no issues...other the the press gauge bounces around when at idle
 
The way the mechanical pump works is to receive a swat from the eccentric bolted on to the front of the cam,which happens every second revolution. Then the pump tries to move a little fuel up the line. At idle, only a tiny bit will enter the float bowl. The rest will head back to the tank via the return line. If the WIX filter has a checkvalve in it or a fixed orifice, then there will be a brief pressure spike until the pressure equalizes as the fuel passes thru it. The fluctuating gauge is just reflecting what is happening.
 
AJ/FormS said:
The way the mechanical pump works is to receive a swat from the eccentric bolted on to the front of the cam,which happens every second revolution. Then the pump tries to move a little fuel up the line. At idle, only a tiny bit will enter the float bowl. The rest will head back to the tank via the return line. If the WIX filter has a checkvalve in it or a fixed orifice, then there will be a brief pressure spike until the pressure equalizes as the fuel passes thru it. The fluctuating gauge is just reflecting what is happening.
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cool thanks
 
I bet you knew that, eh?
But consider that the fuel pump is sucking. If you've ever watched a pump suck thru a clear line you will see some amazing stuff. Any little sharp protrusion will cause little bubbles to form, just like coke bubbles in a plastic tumbler. And if there is any tiny air leak into the line, the pump will pull air in rather than fuel cuz it's all uphill from the tank, and it's just easier to pull air than it is to lift fuel.
They say that gas boils in the carb, and I guess that would be true, but as long as there is solid fuel and fuel pressure between the pump and the float valves, the fuel should not boil in the line. This is why I do not have a filter between the pump and the carb, they collect air, and become a mini surge tank.
But where does the pressure go while driving?
Well it would seem obvious, that if you get a restart with the gas-pedal on the floor, that the engine was probably flooded.If these two happen simultaneously while driving, you have to point the finger at the float valves. They are not controlling the fuel.
But one might think, perhaps the line is full of air, and the valves cannot control air. Well that's just not true; I check those valves all the time using regulated air pressure.
What is true tho, is that if air is being entrained somewhere in the system, the pump will pile it up on the pressure side for as long as it can. Then eventually the float bowl goes dry and the engine stalls.As soon as that happens, all the air on the suction side rises to the highest point,probably back at the tank. Of course that means all the fuel piles up at the lowest point. Now with a bit of cranking, the pump gets some solid fuel and fills the bowl again, and away you go. For a little bit, until the cycle repeats.
Another thing that can happen between the pump and the carb, with intermittently leaking float valves, is whenever the pressure drops, hot fuel can instantly flash to vapor. This vapor will go out thru the bowl vent, and the line begins to empty out. Of course the pump would continue to pump fuel, for as long as the engine continues to run. So then you hop out and check that stupid semi-transparent filter and see that it's full of air. Seeing that and no fuel pressure might lead you to think that the pump has died. But really it's just the valves, or at least one of them if a dual feed.
Now if you install a return line, most of the air will get pumped back to the tank, and the load on the valves will be eased at part throttle, so maybe the valves don't leak so much, and everything seems normal.
But it may not be...........
Some carb manufacturers offer float valves with different sizes of orifices. I wonder if you have one, or a set, of the large holed valves. These may not seal properly with a low-pressure street system. Just a thought.........
 
The Wix filters have no check, they are a simple orifice. It might be worth mentioning that mech pumps do NOT pump from cam action, exactly. The cam "cocks" them, it is actually the spring in the pump which moves fuel on the return stroke, and this is why they regulate pressure. The pressure is limited by the strength of that spring. When you are "light" using fuel, the pump arm can "float" on the cam, barely touching it if no fuel is needed, and the needles are closed. This is also why you can run a rear electric in series with the front pump and it won't increase pressure. The pressure with two pumps will be whatever the highest pressure one puts out.
 
67Dart273 said:
The Wix filters have no check, they are a simple orifice. It might be worth mentioning that mech pumps do NOT pump from cam action, exactly. The cam "cocks" them, it is actually the spring in the pump which moves fuel on the return stroke, and this is why they regulate pressure. The pressure is limited by the strength of that spring. When you are "light" using fuel, the pump arm can "float" on the cam, barely touching it if no fuel is needed, and the needles are closed. This is also why you can run a rear electric in series with the front pump and it won't increase pressure. The pressure with two pumps will be whatever the highest pressure one puts out.
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good point. no spring no pump
 
Always ran both electric and HV mechanical pumps in series back in the day. Holley blue installed at rear frame rail. Car in North Florida (Blanding Blvd) never failed to vapor lock. All my lines were increased to 3/8 or larger. I installed a Moroso cool can and as long as I dropped some ice in prior to making the trip, either home to Orange Park or to Pecan Park dragtsrip it never had an issue. Never noticed a drop on the gauge, the damn thing would just boil up. Always thought a return line would help keep the fuel cooler. Just difficult to run a hard line back to the tank if you are using a stock tank configuration. I certainly would run a hard line though.
 
First car I ever had or saw with a return system was my 70 440-6. AND IT WORKED. I know because for some reason I removed it......................................................I remember........

Had an electronic pump I can NOT remember the name of, and it never shut off. Turns out that was design. I thought the return was the problem and pulled it off LOL. First few hot days (I was stationed in San Diego at NAS Miramar then) it would lock

Here we go but I don't remember this brand and mine was not blue........might have been sold under different name, but this is "the" pump..

Conelec3.jpg
 
67Dart273 said:
First car I ever had or saw with a return system was my 70 440-6. AND IT WORKED. I know because for some reason I removed it......................................................I remember........

Had an electronic pump I can NOT remember the name of, and it never shut off. Turns out that was design. I thought the return was the problem and pulled it off LOL. First few hot days (I was stationed in San Diego at NAS Miramar then) it would lock
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With the aftermarket senders sold today with 3/8 outlet they come with the return fitting so if you get the hard line back to the tank even if 5/16 it has to be a plus!
 
67Dart273 said:
First car I ever had or saw with a return system was my 70 440-6. AND IT WORKED. I know because for some reason I removed it......................................................I remember........

Had an electronic pump I can NOT remember the name of, and it never shut off. Turns out that was design. I thought the return was the problem and pulled it off LOL. First few hot days (I was stationed in San Diego at NAS Miramar then) it would lock

Here we go but I don't remember this brand and mine was not blue........might have been sold under different name, but this is "the" pump..
Click to expand...

So random question here that's sort-of related, why did only the HP engines (440-6, 426 Hemi) get the vapor return setup? Did they simply produce more underhood heat because of their performance nature or was there more to it than that?

I know that changed later, my '88 Chrysler 5th Avenue has a vapor return fuel filter from the factory and that's just a 318 2-bbl.
 
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