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> Dual Weber 40’s, Fuel lines
KevinW
post May 22 2020, 11:43 AM
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I am looking for a drawing or detail Or picture how to route the fuel lines. I have searched the web but no luck. I have an idea about the supply line but not sure about the return line?
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bbrock
post May 22 2020, 01:48 PM
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There is another reason to keep the return line. The reserve fuel system depends on it. In the pic below, you can see that the supply line drains from a bowl in the bottom of the tank and the return dumps fuel back in it. This allows the system to constantly scavenge fuel from the tank and concentrate it in that bowl so you can use all of the fuel before sucking air. I've read of people complaining that their car was running out of gas with the gauge showing 1/8 or more of a tank after switching to carbs. I'm guess this is why.

(IMG:http://www.914world.com/bbs2/uploads/post-20845-1587959064_thumb.jpg)
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Superhawk996
post May 22 2020, 02:05 PM
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QUOTE(bbrock @ May 22 2020, 03:48 PM) *

There is another reason to keep the return line. The reserve fuel system depends on it. In the pic below, you can see that the supply line drains from a bowl in the bottom of the tank and the return dumps fuel back in it. This allows the system to constantly scavenge fuel from the tank and concentrate it in that bowl so you can use all of the fuel before sucking air. I've read of people complaining that their car was running out of gas with the gauge showing 1/8 or more of a tank after switching to carbs. I'm guess this is why.

(IMG:http://www.914world.com/bbs2/uploads/post-20845-1587959064_thumb.jpg)


Good point but not entirely correct. You can run them dry without a return line. Ask me how I know. (IMG:style_emoticons/default/laugh.gif)

Fuel will still enter the "coffee can" as low fuel sloshes to and fro. You'll notice the holes in/out of the coffe can are quite small. So they effectively act as an orifice to restrict flow out of the can concentrating fuel around the pickup inlet. Also the inlet is situated at the low point and all other sufaces slope toward the coffee can to try to feed it.

In my case I did get episodes of running then stalling that came a mile or so in advance of when I had to walk to the gas station so I'll readily concede that a return line may have helped prvent that. But at the end of the trip, when the gas is gone, your walking. (IMG:style_emoticons/default/sad.gif)

I'm wondering if those with the 1/8 tank scenario were running around with debris plugging the coffee can in/out orifice holes.

Fully concur that return line is the modern, proper solution that will help cool fuel and reduce vapor lock. I did what I did (not using return) before I knew any better.
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bbrock
post May 22 2020, 03:27 PM
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QUOTE(Superhawk996 @ May 22 2020, 02:05 PM) *

I'm wondering if those with the 1/8 tank scenario were running around with debris plugging the coffee can in/out orifice holes.


I just assumed the engine was being starved when they cornered. Obviously if the car is running level you would be able to run them dry because I don't think the supply/return tubes make a liquid tight seal with the can, but that isn't how we are supposed to drive these cars. (IMG:style_emoticons/default/biggrin.gif) I would prefer to have my last quart of fuel in that bowl rather than sloshed up against the far end of the tank. Also, with the orifice holes half way up the sides of the can, I'm not sure how much fuel would wind up sloshing into the can when the tank gets low.

I also ran a 914 and a bus on carbs without return lines. I really can't remember if there were any issues with stuttering as the tanks got low. Didn't do a lot of hard cornering in the bus though as I had an annoying habit of not wanting to tip it over. (IMG:style_emoticons/default/laugh.gif)
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Superhawk996
post May 22 2020, 03:48 PM
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QUOTE(bbrock @ May 22 2020, 05:27 PM) *

QUOTE(Superhawk996 @ May 22 2020, 02:05 PM) *

I'm wondering if those with the 1/8 tank scenario were running around with debris plugging the coffee can in/out orifice holes.


I just assumed the engine was being starved when they cornered. Obviously if the car is running level you would be able to run them dry because I don't think the supply/return tubes make a liquid tight seal with the can, but that isn't how we are supposed to drive these cars. (IMG:style_emoticons/default/biggrin.gif) I would prefer to have my last quart of fuel in that bowl rather than sloshed up against the far end of the tank. Also, with the orifice holes half way up the sides of the can, I'm not sure how much fuel would wind up sloshing into the can when the tank gets low.

I also ran a 914 and a bus on carbs without return lines. I really can't remember if there were any issues with stuttering as the tanks got low. Didn't do a lot of hard cornering in the bus though as I had an annoying habit of not wanting to tip it over. (IMG:style_emoticons/default/laugh.gif)


I'll have to look at my tank closer again to see where my coffee can orifice holes are, I think there are two or four much smaller holes down by the bottom of the coffee can.

I don't recall having any gas left at all when I looked in the tank but I also didn't have a good bright flashlight looking in there. That was the era of dim bulb 2AA cell Mag light in glovebox and I was looking though the filler hole itself so can't see as much as you've shown in the photo when you can pull the whole filler assembly.

Granted I wasn't cornering like an AX or track situation when I ran out but I was on curvy roads (North Michigan remember, not CA canyon roads). I got some sputtering in the corners (long below 1/8 tank), slowed down when I looked at the guage and realized how screwed I was. I then tried to limp it at 40-45 mph into town. Almost made it. (IMG:style_emoticons/default/av-943.gif)

Now I'm super curious!
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bbrock
post May 22 2020, 04:06 PM
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QUOTE(Superhawk996 @ May 22 2020, 03:48 PM) *

Now I'm super curious!


The contraption looks very ingenious to me (clever Germans). It looks like the can is designed to be leaky so it can fill from the tank but drain a little slower than it gets refilled by the return pump. The result being that as the tank gets low, there is a little can full of fuel not sloshing around too much to keep the supply tube submerged. Seems pretty nifty.
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Posts in this topic
KevinW   Dual Weber 40’s   May 22 2020, 11:43 AM
brant   this has been a controversial topic for ever... a ...   May 22 2020, 01:29 PM
bbrock   There is another reason to keep the return line. ...   May 22 2020, 01:48 PM
Superhawk996   There is another reason to keep the return line. ...   May 22 2020, 02:05 PM
bbrock   I'm wondering if those with the 1/8 tank scen...   May 22 2020, 03:27 PM
Superhawk996   I'm wondering if those with the 1/8 tank sce...   May 22 2020, 03:48 PM
bbrock   Now I'm super curious! The contraption ...   May 22 2020, 04:06 PM
SKL1   That makes sense but I've been running carbs o...   May 22 2020, 02:06 PM
ChrisFoley   I have never used a return line on a carbed car an...   May 22 2020, 05:20 PM
IronHillRestorations   I'm with Chris on this. I've never run a ...   May 22 2020, 06:14 PM
KevinW   I will be using a Facet fuel pump. When not using ...   May 22 2020, 06:34 PM
ChrisFoley   I will be using a Facet fuel pump. When not using...   May 23 2020, 09:58 AM
bbrock   You can also get a bypass regulator that can be c...   May 22 2020, 06:47 PM
SirAndy   Facet pumps will drive you batty with the noise. ...   May 22 2020, 08:09 PM
mtndawg   Facet pumps will drive you batty with the noise. ...   May 22 2020, 10:25 PM
ndfrigi   [quote name='bbrock' post='2818051' date='May 22...   May 23 2020, 01:23 AM
mtndawg   [quote name='mtndawg' post='2818099' date='May 22...   May 23 2020, 01:19 PM
ndfrigi   [quote name='mtndawg' post='2818099' date='May 2...   May 23 2020, 02:10 PM
Ansbacher   The inventor of the Facet type pump is now sitting...   May 23 2020, 11:24 AM
IronHillRestorations   I may have been talking through my hat. There use...   May 23 2020, 12:13 PM
KevinW   Thank you everyone for the advice   May 23 2020, 04:40 PM


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