 Fuel lines and twin carbs |
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| JFG |
 May 22 2016, 09:41 AM
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#1
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Senior Member  Group: Members Posts: 686 Joined: 7-April 16 From: Wales Member No.: 19,869 Region Association: None  |
I am fitting twin IDF 40's to my 1.7 engine (it came as a rolling shell) and need to change the fuel lines from front to back.
Do I need to install a return line? What size outside and\or internal diameter are the standard lines? I'm going to make my own using stainless steel and need the specs to buy the correct pipes. Finally. Do I need to tap a vacuum take off into the manifolds for the distributor? |
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| Dave_Darling |
May 22 2016, 11:41 AM
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914 Idiot Group: Members Posts: 14,981 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California 
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Some pumps do not require a return line. Some do. So it depends entirely on your choice of fuel pumps. If everything is apart, I recommend installing the return line regardless. If you don't need it, you can cap it off or just ignore it. Much easier to do that than to install the line after half the car is together.
The supply line is ~9mm OD. The return line is ~7mm OD. Far, far easier to get the lines pre-bent from Tangerine Racing. Tapping the carbs for vacuum advance is not necessary. It may help things, depending on how you set everything up, but it might not. --DD |
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| HansJan |
May 26 2016, 08:27 PM
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#3
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Member Group: Members Posts: 394 Joined: 5-April 16 From: Sugar Land TX Member No.: 19,860 Region Association: Southwest Region
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I installed the supply line from Chris (Tangerine). Very easy operation. Only if I were a very good tube fitter (like hydraulics tech) I would make my own. The pump in my car is in the rear, and does not require a return line. Its an EMPI-pump with dual carberator setup.
If you decide to make your own I suggest that you use tubing as much as possible (using crimp-fitting if needed) and reduce rubber hose as much as you can. Good luck Hans Jan |
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| stugray |
May 26 2016, 10:27 PM
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#4
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Advanced Member Group: Members Posts: 3,824 Joined: 17-September 09 From: Longmont, CO Member No.: 10,819 Region Association: None |
Install them both.
If you decide to not use the second tube, use it as a conduit to run wires from the back to the front under the tank for the best pump location. I run a Holley redtop in the front with an adjustable pressure regulator (non-return style) in the rear above where my relay board used to be. It goes to the driver's side carb IN, then the OUT goes over to the pass side carb. The holley is loud and overkill. I have heard that carters are just as good quality & longevity wise, but cost less and quieter. Many get by with a non-regulated facet pump. |
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| brant |
May 27 2016, 08:39 AM
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#5
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914 Wizard Group: Members Posts: 11,613 Joined: 30-December 02 From: Colorado Member No.: 47 Region Association: Rocky Mountains 
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All manufactures use return lines
Cooler circulatory fuel |
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| JFG |
May 27 2016, 02:04 PM
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#6
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Senior Member Group: Members Posts: 686 Joined: 7-April 16 From: Wales Member No.: 19,869 Region Association: None |
5 years sine I last owned an air-cooled, I'm surprised by how much I've forgotten and how many basic errors I'm making. Didn't even remember the fuel flow reg!
Thanks for the help. |
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