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'72 Opel GT (Sara)
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Discussion Starter #1 (Edited)
This past summer was my first full summer with the GT in over a decade :banana: and I drove it a lot on the very hottest of days here in Atlanta. Often, I would find my fuel filter completely empty with the traditional "stock" routing of the fuel lines in front of the engine block. As a result, over the past few months I have experimented with many different routes for the fuel lines and filter from the fuel pump to the carb in an effort to combat heat issues. The one I document here has proven for me to be both the best for keeping the fuel flowing as well as the most aesthetic since the fuel line is practically invisible. I thought I would share as others may want to try this.

Using 5/16" ID rubber fuel line (you will need ~4.5' of it in total), route the fuel line from the pump up to the bracket that holds the hood release rod and use a zip tie to attach it there (see photo 1 - the zip tie can be seen just under the #2 spark plug wire). Next, you will get double duty out of the clips that hold the firewall material in place to route the fuel line back along the firewall and over the valve cover (but hidden from site for a nice clean look). See photos 2 and 3 where I have used zip ties to attach the fuel line to the back of the firewall keeping it behind the hood latches. Note how the fuel line goes over the valve cover but does NOT touch it. The name of the game here is to keep the fuel line from touching anything hot and maximizing air flow around it. Next, insert an in-line fuel filter such that it can be positioned in the far back corner (passenger side) of the engine bay and up high (see photo 4). Make certain that the fuel filter is not touching the metal back there - you don't want vibrations and such rattling that glass fuel filter around. Mine is held firmly in place again by making use of a zip tie and a nearby firewall clip. Finally, finish the route by connecting the output side of the fuel filter directly to the carb (see photo 5). With this arrangement, my fuel filter stays chock full of fuel often times not even having an air bubble in there.
 

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One small suggestion . . .

. . . nice job and generally well thought out . . . except that your fuel filter is located in what is perhaps the GT's hottest underhood spot!

Forced hot air drawn from the radiator and radiant exhaust heat will flow back there and be trapped up against the hood with really nowhere else to go. Though your filter may very well be full upon checking shortly after a good ride, have you tried putting your finger on the outside of that glass filter or looking at the fuel level in the filter ten minutes or so later?

Personally, and with your present routing in mind, I'd move that filter very close to the carb fuel inlet and place a small metal heat shield below it at the intake to guard against rising exhaust heat. The carb inlet position will be much cooler than where the filter is now, IMO.
 

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That is similar to what I did with my 2.2 EFI motor. I ran stainless braided lines both the supply and the return from the tank up the left side of the car until I got to the firewall and then went straight up next to the starter and then around the back of the valve cover. I don't think I have any pictures of the exact routing.
 

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'72 Opel GT (Sara)
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2,119 Posts
Discussion Starter #4
. . . nice job and generally well thought out . . . except that your fuel filter is located in what is perhaps the GT's hottest underhood spot!

Forced hot air drawn from the radiator and radiant exhaust heat will flow back there and be trapped up against the hood with really nowhere else to go. Though your filter may very well be full upon checking shortly after a good ride, have you tried putting your finger on the outside of that glass filter or looking at the fuel level in the filter ten minutes or so later?

Personally, and with your present routing in mind, I'd move that filter very close to the carb fuel inlet and place a small metal heat shield below it at the intake to guard against rising exhaust heat. The carb inlet position will be much cooler than where the filter is now, IMO.
I was basing the fuel filter location on minimizing its proximity to a heat source (assuming the hot air would whisk by out the back of the hood) and hadn't considered heat being trapped back there after a stop. Thanks for the tip!

Matt
 

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The glass filters also have o-ring seals. So something else to consider is if the o-rings get hardened and leak due to the heat or the glass cracks, guess where the fuel is going? Right on the exhaust manifold.

JM2Cs

Jc
 

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'72 Opel GT (Sara)
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2,119 Posts
Discussion Starter #6
The glass filters also have o-ring seals. So something else to consider is if the o-rings get hardened and leak due to the heat or the glass cracks, guess where the fuel is going? Right on the exhaust manifold.

JM2Cs

Jc
That certainly would be a problem! Personally, I change out the fuel filter every few months (probably way more frequently than I have to) just because. I also pop the hood every night after driving the car to let heat escape faster to spare the belts and hoses. Again, probably not necessary but it's a habit I've gotten into and only takes a couple seconds. So, in my case I have almost daily inspections under the hood and frequent fuel filter changes as preventative measures.
 

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Second thought, even better . . .

. . . nice job and generally well thought out . . . except that . . .

. . . I'd move that filter very close to the carb fuel inlet and place a small metal heat shield below it at the intake to guard against rising exhaust heat. The carb inlet position will be much cooler than where the filter is now, IMO.
. . . would be to move the filter to the driver-side of the engine (MUCH cooler, pic 2) and perhaps tie-wrap it to the accelerator linkage bracket outer hole to secure it. All you'd need is a two inch length (2") of original nylon fuel line and two hose clamps in addition to what you already have . . . nothing else!

Here's how:
1. Make single cut in existing fuel hose on driver-side 1" below accelerator linkage bracket and place new hose clamps over each end of hose just cut.
2. Loosen hose clamps on both sides of fuel filter and remove filter.
3. Insert 2" nylon fuel line halfway into carb-side hose of just removed filter and secure with existing hose clamp.
4. Butt both ends of filter hoses together over nylon line and secure with second existing hose clamp.
5. Back on driver-side, orient fuel filter, push hoses over filter nipples on each side and secure with new hose clamps.
6. Tie-wrap or otherwise secure filter in place, as necessary.

. . . simple, no?! :approve:
 

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Whoa hold on here...I thought the recommedations was to run it across the front bottom of the radiator to help stop the heat from generating a fuel vapor lock situation and then from the passenger side radiator support to carb ( I just have one fuel filter between tank and fuel pump mounted on drivers side low. I just ran the lines yesterday but have not installed the pump or set timing yet probable tonight after work and it's not too late to change the routing.
 

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'72 Opel GT (Sara)
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2,119 Posts
Discussion Starter #9
. . . would be to move the filter to the driver-side of the engine (MUCH cooler, pic 2) and perhaps tie-wrap it to the accelerator linkage bracket outer hole to secure it...
Thanks - that sounds like a better arrangement.

Whoa hold on here...I thought the recommendations was to run it across the front bottom of the radiator to help stop the heat from generating a fuel vapor lock situation and then from the passenger side radiator support to carb...
I'm sure there are other solutions that work equally well. This route just happens to be working well for me. The alternate location for the fuel filter suggested by tekenaar should further improve the set-up.

Matt
 
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