Building a (Semi) Hidden High Flow Fuel Delivery System Part 3

Wayne Scraba

27 Feb 2020

Click Here to Begin Slideshow When we last left you, the Holley HydraMat (introduced in the first issue of this series) was installed in the modified gas tank. If you recall, it was locked in place by means of a Holley magnet kit. In addition, if you spin your browser back, you’ll find the tank was set up with a number 10 bulkhead fitting for the pressure line, a number 8 bulkhead fitting for the fuel return line and a number 8 bulkhead fitting for the vent. The HydraMat we used came equipped with a large ½-inch NPT fitting (most are smaller). Sounds easy enough, but there were some hurdles: The dilemma here is that we needed to run two fuel lines inside the tank. We must use fuel safe hose for both of them. Fair enough, but where things get complicated is the fact that there aren’t many hoses out there that are actually “submersible” (meaning of course, they can be submersed in gasoline and survive in that not-so-pleasant environment). Adding to the predicament, there aren’t a lot of options when hose size increases to 5/8-inch in diameter (to match the #10 bulkhead at the front of the tank and the ½-inch NPT fitting on the HydraMat). After weeks of searching, a solution turned up: Tygon tubing. It is compatible with most fuels, including those that contain alcohol. It resists swelling and hardening (remains somewhat pliable) and maintains an air-tight seal under all sorts of temperature extremes. It is stiff enough that it will resist collapsing but it may eventually need servicing (replacement). Because of all of this, we figured it was the best compromise. By the way, you’ve probably seen this semi-clear yellowish fuel line fitted to numerous small engines. But where do you find Tygon hose with a 5/8-inch inside diameter? The ½-inch hose to match a number 8 fitting wasn’t too difficult to locate, but not so with the bigger stuff. We eventually discovered McMaster-Carr stocked it. It’s not bargain-basement priced, but then again, not much tubing is required. In order to go from the bulkhead fitting to the big pressure line, we used an Earl’s AT700111ERL fitting. On the HydraMat, we simply added an Earl’s ½-pipe to -10 AN adapter (part number SS981610ERL) and topped it off with an Earl’s AT709111ERL 90-degree fitting. This fitting, along with the others inside the tank, have an AN threaded swivel along with a barb on the other end. The barb is designed to be pushed into the hose. Holley does not recommend you use sealant of any sort on the HydraMat pipe threads. As a result, we snugged up the pipe thread adapter fitting and called it a day. The section of 5/8-inch Tygon tubing was cut to length and then affixed to the AN fitting nipples with double hose clamps per side. As a note here, be careful when sourcing hose clamps. There is a huge amount of (really awful) junk out there. We highly recommend Breeze hose clamps. They are used in the aircraft industry and are made in the USA. Our examples shown in the accompanying photos have a stainless band along with a plated hex screw. If you can’t find Breeze clamps locally, McMaster-Carr has them in stock. For the return line, the process was similar – an Earls #8 fitting (part number AT700109ERL) topside that went directly into a section of ½-inch Tygon tubing held in check with a pair of Breeze hose clamps. Obviously, the return line doesn’t attach to anything else inside the tank, but we did aim away from the pickup location. The vent inside the tank was very simple too. Here we simply used a 45-degree -8 hose end (with just the nipple in use) and angled it upward to the top of the tank. Once all of the clamps and fitting were tightened and double checked, the top inspection plate was installed. The only remaining piece of the puzzle was the gas cap. You have to be sure the cap you use for a tank such as this is non-vented and fits very tightly. Stant offers several examples that work. You might have to try a couple of different examples before you track one down that fits tightly on your tank filler neck. In the next issue, we’ll dig into the plumbing. Meanwhile, check out the accompanying slideshow. You’ll see how it all came together:

Building a (Semi) Hidden High Flow Fuel Delivery System Part 3 — Click Here to Begin Slideshow When we last left you, the Holley HydraMat (introduced in the first issue of this series) was installed in the modified gas tank. If you recall, it was locked in place by means of a Holley magnet kit. In addition, if you spin your browser back, you’ll find the tank was set up with a number 10 bulkhead fitting for the pressure line, a number 8 bulkhead fitting for the fuel return line and a number 8 bulkhead fitting for the vent. The HydraMat we used came equipped with a large ½-inch NPT fitting (most are smaller). Sounds easy enough, but there were some hurdles: The dilemma here is that we needed to run two fuel lines inside the tank. We must use fuel safe hose for both of them. Fair enough, but where things get complicated is the fact that there aren’t many hoses out there that are actually “submersible” (meaning of course, they can be submersed in gasoline and survive in that not-so-pleasant environment). Adding to the predicament, there aren’t a lot of options when hose size increases to 5/8-inch in diameter (to match the #10 bulkhead at the front of the tank and the ½-inch NPT fitting on the HydraMat). After weeks of searching, a solution turned up: Tygon tubing. It is compatible with most fuels, including those that contain alcohol. It resists swelling and hardening (remains somewhat pliable) and maintains an air-tight seal under all sorts of temperature extremes. It is stiff enough that it will resist collapsing but it may eventually need servicing (replacement). Because of all of this, we figured it was the best compromise. By the way, you’ve probably seen this semi-clear yellowish fuel line fitted to numerous small engines. But where do you find Tygon hose with a 5/8-inch inside diameter? The ½-inch hose to match a number 8 fitting wasn’t too difficult to locate, but not so with the bigger stuff. We eventually discovered McMaster-Carr stocked it. It’s not bargain-basement priced, but then again, not much tubing is required. In order to go from the bulkhead fitting to the big pressure line, we used an Earl’s AT700111ERL fitting. On the HydraMat, we simply added an Earl’s ½-pipe to -10 AN adapter (part number SS981610ERL) and topped it off with an Earl’s AT709111ERL 90-degree fitting. This fitting, along with the others inside the tank, have an AN threaded swivel along with a barb on the other end. The barb is designed to be pushed into the hose. Holley does not recommend you use sealant of any sort on the HydraMat pipe threads. As a result, we snugged up the pipe thread adapter fitting and called it a day. The section of 5/8-inch Tygon tubing was cut to length and then affixed to the AN fitting nipples with double hose clamps per side. As a note here, be careful when sourcing hose clamps. There is a huge amount of (really awful) junk out there. We highly recommend Breeze hose clamps. They are used in the aircraft industry and are made in the USA. Our examples shown in the accompanying photos have a stainless band along with a plated hex screw. If you can’t find Breeze clamps locally, McMaster-Carr has them in stock. For the return line, the process was similar – an Earls #8 fitting (part number AT700109ERL) topside that went directly into a section of ½-inch Tygon tubing held in check with a pair of Breeze hose clamps. Obviously, the return line doesn’t attach to anything else inside the tank, but we did aim away from the pickup location. The vent inside the tank was very simple too. Here we simply used a 45-degree -8 hose end (with just the nipple in use) and angled it upward to the top of the tank. Once all of the clamps and fitting were tightened and double checked, the top inspection plate was installed. The only remaining piece of the puzzle was the gas cap. You have to be sure the cap you use for a tank such as this is non-vented and fits very tightly. Stant offers several examples that work. You might have to try a couple of different examples before you track one down that fits tightly on your tank filler neck. In the next issue, we’ll dig into the plumbing. Meanwhile, check out the accompanying slideshow. You’ll see how it all came together:

In order to position the HydraMat, we temporarily installed the modified OEM fuel sender. This allowed us to position the HydraMat.

Here’s a look inside the tank. You can see the fuel level float in the center with the HydraMat offset to the right.

The Tygon hose was partially assembled and then marked for length. A set of hose cutters makes short work of the hose cut.

These are the Breeze hose clamps mentioned in the text. Quality is superb. And yes, you pay a bit more, but you sure do get what you paid for.

This is the completed fuel pickup line. It consists of Earl’s fittings with combination AN and barbed ends, the Tygon hose mentioned in the text and double Breeze hose clamps per side.

Once the fittings inside the tank were tightened, the access plate was screwed into place, as shown here.

We also installed the fuel sending unit at this time. Note that the fuel port is blocked off. Although you can’t see it, the inside is also capped.

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