Wednesday, January 25, 2017

Fuel System Install Part 1 – Rear Soft Lines and In-Tank Fuel Pump

A little while ago, it was decided that the Boss would get fuel injection.  However, the intent in the whole plan was to make the injection system as “minimalistic” in appearance as possible.  In other words, when the hood is raised, the intent is that the engine bay carries “the look” of a modified engine bay belonging to a Boss 302.

Until rather recently, there were no throttle body injection systems that quite fit the bill.  But now, the market has almost exploded with very reasonably priced and well-rounded systems that satisfy “the look” as well as the functionality and convenience of modern fuel injection.

Since our path is determined, the time had come to start configuring the fuel system to support a sporty fuel injected engine combination, while maintaining “the look” as much as possible all over the car.  I admit, I’ve always wanted people to have to really work to take in all of the details of this build (and there are/will be THOUSANDS), with some being relatively obvious and clearly drawing attention while many others lurk in your subconscious before your eye recognizes them.

For a long time, I have been a fan of Aeromotive fuel system components, so it was a natural fit that we would choose their Phantom 340 Stealth in-tank fuel pump system as our go-to combination.  This kit is of exceptional quality and installation is relatively straight forward.  However, the entire system would require quite a lot of plumbing and careful component selection to ensure peak performance and longevity in a clean and unassuming package.  So, that’s where we started.

First on the agenda was to select proper fuel line materials and fittings along with a routing path that worked well the full length of the floor to the engine bay.  For fuel line, the first reaction by many is to install the venerable braided stainless lines with AN fittings.  While the AN fittings are more than adequate, the typical braided stainless fuel line isn’t really optimum for modern injection systems and fuels. 

The biggest problem with typical rubber AN lines is they essentially out gas fuel vapor over their lifetime at a fairly high rate (about 1 gallon fuel loss per foot of -06 hose per year!).  The two solutions are a Teflon lined AN hose or a modern rubber fuel injection hose like Gates Barricade.  With the Gates product, fuel vapor loss is eliminated and the flexibility and ease use makes it a perfect candidate for a modern hot rod when trying to keep the appearance subtle.  And best of all, the availability of push-on AN fittings like the Aeroquip AQP Socketless fittings makes this system capable of satisfying all of our needs in a simple package.

Another consideration is that running flexible AN lines for the length of the car makes for a difficult routing job and makes cleanliness an even tougher objective.  In our case, the soft lines are exclusive to the front and rear zones of the car with the connection between them (and the longest runs) taken up by the use of “Cunifer” metal hard lines.  Cunifer lines are among the very finest available and are an alloy of copper (Cu), nickel (Ni) and iron (Fe) in a 60/20/20% typical composition respectively.  They are highly resistant to corrosion, bend and flare beautifully, and are most often found in brake lines on higher-end performance and racing cars all over the world.

Our fuel system would be a combination of soft and hard lines beginning in the trunk and ending in the engine bay.  The first order of business was to carefully plan the entire feed and return circuit route from front to back and measure and sketch the plan making notes on component placement, bend locations, fittings required and component clearance.  At the same time, we needed to make sure the entire system was easily accessible and serviceable anywhere the car would be driven.
With our line plan established, we set off to plumbing the soft lines at the rear of the car.  This began with installation of the bulkhead fittings exiting the trunk area on the right side of the car as well as installing the mating fittings at the front of the car in the engine bay.  This established our absolute “pierce points” at the front and back and we could now easily visualize the start and end of our under-car fuel system.

Next, we mounted the Aeromotive 10-micron fuel filter and bracket in its predetermined spot, inboard of the rear sub frame.  The filter is, of course, another pair of absolute hard points and needed to be permanently positions to allow accurate routing of the soft lines in and out.

With the hard points now finalized, we began fabricating the rear soft lines starting at the rear and working forward to the filter.  I like to install an AN fitting in the free end of the hose and mount it to the bulkhead fitting so it is a stable and easy reference while routing the rest of the line in the most optimum way.  This acts as a “third hand” in a way and makes routing so much easier.

Once the feed line route to the filter is finalized, I cut the line about a foot longer than required and move to the return line.  The return line is routed it along the same path, and the line is cut at the same length as the feed line to ensure we can match the fitting locations as they join the chassis hard lines that we will make later on.

To aid in securing the lines and maintaining the proper routing, we used a few aluminum line clamps that secure and separate the feed and return soft lines and allow them to be mounted to the chassis in a very clean way.

With the rear soft lines in place, it was time to address the installation of the Aeromotive in-tank fuel pump system.  This kit is a rather amazing piece of business that allows almost any original muscle car fuel tank to be converted to a modern, in-tank electric fuel pump module in an evening.  The process, in fact, is pretty straight forward, with the most critical and complicated event being that of properly positioning and cutting the hole in the top of the tank for the pump mount.  Once the hole is cut to the proper 3.25” diameter, a nifty positioning ring is used to establish the drill pattern for the 10 mounting studs to pass through the top of the tank from the inside stud flange out.

Deburring the fresh holes is going to be a challenge, especially if you have ham fists like mine and can barely get a paw down the hole to try to access the drilled holes from inside.  A skinny, malnourished, but enthusiastic helper will go a long way in this endeavor for little more investment that a few pops and a box of Band-Aids.

Next, it is best to vacuum out as much of the chips and debris from the tank as possible followed by a thorough washing with a solution of simple green and water.  This will do a very good job of getting all of the metallic dust and schmutz out of the tank so no future damage to the pump will occur.  Of course, the tank should be dried completely before installing the pump module components.

With the tank modifications complete and the inside washed and dried, the foam and ballistic rubber “basket” can be trimmed to fit the tank depth (plus 1 inch).  Once that is complete, and with the help of the pattern fixture, the basket can be inserted into the tank.  The compression on the foam will act to help retain the stud ring and make the rest of the installation much easier.  With that, the hardest part of the installation is over!

At this point, the pump hanger is measured and trimmed to make the pump module overall length a match to the tank depth and the module is assembled as a unit for the final time.  Next, the pump flange gasket is placed over the mounting studs and the pump module is lowered into the foam basket and secured to the studs with the sealing washers and lock nuts provided in the kit.

While this is a bit of an oversimplified account, the project is certainly worth the effort and all of the included hardware is of the finest quality.  The remaining electrical connectors and wiring terminal boots will be saved for the wiring project later on, but for now, the tank is complete and we will move on to mounting it in the chassis and finishing the soft lines in the trunk area.

From here, we will move on to fabricating the front soft lines and finish it up by fabricating the hard lines to connect the works together.  Look for Part 2 soon!

We start by laying out the position of each AN bulkhead fitting so the fuel line "end-points" can be established. 
With the hole positions established, the centers are marked and pilot drilled.

A Uni-Bit is the best tool to open up nice clean holes in sheet metal.  Here, the second bulkhead fitting hole is drilled in the right side trunk area.
With the bulkhead fittings in place, the trunk fittings look especially clean.  The silver-white washers are actually Earl's Stat-O-Seal washers that provide a weather tight seal to the fittings.

On the opposite side of the trunk floor, the feed and return line end point fittings are put into place to ensure proper fit.
The front engine bay apron bulkhead fittings are next and install in exactly the same way as the trunk fittings.

From inside the engine bay, the feed and return fittings are very unassuming and tidy.

The final "hard point" element is the 10-micron fuel filter and bracket.  Here we have mounted the assembly in a secure location just inside of the right rear sub frame.

Using Gates Barricade fuel injection hose, we plumb the soft lines at the rear of the car by anchoring the rear trunk fittings first.  This acts as a "third hand" when routing the fuel lines by maintaining a firm anchor to the ends of each line, allowing full freedom to route the lines in the best possible way without a bundle of snakes coiling up behind you as you go.

Here are the soft lines for the feed and return circuits completed.  Notice there are a minimal number of fittings and no severe bends of disruptions in the line routing.  Smooth is good!

Here is an awesome little tip.  This is an Oetiker clamp (often called an ear clamp).  I use these extensively on high pressure fluid lines as they do not damage the rubber jacket of the line and they clamp very snugly around the entire circumference of the line.  These make worm-screw clamps look like something less than civilized.

Here are the aluminum line separator clamps I use when routing fluid hoses.  Th bolt in the center is modified to no only close the clamp but to mount it to the chassis as well.

Fuel pump installation begins by carefully positioning and then drilling the 3 1/4" hole in the top of the tank that allows the pump module to pass through. 

With the hole cut, the painful deburring process can begin.  The large hole is by far the easiest to deburr.  The whole game changes when the smaller mounting stud holes are drilled.......
This clever pattern fixture is included in the kit and helps to position the flange mounting holes as well as aid in the installation of the pump basket later on.
With the mounting hole pattern carefully mapped, the fixture is used to drill the 10 mounting holes required.  Once that is done, its best to kidnap a skinny car enthusiast that need money to reach in and deburr the holes for you.  Trust me, it's worth the investment in Band-Aids, smokes, beers, booty or whatever, 'cuz you WILL get cut otherwise.  Get it?

Once ll of the drilling and deburring work is complete,. the tank is thoroughly vacuumed out and then washed with Simple Green and water to get all of the remaining crap out.
With the tank depth accurately measured, the filter basket foam is marked and cut to size.  The foam is always cut 1 inch LONGER than the measured tank depth to ensure proper fit.
The interior stud ring ins placed inside the tank and held in place by the pattern fixture.  Notice the smooth funnel shape the fixture has?  This will make installing the foam basket a piece of cake shortly.
And just like that, the foam basket in inserted into the tank and the compression against the bottom of the mounting stud ring inside is enough to keep it in place during the rest of the install.

Here's a little detail that is not mentioned in the instructions:  This little dust cap must be removed from the pump inlet and outlet before the pump can be installed.  very easy to overlook if you don't know what to look for.
With the pump hanger bracket measured and trimmed to fit, the pump assembly is mounted to match the tank depth and the entire assembly is lowered into the tank over the thick foam sealing gasket and mounting studs.

The nuts and sealing washers are snugged up around the mounting flange and the installation is done!  The finished product looks mighty impressive and will support our fuel injection system with ease.
Here's a clever shot of the fuel pump module and foam basket mounted in the tank.  You can see the basket is flush with the bottom of the tank floor and doesn't interfere with any feature inside the tank.  With the exception of the small tuft of paper towel fluff I deposited into the tank just prior to this picture, the tank is clean and ready for battle.  Thank God for Shop-Vacs!


  1. Wow - that looks great Sven! Love the tip for the gas line clamps - I hate those worm gear types!!

    So one question - how does the top of the fuel pump flange account for the ridges in the fuel tank panel? It looks like it will pull down tight against the high part of the channels but is there a length of exposed fastener in the 'valleys'. Seems like there needs to be some sort of adapter to account for the uneven nature of the top of the tank. If that makes sense the way I've phrased it?


    1. Thanks RJ! The Key to effective use of the Oetiker clamps is investing in a really good clamp tool.

      As for the fuel pump top flange seal, there is a 1/2" thick, dense foam gasket that conforms to the tank ribbing and seals the works very well. It's a pretty commonly used material in fuel system to seel oddball shapes like this.

  2. Wow, that must be some fairly trick material to maintain a seal with the large gaps present in the tank ribbing. Who would have guessed! I've been using 3D printing technology in our robotic builds over the past couple years. As the materials you can print with have evolved, there are all sorts of cool uses for it now. It used to be only for non-working prototypes, but the materials have improved to the point we use it for actual parts now. I was thinking it would be fairly easy to design and print a flange adapter that would require not much more than some sealant to get a nice tight seal. I'm quite sure SusieQ has some 3D printing technology headed her way :) Looking forward to your 2017 build - looks like some good progress coming from you!!! Hang in there - we are pulling for you! rj

    1. The gasket itself is a tick over 1/2" thick and I think it's expanded neoprene foam (not sure).

      I LOVE the evolution of 3D printing and can easily foresee adding that technology to my future builds and shop capabilities but I have a lot to learn! We have some AMAZING 3D technologies at my "day job" and it makes my head run overtime thinking about what the possibilities could be. Gotta get trained up on a reasonably affordably 3D design program first I reckon!

  3. As usual, your engineering and workmanship are stellar Sven. Just out of curiosity, are the fuel lines running down the passenger side instead of the driver's side? Sometime tells me your progress on Night Mission will accelerate as fast as she will be when you're done!

    1. Thank you Dennis! And yes, the fuel feed and return lines run inside the right side frame rail and subframe connector. They have been routed so as not to be visible from outside with the car at ride height.

  4. BEAUTIFUL CAR !! can you tell me how your fuel line is holding up, and what size clamps you used ? I am in the fuel line install part of the swap and have heard good things about the gates barricade fuel injection hose.

    thanks, Mike

    1. Hello Mike and thank you!

      While this car has yet to run, I use Gates Barricade hose in several other applications with excellent results. I find it much more user friendly and allows a lot less vapor permeation than most braided lines and is easy to work with and has a certain "factory" look to it as well.

      The clamps I use are Oeticker stainless clamps in a 14.5-17.0mm range for the Gates 3/8" I.D. hose.