FUEL INJECTION CONVERSION, 1966 390

Tech Tips > 1964 - 1966 Tips > Fuel Injection Conversion, 1966 390

Fuel Injection Retrofit:

Recently we installed a Holley Pro-Jection fuel injection kit onto my 1966 Thunderbird town hardtop, 390 with Cruisomatic transmission. I am not particularly happy with the original Autolite carburetor or todays gasoline. I have been getting poor gas mileage and poor performance so I wanted to know if there were products out there that could be adapted to my car, keep it fairly stock yet help me solve these problems. I was also hoping that it would not be too expensive to install and set up and that my performance and economy would increase. 

The system turned out to be quite time consuming to install and the kit costs $935. All in all we had somewhere between 80-100 hours involved. Included in these hours was fixing a big rust hole in the trunk floor, installing a new exhaust system and installing new carpeting. What this should mean to you is that if you undertake such a project, plan on finding other problems along the way that will need attention while you have the car apart.

The fuel injection kit came with tuning and adjusting guide lines but no instructions for installation. Since the kit is generic and not specific to my car there are no installation instructions of any kind. This left us with creating our own installation design and procedure. The kit does mention not to install the computer in the engine compartment because of heat, oil and other such contamination.

The kit does not come with the fuel return line or any parts (adaptors) to connect the fuel return line to the car. The only thing the kit did include was the throttle body, manifold adaptors, computer and loom for the oxygen sensor. We had to purchase the oxygen sensor separately which was another $100 or so.

To make a long story short, we had to retro fit a new fuel supply line from the throttle body to the gas tank, electric fuel pump, fuel filters, trunk cover (shield) for fuel pump, locate and mount the computer, route all wiring, install the oxygen sensor into the exhaust system, etc.  Fuel injection requires a high fuel pressure which the stock mechanical fuel pump cannot supply. You have no choice but to install the supplied electric fuel pump. The fuel injection does not use all the supplied fuel and therefore must return the surplus back to the fuel tank thus the fuel return line. We used the original fuel line and sending unit as our return line and adapted a new fuel line for the supply.

So instead of writing a long boring article about our trials and tribulations, I will just post a bunch of photos I took and make a few notes on each photo.  We are still in the testing phase since we killed the transmission and it is still at the transmission shop. We need more time to test the gas mileage and performance. I will say that performance is considerably better but we are uncertain still about the fuel economy benefit. I will know more later on after more testing.

We took a new gas tank and drilled a hole and welded a fitting to attach the new fuel supply line. We used this line for our fuel supply line and the original fuel line and sending unit was used as the return. This fitting was welded to the rear drivers side bottom of the tank. It exited out the tank and into the trunk.

another image shows the location of the fitting.

We cut open the fuel line on the sending unit where it goes inside the tank so the return fuel can exit easily. We figured that the return line should be as near the top of the tank as possible so we used the original fuel line and sending unit because it is very near the top of the tank.

This image shows the location on the trunk wall where we cut a hole for the fuel tank fitting to stick through. We ran the fuel line into the trunk, mounted the fuel pump and filter into the trunk and went from there back to the throttle body.

Here you can see the hole for the fuel tank fitting, 6 mounting brackets for the shield to cover the fuel pump and filter, and two rubber mounts for the fuel pump.

Here are two of the floor brackets for the fuel pump shield.

Here is one wall mounted bracket for the fuel pump shield. You can see we used nut plates for the retaining screws.

This is the shield cover for the fuel pump and filters to protect them and to finish off the trunk floor nicely.

This is how the trunk floor looked after we insulated it but before the mat kit went in.

Here are the rubber mounts for the fuel pump itself (center).

Here we mounted the fuel pump to a '65-'66 sequential turn signal bag rubber mount. We cut the original mounting extentions off. So, we have the motor rubber mounted to the sequential mount and we have the sequential mount rubber mounted to the trunk floor. When the car is running you can not hear the fuel pump running inside or outside of the car.

Here is what the fuel pump and filters looked like after they were installed. There are two filters, the white one and the silver one. Here the fuel pump has a black insulationg cover and is in the middle. You can see the fuel line exits out the passenger side of the trunk. You can also see the electrical wires to the fuel pump. We ran these wires through the center console, under the back seat, into the trunk and to the electric fuel pump. The instructions do suggest mounting the electric fuel pump under the car but we thought this would look unprofessional. Besides, there is far too much contamination under the car. Nothing well ever happen to the fuel pump and its related parts in the trunk. We wanted to keep the factory original look under the car as well.

We cut a hole in the right wall of the trunk, bought a special fitting that bolts to the wall and attached our fuel lines to that. The fuel line actually passes through the fitting, it isnt part of the fitting. This keeps the fuel line secure and keeps it from chaffing against a sharp edge of the trunk wall.

You can see the fuel line is rigidly attached to the trunk wall. It then goes up to the bottom of the body above the gas tank and across to meet the original fuel line. We sealed all holes through the trunk walls with fast urethane.

looking up from under the car on the drivers side to the passenger side, you see the new fuel line coming across the top to meet the original fuel line. In the foreground is the diff. The gas tank is behind the diff. The rubber hose that fits onto the original fuel line to the sending unit is off at the moment.

Here you can see the two fuel lines side by side as they pass in front of the drivers side leaf spring pirch.

Here you see both fuel lines side by side going up to the front of the car along the drivers rocker. Anyone looking under the car would be hard pressed to see anything out of place. Only a keen eye would notice two fuel lines.

Here you see both fuel lines routed up through the drivers inner fender well and up along the firewall. You can just make out the steering coupler and steering column mounting bracket. We had to remove the original fuel line here, take a new identical fuel line and rebend both to fit the firewall since the throttle body has both the fuel inlet and outlet coming out the back instead of the front like the original carburetor.

These are the two fuel lines to the fuel injection throttle body that we had to rebend and fit onto the firewall. They are already bent and ready for installation as seen in the previous photo above.

Here you see the two fuel lines installed in the car and hooked up to the throttle body. You can see the firewall, throttle linkage on the back of the intake manifold and brake booster hose in the middle.

From this drivers side view of the fuel injection throttle body you can see both fuel lines hooked up, all the throttle linkage hooked up, the electric idle compensator which serves both as a dash pot and fast idle solenoid for the choke. We used a throttle rod from a cruise car which hooks up to the carb via a stud. The throttle rod has a flat end with a hole for the stud which is bolted to the throttle arm on the carb. The fuel injection throttle body lever didn't have the correct configuration to use a non-cruise style throttle rod which has a 90 degree bent end and a retaining clip. The throttle body looks similar to a 2 barrel carb but it has ultimately more CFM's then the original Autolite carb.

Here are the fuel injection looms to the computer routed from the throttle body down behind the engine into the transmission tunnel and up through the oval access hole on the top of the tunnel as seen in the next photo. In this photo the fuel lines pictured above have not yet been installed.

We made two holes in the oval access hole plastic plug and passed the looms through the holes then sealed them with fast urethane, a black silicone type substance that is used to seal windshields. You can see two looms routed back and one routed to the passenger side. That is the power feed to the fuse box. You can see that we ran that under the carpet at the top of the floor pan where the vacuum hose for the emergency brake goes.

Here you see how we mounted the computer directly the passenger seat. See the loom come through  a hole in the carpet. We used a dimmer switch grommet to fill the hole in the carpet which gives the loom something smooth to pass through. The instructions say not to install the computer in the engine compartment because of heat, dirt and oil will damage the unit. By installing it under the passenger seat, we were able to adjust the computer while driving the car. If it were under the hood you could not make adjustment while driving which are critical and necessary.

Here you see how we hooked up the fuel injection computer electrical to a relay connected to the fuel box.

This is the optional oxygen sensor we had to buy seperately. The kit comes with the wires to the sensor but not the sensor. We installed it onto the passenger side header pipe as close to the engine as possible. The sensor points down towards the ground so we can have full access to it.

This is the mounting boss for the oxygen sensor that we welded into the header pipe.

Finish product. Engine compartment looks stock. Original air cleaner fits perfectly. There are almost no immediate sign that anything has been done.

Drivers side view. Everything looks stock.

Passenger side view. Everything looks stock.

Here I am taking credit for all the installation work. Actually I commissioned my ace technician Clark Gillie to do this job from start to finish. He did a very professional, quality job.

Clark hard at work making the fuel pump shield for the trunk.