Part 2 – Fuel System
An EFI conversion on a classic car requires a regulated, high-pressure fuel source. Which means a whole new fuel system. Because I chose to use a Throttle Body Injection (TBI) system I’ll need a fuel pressure of approx 15-20 PSI. If I had chosen port injection, then I would have had to use higher pressure fuel injectors and run the fuel pressure at 35-40PSI. Because of the lower pressure of the TBI system there are a few more options available for fuel lines and connectors.

Fuel Tank:
Factory EFI vehicles have baffles in the fuel tanks to make sure that on hard cornering the fuel pump doesn’t end up sucking air into the fuel system. This is usually more of a problem when the fuel level is low. In a carbed vehicle, this isn’t a problem as it’ll “burp” through the carburetor. I’ve chosen not to install a baffle at this point. Mostly because I’ve been told that this really isn’t a problem until you get below ¼ tank. Since this is a weekend car, I don’t see that being a big concern. For now I’m going to try it without and see what happens. If it turns out to be a problem I’ll investigate installing baffles, or perhaps a surge tank.

Fuel Return and Pickup:

Because a regulated fuel pressure system needs a return line, you must run a return line from the fuel pressure regulator back to the tank. In most cases this means a 2nd fuel line all the way from the engine to the fuel tank.

There are a few different options for attaching a return line to your fuel tank. The easiest would probably be to use the drain plug. Unfortunately my fuel tank was not fitted with a drain plug. The other easy option is to tap into the fuel tank’s rubber filler neck. However, for the cleanest look without too much effort, I decided to modify my fuel level sender.

As you can see in thes picture, I drilled a hole in the fuel level sender’s plate and then had a fitting brazed on by a local shop. Apparently I made a poor choice in fitting materials as brass and steel are apparently very hard to braze… hence the “booger” welding by the shop. A steel connector would have been much easier to weld and the welds probably would have looked a lot cleaner. However…it’s effective and doesn’t leak, so that’s all that matters in this case.

The fitting I used was a 3/8th’s NPT to 3/8ths hose barb. The red line shows where I cut the threaded portion of the fitting off to leave only the barbed portion. Again, apparently steel is a better choice than brass for ease of welding.

Here’s a picture of the fuel sender mounted back on the tank along with the lines and pre-filter. At this point, neither of the fuel lines will see high pressure and you can use regular low pressure hose. The supply line is low pressure because this is all before the pump, and the return line feeds directly to the tank so it’s also low pressure. For best performance you want to mount the pre-pump filter and fuel lines as low as possible. The location I used should be fine, but mounting a few inches lower would be ideal.

Fuel Line:
Routing the fuel line was straightforward. I mostly followed the same path as the stock line. Here is a picture of the fuel line and fittings I used. See part 1 for more information on this line. See Part 1 for more info on this hose or the fittings.

Fuel Pump: I chose this location to mount the fuel pump mostly because it was low (the lower the better) and I already had holes and mounting hardware in the frame rails from a removed anti-sway bar (victim of lowering). From the pump to the fuel pressure regulator you will have to use a fuel line capable of handling the higher fuel pressure.

Fuel Pressure Regulator and Injectors
Using throttle body injection is nice because you cram a bunch of different EFI components into a single package. The Holley TBI I purchased has the throttle plate, the Throttle Position Sensor, the fuel pressure regulator, fuel rails, fuel injectors, and idle air control all built into a single unit. Installing the TBI unit is much the same as installing a carburetor.

In this picture you can see the fuel lines enter the throttle body. The high pressure filter is hidden under the export brace. You’ll also notice the fuel pressure gage that I mounted directly to the throttle body using a plugged port that was created during the throttle body machining process. The air cleaner wraps around the gage perfectly, but you must remove the air cleaner base to read the gage.