Step 1:

Strip engine, throw carbs at cat, full flow case, install gas tank fittings, clean throttle valve.

Fuel Tank:

The first step is pulling the gas tank. With an EFI you will have a lot more fuel flowing through the lines. It will be plumbed so that the pump is as low as possible and the flow will be sucked through the filter to the pump, through the injector lines, past the regulator and the excess fuel will be dumped back into the top of the fuel tank. That arrangement better protects the pump, equalizes the pressure to all 4 injectors, and helps cool the injectors down.

So basically you need to add a return fitting and you need to make sure the fuel fitting is large enough. Some tanks only have a 1/8" hole under the fitting. Drill it out if necessary.

I obtained a couple small chunks of aluminum and had a local shop heliarc them onto the old tank. It took 10 minutes, cost $20 and next time I will go elsewhere. Drill the holes and tap with 1/4 pipe tap. Later you will flow test the system to find out if you have enough capacity. Note: My existing fuel fitting was already large enough. I added the extra fitting for a fuel reserve line.

Fuel Reserve:

While I had things apart I needed a fuel shutoff valve. The regular old 1/4" brass valves have pretty small holes. I found this 1/4" 3 way valve that had larger ports. They have a teflon valve and can be bought at boat stores. I took a 1/4" NPT elbow with a 3/8 hose barb and tapped the inside for a 1/8" NPT. The 1/8" NPT pipe nipple then threads into the elbow. Then it gets screwed into the extra port on the bottom of the gas tank. The 1/8" nipple sounds small but it's inside diameter is larger than the ports on the valve so it will work.

Here's the complete setup. I don't like that looped line but it works. In short, one side of the valve goes to the bottom of the tank, the other side goes to the pipe nipple that sticks up 1.5" into the tank. If you can get your hands on a solenoid switch for trucks with dual tanks then that may be a better way.

Fuel Return:

This is the top of the tank. I used the fitting for a vent line for a while. It will get a 90 degree elbow and be used for the fuel return and I'll add another port for the vent.

The vent doesn't need a big hole. I took a 90 degree 1/4" elbow and tapped the inside for a 1/8" NPT. Then I took an 1/8" plug and drilled a 1/4" hole most of the way through. I finished the hole with a .040" drill bit. Yes it's a very small vent hole but that is still larger than necessary. The final step is screwing the plug into the elbow and grinding it so the assembly can fit in the tank.

The vent then gets a 1/4"NPT with a hose barb and several feet of fuel line that will wrap around the tank and end at an old fuel filter below the tank.

UPDATE: During a recent non-destructive test of the fuel tank vent it worked perfectly. The system appears to be "sealed" well enough to sit upside down for several minutes. Testing was terminated after 1 quart of engine oil leaked onto the ground.

INSERT top tank picture here!!

Full Flow Engine:

The motor was stripped and I drilled and tapped the engine for full flow lines. See this page for the full flow procedure: Full Flow

Throttle Valve:

The Tim Systems controller uses a throttle position sensor and RPMs to calculate airflow until the turbo boost starts. Because of that, it's important to size the throttle valve to the engine. If you have maximum air flow at part throttle then the throttle position sensor (TPS) cannot properly do it's job and you will have a hard time dialing the engine. The actual size that runs best will depend on the capabilities of the engine to flow air.

For a 1600cc to 1915cc engine, Tim recommends a 1 5/8 (41mm) to 1 3/4 (44mm) single plate throttle body. If you choose to experiment then do the math below and aim for a 60 meters per second air flow rate as a starting point.

Calculating Average Air Speed through throttle body:

Calculate area of throttle body:

50mm throttle body with 10mm shaft

(50mm/2)^2 x 3.14 = 1962 square mm
Less shaft area = 50mm x 10mm = 500mm
Total throttle bore area = 1462 square mm or 14.62 sq cm

Calculate average air flow through body:

400cc/cylinder x 6000 RPMs x 2 /60 seconds/minute = 80,000 cc/sec

800,000 cc/sec / 14.62 sq cm = 5456 cm/sec or 54.56 meters/sec

The Escort 50 mm throttle body I have should be adequate for a 1600cc engine to about 6400 RPMs and will have a flow rate of 64 meters per second on a 1915cc engine at 6000 RPMs.

Cleaning up the Throttle Body:

Here's the Ford Escort throttle body I'm using. Notice the step just above the throttle plate and the two holes in the bottom.

The holes are for the idle valve and on street cars they are used to make sure the engine idles under various temperature conditions and air conditioning loads. We don't need that on an off road buggy and it's one less thing to break. A 4 lug VW lug nut fits in the holes pretty well so that's what I used. Others have threaded them for a pipe plug. I then used a Standard Abrasives porting kit to smooth out the step and cleanup the inside of the throttle body. The leading edge of the throttle plate was rounded and the trailing edge was knife-edged for better flow efficiency. Cleaning up the throttle body wasn't necessary but what the heck, it didn't take long. BTW, that small hole you see just above the throttle plate is in a real good place for a vacuum advance/ pressure retard port for the distributor. (More on that later after I get my hands on the right distributor)

This is how the buggy sits now:

The next tasks will be making some parts for the intake manifold.

[ Step 1: Fuel Tank ] [ Step 2: Flanges and Plenum ] [ Step 3: Runners and Rails ] [ Step 4: Plumbing and Testing ] [ Step 5: Computer Wiring and Tuning ]