TBI Electronic Distributor Conversion with Instructional Video

For Throttle Body Injection operation, it is necessary to convert the point style distributor to an electronic unit.  This can be done via one of the two options that follow. In addition to the distributor conversion, you’ll need to upgrade your coil to one of the ones listed below.

Option 1 (Preferred Method) –  Lucas Conversion Kit from Patton Machine

These instructions cover an original Lucas distributor conversion to electronic operation with timing controlled by the ECM. This is the preferred method as it will provide complete ECM control and ignition mapping for you car.

Look over the following procedure and if you aren’t confident doing it yourself, I will gladly do the modification for you. If you would like me to do the conversion for you, send me your distributor and the cost will be an additional $50.00 plus return shipping costs.

For a fully functional TBI system your original Lucas distributor needs to be converted from a contact point type to electronic. The magnetic pick up assembly provides a steady timing signal to the ECM to monitor engine RPM. For use with the TBI conversion, both the vacuum and mechanical advance will be disabled. What we are about to do can be reversed should you ever decide to go back to original equipment, not that you ever would.

In addition to the instructions below there are two videos at the very bottom of this page.


With the engine at Top Dead Center, remove the distributor cap. Make note of the rotor’s position (should be pointing toward #1 plug wire); do not turn the engine until the distributor has been reinstalled. Working on a bench with a vise makes things much easier. If you have a mechanical tachometer remove the cable by loosening the knurled nut on the side of the distributor. The wires need to be labeled and disconnected. Remove the bolt from hold down clamp at the base of the distributor. Pull out the distributor with a twisting motion. Lightly clamp the bottom section of the distributor shaft in a vise.

To remove the breaker point plate you will need a small Phillips screwdriver for the two little screws on the plate. After removing the two little screws, swing the plate up and over the center post pivoting on the spring linkage of the vacuum advance. Reach in with a small flat blade screwdriver and slip the vacuum spring linkage off the post. You should now have the breaker plate in hand.

Grab the upper portion of the shaft with the cam lobes and see if it will rotate slightly on the shaft. This rotation is controlled by the weights down inside the housing. Now remove the screw in the center of the shaft with a flat blade screwdriver. Does the shaft lift slightly before the springs get tight? If not, the two shafts are probably rusted together. Free up these parts using a combination of penetrating oils and perhaps gentle heat, (be careful as the tach drive gear is plastic).

If the shafts are free to rotate, using a small flat blade screwdriver reach down inside and disconnect the two springs. Careful not to harm the springs if you may someday want to restore the distributor to original specs. With the springs disconnected the upper shaft will simply lift out. The weights are no longer used so set them aside.

The removed upper shaft will look like the photo.

Shown here is the new shaft and reluctor assembly. It is a precise fit onto the spring posts. NOTE: IT IS DIRECTIONAL AND WILL ONLY FIT WHEN ALIGNED PROPERLY! You may need to rotate the assembly 180 degrees for proper alignment.

It should be a sliding fit with the spring posts sticking up roughly 1/4″ above the plate. If the fit is too tight due to variances in the spring posts you may need to open the drive plate notches ever so slightly with a file. It’s not time to actually install the shaft assembly now so set it aside.

Shown here is the magnetic pick up mounted to a stainless plate. The red arrow highlights a screw used to adjust the air gap between the pick up and the ridges of the reluctor. To install this assembly first set the reluctor in place and engage it’s drive plate over the pins. Then lift it slightly to slip the pick up assembly in place. Carefully tighten the two screws that hold the plate to the housing while rotating the distributor shaft checking there is no interference between the reluctor and the pick up. With the shaft assembly back in place install and tighten the screw in the recess at the top of the shaft. You may need to loosen the adjustment screw to increase the clearance.

Looking good. The red arrow highlights the air gap between the reluctor and the pick up. It will vary a few thousandths as the distributor shaft is rotated. Best to have the distributor in hand when adjusting the air gap. You can use a feeler gauge, but there is easier and more accurate way to set the width of the gap. Maximum gap is 0.006″, set by loosening the adjustment screw and pivoting the pick up. Carefully tighten and recheck the air gap. I find it easier to use a strip of copy paper folded once instead of a feeler gauge. If you hold the distributor up to a bright light you can see the gap.The tighter the gap the stronger the signal. Too wide a gap, especially at low cranking rpm can cause hard starting. The same theory applies to rpm, the higher the RPM the stronger the signal. Don’t be afraid of tightening gap as close as possible without the reluctor hitting the pole piece of the P/U coil. Before reinstalling the distributor put the rotor on and snap the dist cap on. Hold the distributor to you ear and listen as you turn the dist shaft by hand and check that there is no binding or rubbing. Install your new electronic distributor!

The red connector from the pick up goes to the spade terminals on the module.. The ring terminal on the shield wire connects to one of the module mounting screws.

Coils suitable for use with the TBI conversion using the converted distributor and ignition module that is part of the kit. Most original coils will work as the ignition module is current limiting. The specs are as follows 40,000 Volts, Primary resistance 1.5 to 3.0 ohm, 12Volt, negative ground. You may use an externally ballasted coil with the ballast resistor or resistor wire bypassed.

See Pertronix note below

Pertronix 40001, 40011, or 40111

Crane PS20 or PS40

NOTE: It’s always a good idea to have a fire extinguisher handy when starting the car for the first few times. Turn on the key and you’ll hear the fuel pump run and then stop. Check for leaks at all fuel line connections.

Make sure the Ballast Resistor Wire has been bypassed.

Be sure the coil is getting full battery voltage when running. With the engine running measure from the + post of the coil to ground on the engine block. Do not use the (-) marked post on the coil as the ground for your meter. You should read 13.0V to 14V with the engine running unless the battery requires a charge. Compare the voltage reading with the reading across the battery terminals. Comparing the reading should show a value within a few tenths of a volt. Instruction for the bypass can be found online thru Google, in Dan Masters TR250 – TR6 Electrical Maintenance Handbook, or you can contact me directly. You will need to know the year of the TR6 for the proper procedure.

Setting the timing when running fuel injection:

IMPORTANT: DISABLE THE FUEL PUMP OR DISCONNECT THE INJECTORS WHEN SETTING THE TIMING FOR FUEL INJECTION OPERATION! We’re NOT trying to start the car yet. We just going to set the timing by cranking the engine.

If the engine has not yet run on the converted distributor a backfire is possible so disabling the fuel supply will allow timing to be set safely.  Disconnect the single wire connector near the ignition module. Using a timing light while cranking the motor with the starter rotate the distributor until the timing is set to 14 degrees. If you don’t have a remote starter switch, you’ll need a helper to turn the key while you set the timing.

At the end of the procedure disconnect the battery cable for 15 seconds to have the ECM reset the timing. Now, if you check timing at idle it will be near 22 BTDC” and steady.

To complete the distributor installation, lock down the distributor and reconnect the single wire connector. Make sure you enable the injectors or fuel pump that you previously disabled.  Providing the ECM is connected to it’s sensors and powered up, you are now running a programmable computer controlled electronic ignition system! With a timing light you can check timing at various RPM’s. For instance, just above idle speed, timing should jump out to about 22 degrees.

IMPORTANT: When driving if you hear pinging the timing is probably too far advanced, drop it back a couple of degrees. Excessive pinging can damage the engine. From this point on the timing should not require further adjustment and, unless someone is really looking, the conversion is really hard to spot.

Option 2 – installation of a Pertronix Ignitor Electronic Ignition

This aftermarket component is readily available and typically costs about $100. With this option you don’t have the advantage of electronic ignition mapping as performed by the Engine Control Module (ECM). For that capability you’ll need to install my conversion kit as detailed in Option 1 above.

Please follow their directions for setting the timing.

NOTE: If you are running a Pertronix ignition, please check with Pertronix for the proper coil noting that there are two models of Pertronix Ignitor. The original Ignitor as used with most British cars requires a coil or coil/ballast resistor combination of at least 1.5 ohms while the Ignitor II has current limiting abilities.

The following two videos walk you through the conversion process for making your Lucas distributor an electronic distributor.

Here’s Part 1 of 2

And……. Part 2 of 2