Ignition BT7

Editor Update: Originally posted in 2012

The Original Ignition System

Distributor: Lucas DM6A

Coil: Lucas HA 12 volt

Spark Plugs: Champion UN12Y

Modified Ignition System

Distributor

Having converted the Bugeye to electronic ignition with a Crane system, I knew that I wanted to use electronic ignition with the Bloody Beast, but unlike the Crane system, I wanted to use a system that would be housed in the distributor such as a Pertronix. After doing some research I decided to replace the entire distributor with a newly introduced Dutch product, the 123 Distributor. The United States distributer is https://123ignitionusa.com

More information about the installation is provided in this website post: https://valvechatter.com/?p=12431

One appealing aspect of the 123 is that the advance curve is determined by simply adjusting the settings by turning an adjustment on the outside of the distributor and “clicking” it into place. Sixteen curves are available from which to select. Since my purchase the vendor has introduced a programmable bluetooth distributor that can be managed with a laptop. The model number of the unit I used is 123/GB-6-R-V.

For initial set-up, I chose the recommended “B” setting. While the distributor is a “drop-in” in for the BJ8 with an electronic tach, a kit is supplied to adapt it for the mechanical tach drive of the BT7. The shaft did need to be drilled and the drive dog from the original Lucas unit installed with a few spacing washers. My unit was supplied by a German vendor Brits’N’Pieces.

123 Distributor

123 Distributor

Lucas DM6A [Added to this post on August 17, 2020]

At some point I may go back to using the original distributor, so I decided to have it rebuilt by Jeff Schlemmer at Advanced Distributor . Jeff does a great job and he sets up the distributor for the owner’s particular situation. For example, although my car is 1960 BT7, I let him know that I am using a BJ8 cam, 2″ HD8 SU carbs, a Dennis Welch fast road aluminum head and etc. Instead of being set up for 5 degrees BTDC the distributor is set up for 15 degrees BTDC.

This is the exploded view of the unit as provided in the Service Manual

Lucas DM6A Distributor Drawing

Two great videos to watch about the Lucas distributor:

 

“Automatic timing control of the distributor is controlled by a centrifugal mechanism and a vacuum operated unit each operating entirely independently of each other. The centrifugal mechanism regulates the ignition advance according to engine speed, while the vacuum control varies the timing according to engine load. The combined effect of the two mechanisms gives added efficiency over the full operating range of the engine. A micrometer adjuster is provided to give a fine timing adjustment to allow for the engine condition in the grade of fuel used.” 

A keyed molded rotor with a metal electrode is mounted on top of the cam. Attached to the distributor body above the centrifugal advance mechanism is a contact breaker plate carrying the contact breaker points and a capacitor connected in parallel. A cover is fit over the distributor body and retained by two spring clips attached to the body.”

Breaker Plate Assembly:

DM6A Breaker Plate and Points

The Contact locking screws need to have both flat washers and shake proof (lock) washers under them. Care needs to be taken with the low tension wire lead. It is fragile and flexible and it needs to be because it moves when the vacuum advance shifts the breaker plate.

Adjusting the Points gap:

The Driver’s Handbook for the MKI and II 3000s states that the points gap should be checked every 6,000 miles. The gap of the contact breaker points should be set within .014” to .016.” The gap adjustment is made by rotating the engine until the heel of the fiber rocker is on the peak of one of the cam lobes. 

The contact locking screws should be loosened and the plate adjusted until the gap gauge is a sliding fit between the two contacts. Tighten the locking screws and recheck the gap. Replace the rotor and cover. Replace the points if they are dirty or pitted. The points can be cleaned with fine emery-cloth. This is easier to do if the breaker point carrier assembly is removed.

Lubricating the Distributor:

Oil is applied to/around the center screw under the rotor. It wicks down and allows the top half of the spindle to move relative to the bottom half (allowing the centrifugal advance to take place). 

To lube the bob weights and springs is a bit more involved, but these don’t have to be addressed very often – every couple of years. A good Moly grease would work fine.

Remove the distributor cap and rotor,

Disconnect the breaker plate to distributor housing ground wire if fitted,

Remove the screws securing the breaker plate to the distributor housing,

Remove the breaker plate.

With the breaker plate out of the way you will be able to see and lubricate the bob weights and springs. If you take the breaker plate apart it is a good idea to put Moly grease on the contact points between the two plates.

Apply a few drops of engine oil (or 3&1) at the pivot and contact locations.

When done, check your points gap and timing. Also apply a thin film of light grease to the distributor points opening cam Failure to lube the points cam can lead to very rapid wear of the heel block on the moving arm of the points.

Rotors and Condensers:

There have been a considerable number of poor quality rotors and condensers on the market. I just had my distributor rebuilt by Jeff Schlemmer at Advance Distributors and he installed a new red rotor that he claims will last 50,000 miles. I am told that the best condensers and rotors are sold by the Distributor Doctor http://www.distributordoctor.com. These condensers have soldered joints and yellow wires.

DM6A Rotor

Breaker Points:

These are available from a number of sources. The image below is the set available from the Distributor Doctor.

DM6A Points/Contact Breakers

When installing the points assembly it is important that the ground wires do not contact the mounting post. The following image and sketch done by Paul, on the British Car Forum, show the proper washer “stack.”

Washer stack for DM6A distributor points

Healey points setup

 

Coil

Rather than the original Lucas Coil, or Lucas Sports coil, I decided to go with the Pertronix Flame Thrower Coil in the Bloody Beast. The coil was originally mounted on top of the generator, but since I am using an alternator, that mounting position was not available. I mounted the coil on the vertical upright shroud support post.

Pertronix Flame Thrower Coil

Pertronix Flame Thrower Coil

 Ignition Wiring

To complement the Pertronix Flame Thrower Coil, is used Pertronix ignition wiring as well.

Ignition wiring

Ignition wiring

 

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