Not only is the original "OPUS" Lucas ignition amplifier junk, It's location defies logic. It's installed on the engine in the middle of the engine "V" where the engine temperature is at it's worst. This amplifier was later redesigned by Jaguar with longer leads so the location could be moved off the engine, but these amplifiers continue to fail. After replacing the original and redesigned amplifiers I decided that the permanent solution was to install an aftermarket unit manufactured by Allison. (Allison was later acquired by the electronic division of Crane Cams). Note that the Allison/Crane ignition amplifier was also designed to be installed inside the engine compartment. This seemed like a recipe for disaster. Very few, if any, engine compartments get as brutally hot as the Jaguar V-12. My solution, mount the ignition amplifier inside the car!
I chose the Crane XR700. The schematics (photographed below,) detail the installation. (An addendum clearly states that the trigger unit must be maintained.) There is also a diode supplied that may or may not be necessary to have the tachometer operate properly. This will be addressed later.
Remove the distributor cap. I strongly recommend tagging the spark plug leads. Now is a good time to check the vacuum advance mechanism. This mechanism is prone to seizure.
Pictured below is the Crane replacement amplifier and associated parts.
Assemble shutter wheel to device that fits over distributor shaft.
Shutter wheel, trigger and amplifier.
As the shutter wheel passes thru the optical trigger it signals the amplifier.
The unit comes with a number of useless brackets that's designed to mount the optical trigger in the distributor.
I found these brackets to be totally unsatisfactory. I fabricated a bracket from sheet-metal stock that met my requirements (red arrows).
Install fabricated bracket, 12 window shutter wheel and retaining "C" clip.. (blue arrows). Attach optical trigger to bracket. (red arrow).
Install trigger unit. Be prepared for one or more of the special plastic screws (red arrow) to break. Replacements on hand before attempting this project is recommended.
The photograph below shows the plug from the optical trigger.
I used a generic plug and silicone sealant to augment sealing where the wires passed through the distributor housing. (The Crane unit comes without a plug).
This project was to install the amplifier inside the car, away from the hostile environment of the engine compartment. To accomplish this the glove box had to be removed.
Disconnect the battery. Using a 1-inch drill bit, drill a hole from inside the car through the firewall. The hole must be large enough to pass the plastic plug through. If necessary, you can use a smaller bit and massage the opening with a round file.
Great care must be exercised here. The object is to exit just below the 12-volt rod that runs across the firewall. If necessary, drill a small pilot hole first.
Measure carefully, therapy awaits you if you screw this up.
The amplifier wire length is critical. It determines the final location of the amplifier inside the car. Also note the red and yellow wires. They will be connected to the coil.
Route the amplifier wires beneath the intake manifold. This represents the shortest distance to the distributor.
Connect the amplifier plug to the optical trigger unit plug from the distributor.
Install amplifier onto the heater/AC side support. The amplifier mounting holes were not in the right location, so I fabricated a base.
Connect the red and yellow wires to the coil.
The tachometer requires a diode to be installed in the sensing wire. (Crane supplies this diode.) Once connected I used a large heat shrink tube to secure the connection.
The glove box will fit without modification, however it rests against the amplifier. I wanted a minimum of 2 inches clearance around the amplifier, and the ability to remove the amplifier without removing the glove box. To accomplish these goals I modified the glove box as per the photograph below.
Glove box and amplifier installed. Note additional clearance. Heat will never be a problem for the amplifier.
Problem solved. Project complete. Glove box installed. I covered the modification with leather to match the inside of the glove box compartment.
