I’ve always appreciated the advantages of electronic ignition, so when I recently acquired a ’71 Berlina, I decided to replace its breaker points-based ignition with a more modern electronic unit. In the past I’ve installed the Marelli-plex unit, which was designed for and fit just about any four-cylinder Alfa back to at least the mid-sixties. Alas, the Marelli-plex is no longer available and its replacement, the Ricambi-plex (from Alfa Ricambi (800)-225-ALFA) is $295, more than I wanted to spend. In addition to cost, I wanted to keep the original distributor with its original ignition advance curve. (The Marelli-plex included a new distributor which had its own, slower advance curve.)
There were two possible systems in my price range (less than $100), 1) the Crane Cams/Allison XR700, which is optically triggered ($86 from Imparts), and 2) the Pertronix Ignitor, which is magnetically triggered ($70 from various sources, 1-(800) 827-3758). I chose to install the XR700 in the Berlina, but next time may chose the Ignitor since it looks easier to install and doesn’t require an external control box (everything is installed in the distributor, out of sight). Major advantages of an electronic ignition over a points-based ignition are:
1) Put a mark the distributor body below the number one spark plug terminal, then remove the distributor cap.
2) Engage fourth gear and push the car until timing mark “P” (TDC) on the crank pulley is aligned with the timing pointer and the tip of the rotor is pointing towards the mark you just made on the distributor body.
3) Caution: Disconnect battery ground cable before continuing.
4) Remove the distributor from the engine. (In loosing the 10mm clamp nut, it helps to have the special distributor wrench available from various Alfa suppliers.)
Initially I thought I could install the trigger module into the Bosch JF4 distributor that came with my ’67 Duetto, but after an hour or so of trying I decided there just wasn’t enough room. So, I decided to install the unit in the Berlina’s original Marelli distributor.
(See last section of this article for Bosch JF4 distributor installation instructions.)
Unfortunately, installation into a Marelli distributor is a bit more complex, because the distributor has to be taken apart to mount the optical shutter on the points cam--see Figure 2.
With most “normal” distributors, mounting the shutter is easy, just remove the rotor and push on the shutter, but since the Marelli has its advance weights mounted above the points, the distributor has to be disassembled.
5) Mark the drive dog and distributor body so the distributor can be reassembled correctly--see Figure 3.
6) Remove the spring, locating pin, shims, and sealing washer from the drive dog. (Make a note of the removal order so everything can be returned to its correct position on reassembly!) Remove the distributor shaft from the body.
7) Remove the rotor (for better access), breaker points, condenser, and all wires from breaker points to coil or ground. Do not damage the rubber grommet through which the wire exits the distributor.
8) Attach the optical trigger to the mounting bracket. To allow vertical adjustment of the trigger, do not tighten screw completely. Then use an existing screw to mount the trigger assembly to the breaker plate — see Figure 4. To allow adjustment, do not tighten the screw completely.
9) Clean the points cam with carb cleaner and dry it thoroughly. Select the best fitting 4-slot shutter supplied with the installation kit. Slide the shutter onto the distributor shaft points cam until firmly seated and level. If the shutter is a loose fit, apply several drops of Super Glue. Make sure that the flats inside the shutter line up with the flats on the points cam.
10) Reassemble distributor in reverse order of step 6.
11) Pass optical trigger cable through exit hole used for the points wire.
12) Adjust optical trigger height to locate shutter rim 2/3 from top and 1/3 from bottom of the optical trigger opening as shown in Figure 5. Make sure the shutter is level and can spin without interference. Figures 6 and 7 show the Marelli distributor with the trigger module installed.
13) Reinstall the distributor. Be sure to align the marks you made in step 1.
14) Mount the gold-colored ignition module on the firewall or fender well. Avoid locations exposed to high heat or water. Do not mount it on the engine. Make sure wires from the module can reach the coil and distributor.
15) Refer to Figure 1 for wiring information.
16) Connect the ignition module’s black wire to the chassis or engine block.
17) Connect the ignition module’s yellow wire to COIL- and the red wire to COIL+. (On Bosch coils, COIL- is “1” and COIL+ is “15” and on Marelli coils, COIL- is “1” and COIL+ is “16”.)
18) Insert the three terminals on the end of the cable from the optical trigger assembly into the Molex plug supplied with the installation kit. (Make sure the individual wire colors match.)
This adjustment procedure insures that the rotor is pointing directly towards a spark plug terminal when a spark is produced. Correct alignment assures maximum spark energy by reducing the gap between the rotor tip and cap terminal.
19) Remove the high voltage coil wire from the center distributor cap terminal and place the tip of the wire ca. 3/8" from the engine block for spark testing. Tape it down. Do not hold it with your hand.
20) Reconnect the battery and turn ignition key on, but do not crank engine. (Timing marks must remain aligned.)
21) Slide trigger assembly around the edge of the shutter in a counterclockwise (CCW) direction. When the light beam from the optical trigger reaches the leading edge of a window in the shutter, a spark will fire from the coil wire. When the spark fires, stop sliding the optical trigger and tighten all screws to maintain this position.
22) Attach the optical trigger cable to breaker plate with a nylon tie wrap. If possible, use the original rubber grommet to seal the cable exit hole, otherwise, use silicone sealer.
23) Reinstall the rotor. Momentarily crank engine and visually check for clearance around all parts. Make sure that the shutter is level and does not wobble as it turns. If the shutter rubs the optical trigger, adjust the mounting arm. Reinstall distributor cap.
24) Start your engine and set ignition timing according to specs. Note that dwell meter readings are meaningless and should be ignored.
1) Use optical shutter #220. Because the rotor fits over the points cam slightly, the shutter must be modified to fit down over the points cam. Remove the four plastic tabs at the top of the shutter with an Xacto knife or razor blade (see Figure 8). Do not remove the plastic "bumps" that orient the shutter.
2) When I used the existing points mounting hole to install the optical trigger, after
performing the optical trigger adjustment, the trigger was at the end of its travel
limit. I therefore decided to drill a hole in the distributor base plate
for greater mounting flexibility. To do this the base plate must be removed:
There are a few things to watch out for here:
3) Reinstall the base plate into the distributor.
4) Install the optical trigger and shutter at the same time.
5) The trigger will potentially interfer with the screw that holds the rotor in place. There are a couple things to do to help eliminate this problem:
6) Do optical trigger adjustment as explained above in steps 19) through 24).