Previous owners had slowly converted the Elan’s Twin Cam to non-Federal spec. The secondary throttle assembly was removed, a custom carb adapter replicating the non-Federal version was installed, the vacuum retard mechanism was disabled, the Strombergs were converted to adjustable needles (although strangely keeping the leaner Federal profile), and the exhaust manifold was replaced with a header from RD Enterprises. The two items remaining were the distributor (specifically the advance curve) and the mixture needles. The Federal engine uses a very, very conservative advance curve that ranges from 5-19 deg with max advance at 5000 rpm vs. the non-Federal curve's 9-33deg with max advance at 6500 rpm. Further, the carbs had fixed mixture needles to prevent Joe Mechanic from messing with emissions, and those needles had a much leaner profile than used outside the US.
Options to correct the ignition advance included sending the distributor out for a recurve while keeping the Pertronix, converting to a 3D ignition system which would yield improvements to drivability and give great flexibility for future mods, or use a programmable distributor from 123 Ignition. Their Tune+Bluetooth version includes a rev limiter, phone-based anti-theft system, vacuum advance, and customizable advance and MAP curves with up to 10 user adjustable points. It’s not fully 3D, but one could argue it’s 3D-light, or perhaps just 2.5D. Installation is also very easy as everything is contained within the distributor and requires just one additional ground wire compared to the Pertronix. In contrast, the 3D system meant building a wiring harness, replacing the crank pulley with one that includes a trigger wheel (requiring radiator removal), mounting a crank sensor, finding a location for the ECU, EDIS (or a more expensive ECU that doesn’t require one), and the wasted spark coil pack. Bottom line, it’s a PITA. Given I was trying to avoid PITA, and I prefer keeping the engine bay aesthetics close to period correct, I opted for the 123 Ignition.
On the surface completing this work seemed pretty simple, but the project was plagued with issues ranging from parts delivery to my carelessness which nearly turned the Elan into a rolling candle. First, the parts order. We had a big snow storm in the area that delayed delivery of the distributor by a week. Once it arrived, it was immediately apparent they included the wrong cap. Rather than the Twin Cam required side entry version necessary for carb clearance, they supplied a top entry cap. Fortunately the vendor was very responsive and sent out the correct cap the same day I contacted him, but two more snow storms added another week and a half to that delivery. Once it did a arrive I began removing the old distributor and had the revelation that the original distributor cap uses a screw in style plug wire, versus the more common push on style as found on the 123 Ignition. In other words, new plug wires were required to complete the installation. Add another week and a half for Magnecor to make and ship the new set, and I had lost almost a month.
This is where the next set of issues arose. The ones due to my impatience and stupidity. First, I screwed up and attached the distributor’s ground wire to what I thought was a ground. Actually it is a ground whenever the starter isn’t engaged (as in when I tested it with a voltmeter) but since that lug also served as the other side of the solenoid, it became hot when the solenoid closed to spin the starter. As a result, the engine wouldn’t start until after releasing the key from the start position when the ground was reestablished. Fortunately that fix was simple; find a constant ground. With that corrected, the engine started and the first test drive ensued. At this point I should mention that my plan was to program in the Federal ignition curve, then after installing the richer needles, program in the non-Federal curve. Given most people advance the Federal distributor a few degrees, I bumped the initial curve by 3 deg, but it was still pretty retarded. Although the engine seemingly ran fine, after about 3 miles, the cabin began to fill with smoke as I pulled away from a stop sign. That did not inspire confidence, but it did inspire panic. Turns out the header was getting extremely hot and burned a hole through the adjacent fiberglass footwell. The cause? More stupidity on my part. The 123 Ignition instructions state to set #1 at TDC, then with the cap removed, rotate the distributor in the opposite direction of normal rotor rotation until a green LED on the face of the distributor just begins to light. Easy. Well, easy if you don’t rely on memory for the normal rotor rotation direction and that memory is wrong. The result is that the distributor thought it was just entering the window when the rotor completes the circuit for a cylinder, when in fact it was just ending that window. The result was a weak spark that allowed unburnt fuel to enter the header and ignite, thereby significantly increasing primary tube temperatures and burning the fiberglass just 5/8” away. Oops.
With that solved (and a heat shield installed between the header and footwell), the engine ran normally albeit just a bit smoother. Next up, swapping in the richer, 2BAR needles, and programming in the non-Federal curve retarded by 2 degrees to account for fuel quality. This was a big improvement. Power seemed a little better – nothing radical, but enough to be noticeable – and throttle response was significantly improved. The two-step delivery upon hard throttle application that felt similar to a modern turbo, was gone. It still isn’t razor sharp like DCOEs or an ITB setup on a fuel injected car, but it now feels normal and no longer calls attention to itself.
Next up is enabling the vacuum advance functionality. The plan is to get some miles on the engine without the vacuum advance to establish a baseline for drivability and fuel mileage, then hook it up to identify any improvements or setbacks.