MGB - Electronic Ignition

It was an unseasonably cold weekend recently. Since Oliver is in a nice warm-ish garage and Spring is supposed to be here now, I decided that I would start getting Oliver (1978 MGB) convertible-top-down, road-ready. Today's post starts us off with replacing the ignition. Like so many things with these old cars, nothing is as simple as it seems on it's surface, so this post ends without a running car. Maybe I'll get it next time. 

AccuSpark

Most folks think of "Pertronix" when they think of an electronic ignition upgrade. PerTronix makes great electronic ignition systems, for sure. I ran one on the old bus engine for a little while. I decided I would try the AccuSpark system because it was less expensive and appeared to be UK-based. The UK-based nature had me thinking that maybe it was better suited to an English motor. So, back in the Fall 2019 when I was thinking that I would be spending the winter finishing Oliver, I bought one of their kits, and put it on a shelf. Things happened, CoViD-19 blew up, the wiring in Hapy got complicated and I forgot about it... until I was cleaning my garage and found the box with the international shipping labels still attached. Jeez.

For around 70 pounds plus postage, you can order a drop-in ignition. When I did it, it ran me about $150US including shipping to the States. So, what's in the box?

- a pre-fitted electronic ignition in a 45D distributor (correct dizzy for a rubber-bumper / later model MGB)

- a distributor cap

- 4 Champion AC9C 3-prong spark plugs

- a blue ballast coil (though you can upgrade to a "Viper Dry" coil)

- a set of spark plug leads ("wires" to US folks) with a di-electric grease pouch

- you can optionally include a timing light

Preparation

It is recommended that you set your engine to top dead center (TDC) or firing position for the #1 cylinder. For most cars, the distributor could go in multiple ways, so making sure it is oriented correctly requires that you know which cylinder is ready to fire. The MGB engine is unusual in that it has a one-way-only key in the distributor drive and corresponding gear in the engine. If you try to put it in any other way it will not seat and not turn. Still, I wanted to make sure I had clear timing marks so I got a 1-15/16" socket for my 1/2" ratchet, removed the air-directing tin between the front of the engine and the rear of the radiator and turned the engine (clock-wise) until I could see the little nick on the rear of the main pulley. I aligned it with the top-most saw-tooth on the timing meter and then marked both with a dot of yellow paint. I also marked the tooth representing 15* advanced, since that is the stock amount of advance desired at idle (per the Bentley manual). This mark later turned out to be incorrect.

 

To find true TDC, I had to pull the valve cover and watch the valves move while I rotated the engine with the 1/2" ratchet. The mark that I believed was TDC was about 90* off. I found a different mark on the front (front is front) of the main pulley that was around midway between the points where the intake/exhaust valves opened. Accepting that this was the true TDC, I marked the nick with a dot of yellow.

With the replacement kit and tools on a nearby table, and the radio playing the Saturday morning KBOO shows, I was now ready for some ignition fun.

Spark Plug Remove and Inspect

My old ignition basically had not been looked at since I bought this car. Since Oliver has not had more than a couple hundred miles on him, clearly I did not drive his old system into it's current state. Frankly, it sat for a few years before I bought him, and without any servicing since, my expectation was that it needed, well... a lot. His performance had not been all that great when I bought him, and the new exhaust did not create the pick-me-up I had hoped for. So, away we go.

I started with removing the old spark plugs with a 13/16" socket. Spark plugs are a great gauge for how well your combustion has been performing: too rich, too lean, oily, too hot, etc. My findings were mixed, and odd. From firewall to fan, Plugs 4 and 3 were black, but dry, indicating that they had been burning inefficiently. Plug number 2 was black as well, but had some soot on it. Plug number 1 had a little bit of soot around the edge, but the prong was grey. So, I look at my plugs and compared them to the AutoLite Plug diagram (image posted here) to try to figure out what's going on.

Based on the mapping document here, numbers 3 and 4 are "carbon fouled", with lots of possible causes, ranging from "wrong plug" to weak ignition to mis-tuned carb, too-gentle driving or a bad choke. Neat, but at least they look like twins. I am more concerned about plugs from 1 and 2. These are fed by the same intake runner, yet they look very different. Plug 2 looks like a worse version of plugs 3 & 4, and plug 1 has a clean or normal looking ground electrode with some carbon around the edge.

L-to-R: plugs 4 to 1

These plugs may have been wrong for the engine. Spark plugs are a religion, and I have followed a relatively simple rule (that will probably frustrate / anger / enflame some people): I align the plug manufacturer country with the engine/car manufacturer country. So, I'll find NGK's for our Subaru, Bosch for Audi/VW's and Champions for US/English cars. The plugs I pulled out are single-prong NGK's; to be fair, NGK may make a perfect plug for the MG. I don't know. I can say that the AccuSpark folks (from the UK) sent me 4 Champion AC9C 3-prong plugs. MAybe they subscribe to the same flavor of spark plug religion that I do. I don't expect the plugs were the problem, but they may have been a contributor. Regardless, I gapped (0.035" per the Bentley manual) the three prongs on each plug and then installed the delivered-with-the-kit spark plugs.

Dizzy Swap

With the plugs done, I pulled the distributor cap and the lead from the coil. This created some access to the distributor mounting bolts. The prior owner installed a remote inverted oil filter unit, so the access to the front mount bolt was still a little challenging, but not impossible. Still, a little fun with an old-skool 7/16" spanner got the bolts out. Once the bolts were removed, the dizzy popped right out. I immediately settled it back in, and made a mark in the dust on the starter cover which direction the rotor was pointing. As I said above, the dizzy can only go in one way, so whichever way the rotor is pointing when you pull the cap is the only way it could be pointing. In the images I have seen on the internet, the number 1 plug is usually in the 1 o'clock position, but that is not always the case. Sometimes the dizzy gear is put in upside down so your #1 plug position is actually on the bottom. When I rotated the engine, the cap was on, and the leads had not been touched. I noted at this point, though, that the distributor rotor was pointing down and slightly to the left. When I removed the cap, the #1 lead was in that area, so I figured I would put it back together the same way. If things were 180* off, it will run, but poorly. Re-setting the leads 180* the other way would be easy to test later. I took the picture below so I could run the replacement leads the same way as they were.

old leads

With the old dizzy off, I loosened the clamp on the new one so it would move a little bit. The timing of the old set up might have been off, based on the "carboned" color of the plugs. Regardless, I want to be able to change it from the shipped-to-me state. I will clamp it tight (5/16" wrench) once the timing is verified. Satisfied that the dizzy would turn in the clamp, but only with some effort, I popped the new dizzy into place. The new mounting plate only had a single bolt hole for mounting, above and to the left, but otherwise, install was trivial. The lower bolt was the hard one to get to, so I was not going to complain. I put the now-extra bolt into the lower right hole anyway and snugged them both down tight.

Coil

The kit delivered with a new coil that corresponds to whether there is a ballast in your system. The electronics require the more powerful coil. Swapping a coil is easier than swapping a distributor, usually. In this case, because so many things leverage the mounting bolts for a ground, it is more of a juggling act than the coil swap in the old bus. I unmounted the original, and set it upright on the starter, leaving the wires attached to the various tabs. This gave me room to install the new coil and remain focused on the grounds and such. Once in place, I moved the female wire-disconnect-tipped wires from old coil to new coil.

Cap and Leads

The hard part, if you want to call it that, was over. Now, it was a simple matter of installing the leads. The prior set-up had the #1 lead around 7 o'clock. From there, they run the same way on all MG's: 1-3-4-2 anti-clockwise. The set of leads delivered with a clear dielectric grease, which is recommended on the electric connection to prevent corrosion and encourage a better current delivery. I smeared some on each end of all connections and plugged things in nice and snug. The electric connector floated around in the spark plug boot end a little bit so I made extra-sure the encased metal spark-plug end was definitely snapped on.

At this point, I would have started the engine and set the timing. Unfortunately, the turn of the key resulted in nothing. No noises, no clicks and definitely not starting. A quick glance at the voltmeter told me all I needed to know: flat battery. Awesome. So, this post got kinda long, and the resulting diagnostic did as well. So, I'll get back to Oliver next time. Thanks, as always, for following along--