Moke Ignition & Timing
I knew nothing of timing when I commenced re-building my Moke. I now know a lot more after a few somewhat major issues during my re-build. The first thing I did was replace the timing chain with a double row kit. The below image shows the difference between the two kits. Original single-row chain on the left, newer double-row kit on the right.
The fitting of this required that the radiator be removed and some some minor fabrication to fit on my engine. The first step however is to get the engine at Top Dead Centre. The easiest way is to use a mirror and line the pointer up in the peep hole on the clutch cover with the 1/4 mark (assuming the engine is already aligned). You can also tell that you are approaching TDC by watching the rockers for cylinder no. 4 (left hand cylinder as if you are looking at the engine from the front) and moving the engine until they are on the rock. This means that they both hit the top and change direction. Once you see this, you should be near enough top dead centre and should be able to see some markers in the peep hole.
The first step of the fabrication was to belt out a small indent that exists in the A+ series timing chain covers. I don't believe this is an issue on the A series engines. The below images show this:
The next step was to replace and countersink two of the screws that hold the front plate onto the engine. This is necessary as the double row timing chain is much thicker than the standard timing chain. I used a simple countersink bit on my drill press and was about 5 mins work...easy enough
This mod was fairly straight forward and will last a lot longer than the standard timing chain and help to minimise chain stretch. It is very important that when fitting a timing chain that when the engine is at Top Dead Centre (TDC) that the divots on the sprockets line up. There is no negotiation here, trust me....I learnt the hard way and had to dismantle everything again to get it going properly.
A good tip is to fit two gaskets to the timing chain cover. The cover is inherently flimsy and can warp quite easily in turn leading to oil leaks. I fitted two gaskets here and I have not a drop of oil to be seen from this cover. The gasket for the front plate also naturally needs to be changed when removing it from the engine. This however only requires one gasket as it is much more sturdy that the timing chain cover.
Next was the ignition timing. I purchased a new up-rated Lucas ignition coil for my engine also to ensure that I had a nice strong spark. One thing I learnt here is that you should never leave your ignition on without the engine running for long periods of time. This can lead to melting your coil and if you have the oil filled type, can create a nasty mess. Play it safe and turn your ignition off when the engine is not running. This was very simple to fit and it came with the required mounting bracket.
Setting the ignition timing consists of two steps. The first is to set the ignition timing statically, followed by strobed timing (also known as dynamic timing) using a timing light. Static timing is used to get the engine running correctly so that the the strobed timing can be set. Strobed timing is for fine tuning (and it makes all the difference to performance).
Static Timing: To set static timing, align the engine up to approx 5-7 degrees before top dead centre (BTDC). You can do this in much the same way as getting your engine to TDC as per the above instructions however you then move the engine just a little bit further to put it between the 5 and 10 degree marks on the flywheel. Once you have this set, put the handbrake on to prevent that car from rolling and moving the valves. Now take the lead off cylinder no. 1 (closest to the radiator) and put a screwdriver in it and place it near an earth of some sort (e.g. a thermostat housing bolt). Now loosen the distributor until it can be rotated, turn the ignition on and rotate the distributor until you get a spark. At this point, you should tighten the holding bracket for the distributor back up and voila! Static timing is set. Note, you may need to rotate the distributor back and forth a number of times to get it in the right spot. This should allow you to start the engine.
Dynamic Timing: This is fairly straight forward if you have a timing light of and you know the timing specifications of your engine at its factory idle speed. This is usually in the manual however as I didn't have this handy for my engine, I needed to do some scouting around. It turns out that the ignition timing for my engine should be set to 10 degrees before top dead centre (BTDC). On the A+ series engines, there is a series of teeth spot welded onto the timing chain cover. In addition to this, the harmonic balancer has a notch in it to use as the timing point. See here:
When the notch on this pulley lines up with the longest one of these teeth (the top one) then the engine is at TDC. It also turns out that the fourth tooth from the top on my engine represents approximately 10 degrees BTDC. I found this out by lining the 10 degree mark on the flywheel and then finding out which tooth was adjacent to the notch in the balancer. Easy enough?! This however is slightly more difficult on the A-Series engines when these teeth do not exist. The easiest way around this is to use a marker or chalk and mark a spot on the timing chain cover and a matching spot on the balancer when the flywheel is set to the relevant timing specification for your engine.
Once you have these reference points marked, attach the timing light to lead number 1 (the cylinder closest to the radiator). If your distributor has a vacuum advance fitment, this needs to be disconnected at this time and the vacuum port on the carburettor or intake manifold must be blocked. This will be reconnected at the end of this process. Now run the engine up to operating temp and at the factory idle speed. The distributor will need to be loosened enough so that it can be rotated as was done in the static timing process. Point the timing light at the markers that were made earlier and rotate the distributor until these line up. Now tighten the distributor and re-connect the vacuum advance and you're done.