Ignition timing may sound like a rather complicated matter but it is really very simple. Get it wrong though and your engine will suffer
It cannot be emphasised enough how important correct ignition timing is for the VW air-cooled engine, not only in terms of smooth running, but also in relation to engine longevity.
The ignition timing is controlled by the orientation of the distributor body to the distributor shaft. This shaft is in effect a cam, and controls the opening of the ignition points, which, in turn, trigger the sparks to each cylinder. By rotating the body, the point at which the spark occurs during the piston stroke is altered. By advancing the timing you cause the spark to occur before the combustion chamber is at its smallest volume, retarding it does the opposite. Advancing the timing can be beneficial, up to a point, allowing the fuel / air mixture to ignite more completely and produce a more efficient burn, but take it too far and problems can occur. These problems are fairly complex, but will result in detonation – definitely not a good thing. In basic terms, detonation is where the flame front in the cylinder jumps ahead of itself, igniting the mixture randomly across the cylinder. This causes a large amount of heat and is one of the number one causes of overheating in air-cooled engines.
So lets get started…
The first thing you need to do is to rotate the engine so that the #1 piston is in firing position and your crank pulley is lined up to the crank case.
The crank pulley has a notch in it. This indicates the static timing point and should be aligned with the join between the two case halves (see photo above). If your pulley has two notches, line it up with the one to the right, if three it’s the middle notch.
Now remove the distributor cap. The metal part on the rotor arm should be pointing toward a very fine line/mark on the edge of the distributor body (see photo above).
I say “should” as this really depends on whether the distributor drive gear has been installed correctly (that’s a whole other tech article).
Basically you should have something like this (fig 1):
But you can also align the notch in the crank pulley and discover the rotor arm is pointing 180 degrees in the opposite direction (fig 2). Fear not! Your #1 piston isn’t in the firing position, but #3 is. Simply rotate the engine so the crank pulley goes through 360 degrees (1 full rotation) which will bring the rotor arm into the right position. Remember to align the crank pulley to the case again.
Now locate that line/mark in the distributor body again. This needs to line up perfectly with the centre of the rotor arm. If it doesn’t (it probably won’t if you have removed/replaced the distributor), you need to loosen the 10mm nut that clamps the distributor in place (see photo below).
Once loosened, the body of the distributor can be rotated by hand (shown below) so the mark in the distributor body lines up with the centre of the rotor arm. This is your static ignition timing, which on a stock engine is seven degrees.
Now remember to tighten that clamp back up and pop the dizzy cap back on.
That wasn’t too daunting was it? No, of course not.
Static timing your air-cooled VW this way will get your engine running but you will still need to tune it further by using a timing strobe. You can see how to do that here: Timing with a strobe