centrifugal advance checking gauge
videos at bottom of the page
how to check and set the centrifugal advance mechanism on all A series engines.
You may want to check and adjust the centrifugal advance mechanism. You can use an adjustable stroboscopic timing light and a tachometer, without dismantling anything. If these items are not to hand then a different method, shown here, will suffice and then set up your contact breaker, points box.
Set your points correctly, by either using a dwell angle meter or a timing bulb or the traditional feeler gauge method. Here is how to check and adjust the centrifugal advance mechanism and the operating parts.
The tools needed are a needle pointer attached to the cam lobes and an inscribed checking gauge, attached to the crankcase. There were various A series engines and all had different advance curves. The maximum advance on a A53  and an M4  engine is 8 degrees, for the A79/0  it is 12.5 degrees and finally for the A79/1, M28 and the M28/1 [all 602] the advance is 15 degrees.
On one side of the gauge 6,8,10,13 and15 are stamped, on the reverse side is stamped the engine types and the maximum advance for each type.
There is a zero line, which the pointer must match up with and small cut outs for each different angle of advance. There are 4 small cut outs, 0 line, 8, 13 and 15 degrees.
Attach the gauge to the crankcase and mount the pointer [see video]. There is a step on the gauge which must be secured into the recess. Before tightening the setscrew, pull the tool to the left, so that it fits the crankcase circumference and then lock it. Turn the flywheel to place the pointer in line with the zero line. The cam lobes are fixed to the camshaft and are able to rotate slightly to allow the centrifugal advance to occur.
These photos show the mechanism parts. The weights, the leaf springs and the limit stops. There are 2 each of these items.
Once you have set the tool to the zero line, turn the advance mechanism forwards and backwards a few times and release it. It should always return to the zero line. If it doesn't, then, new leaf springs may be needed. Simply turn the pointer anti clockwise and read off the advance in degrees. If the correct reading is not obtained, then simply use a small pair of pointed pliers and either bend the limit stops up or down. They must be equally spaced. Spreading them up increases the angle and vice versa.
You can use this method with the Lumenition electronic unit but other systems have their own advance methods inbuilt.
These tools can be hired or purchased.
Centrifugal advance. Part 1.
Centrifugal advance. Part 2.