LEYLAND PRINCESS TIMING TROUBLE
Q I have what I hope is a simple question for you to answer. I wish to check and if needed adjust the ignition timing on my 1976 Leyland Princess 1800. I have located timing marks on the front cover behind the crankshaft pulley, but these are just a series of pointers with no indication as to what they represent. As I intend to use a timing light, I would like to ensure I am carrying out the process correctly and hope to cure the light pinking that I have been getting lately when labouring up an incline. Any advice you can give would be greatly appreciated. Joseph Platts
A The timing marks you have found are in increments of 5 degrees, and the setting is read off at the base of the triangles with the TDC mark at the last clockwise tip of the triangle. Reading from left to right (clockwise) the first indent is 20 degrees, then 15, 10 and the last is 5 degrees. The timing on your car should be set at 10 degrees at 1000rpm, without the vacuum advance fitted.
When checking the timing with the strobe, you should also check that the ignition advance is operating correctly – the timing should advance by 2-6 degrees at 1200rpm, then advance to around 10-14 degrees at 2200rpm and finally 24-48 degrees at 4400rpm. To check the advance at the higher speeds you would need a timing light that was capable of being adjusted and so zeroed in on the TDC mark.
Once the timing is correct, the engine tick-over speed should be adjusted to 750rpm. I would also check the valve clearances before commencing the timing check as this will ensure you are working at the best conditions. The clearances on both the inlet and exhaust valves should be 0.33mm and they should be checked cold.