XJ6 4.2 1984 series 3 ignition timing.

[richardpowell01226]

Hi my name is Richard I have a 1984 XJ6 4.2 series 3 I have an Hayes manual and the ignition timing setting states 6 degrees before TDC is this with vacuumed connected or not. Also on a google forum it says 17 degrees before TDC North American models, could someone please clarify which setting is correct, with or without vac and rpm. Please could someone help confused . Com
Kind regards Richard.

[mike020150]

Hi Richard,
I have a copy of the Haynes manual which although dated 1981 may hold clues as to what is causing the confusion. The manual notes that there were two distributors fitted to North American models, the 45DE6 and the 43DE6 which was fitted to California cars only. The 43DE6 does not have a vacuum advance module fitted to it so, unlike most XJs, on California cars it is not necessary to disconnect any vacuum lines to set the timing. It is on all others.
All 4.2 litre models require an 8 degree static ignition advance setting but setting the timing statically is not ideal. It's better to set it dynamically, i.e. with the engine running at speeds above idle. According to Haynes, the XJ dynamic settings are:

10 to 15 degrees before top dead centre (BTDC) at 1400rpm
22 to 26 degs BTDC at 2500rpm
30 to 34 degs BTDC at 5000rpm

Over time, wear may mean that it's not possible to set the timing statically to 8 degs and still achieve readings within the dynamic ranges quoted. In that case, aim for readings in the dynamic ranges because those settings will give the best on-road performance even if at idle all is not absolutely ideal. Mike.

[richardpowell01226]

Cheers Mike for your reply I will try your recommendations, thank you very much for your help.