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Ignition Timing

Posted: Wed May 05, 2021 10:10 am
by Joe
Have been doing some tunning and was wondering what is the optimum timing, seem to be a few depending where one looks. Have a 77 2500 TC Australian car, no egt and electronic ignition. Thanks

Re: Ignition Timing

Posted: Wed May 05, 2021 4:18 pm
by Mike Stevens
Probably best to start with the book setting and then advance/retard until the engine just doesn't pink under high throttle load at low engine revs. If it doesn't pink, advance it a bit until it does, then retard it until it just stops.

The problem with just using the book setting is that it would have determined over 40 years ago when petrol was a different mix.


Re: Ignition Timing

Posted: Thu May 06, 2021 9:51 am
by Joe
Thanks, but that is my first problem some books say 8 BTDC, others 10 BTDC. Have tried both and it starts better on 10 but other than that hard to tell.

Re: Ignition Timing

Posted: Thu May 06, 2021 12:20 pm
by Phil T
As Mike says, book timing values are now redundant as the fuel now is nothing like the fuel of the 60s/70s.

Get it started and do the pinking tests to get the best settings.

Fortunately this means driving it!

Re: Ignition Timing

Posted: Thu May 06, 2021 12:25 pm
by Charles H
A 1977 2500 with the 45D distributor would be 10 degrees BTDC. Pre 1973 was 8 degrees.

Re: Ignition Timing

Posted: Thu May 06, 2021 2:22 pm
by Alec
Hello Joe,

another point regarding this subject; our cars are now pretty old and over the years the distributor may have been changed to a visually similar but with the wrong specifications for the engine. The workshop manual, if you have one gives the correct numbers, this can be found stamped on the body of the distributor and on the vacuum advance module, either or both could be wrong.
Although the fuel has changed the advance curve is, I believe, more of a factor of the engine specification, so it's worth a check

P.S. From the club service notes the correct distributor for a 1977 2500 TC and S is :- 41624, but it doesn't give the vacuum module number.

Re: Ignition Timing

Posted: Sat May 08, 2021 12:09 pm
by Joe
Thanks, rechecked timing and went from 8 to 10 btdc starts and runs well with no pinging. So will run it for a while and then see whether it can be improved, will look at Distributor but I put a new one in about 18 mths ago it was a Powerspark 45D6 supposed to be the right one. Also has a Lumination MTK009 ignition. Which when I put them together the Dist cap would not fit so had to grind down the Rotor arm for the cap to sit properly. Don't think it affected anything as car ran well afterwards.