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ignition timing and modern petrol?
Posted: Thu Jun 16, 2011 8:14 pm
by jcrtd
Hi all
Just wondered if the ignition timing stated in the book, 4 degrees BTC, still applies when using the petrol avaiable at todays filling stations. The engine is 803cc Series 2.
John[frame]
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Re: ignition timing and modern petrol?
Posted: Thu Jun 16, 2011 9:32 pm
by bmcecosse
Forget about 'the book' - advance it till it pinks in top gear when accelerating - then retard it slightly so it's 'not quite' pinking. Actually - a very slight transitional pinking as you put your foot down is fine - it's just the vacuum advance backing off. But you must never allow continuous pinking.......
Re: ignition timing and modern petrol?
Posted: Fri Jun 17, 2011 4:59 pm
by jcrtd
Thanks for the reply. I started with the timing at about 6 degrees BTC and when the book said 4 I thought it wouldn't be right way based on performance so will take your advice and adjust as suggested.
John
Re: ignition timing and modern petrol?
Posted: Tue Jun 21, 2011 7:44 pm
by faversham999
I tried the bmcecosse way
on a 948cc it goes great as I do not normally do repairs,so I had it cheked by a friend with a strobe It was 7 degrees btc perfect.
Re: ignition timing and modern petrol?
Posted: Wed Jun 22, 2011 9:34 am
by rayofleamington
On an 803, you would be unwise to take the timing up to borderline pinking!
I do 6 degrees on a later A-series and would probably do 5 degrees on an 803.
Petrol octane rating is better than when the 803 was made so a slight advance should be no problem - however the engine is not strong and as they are few and far between it's probably best to go safe and use at least 1 degree less than borderline pinking timing.