Ignition Timing

[kevinw]

We not had a dumb question from me for a while, so.......

I've aquired a Xenon timing light and want to confirm / check the timing on my 2000. The pulley with the timing marks on it appears to only have a mark for (presumably) tdc, but I need to check more carefully as the manual suggests that it should be marked with tdc and a selection of btdc and atdc markings. It is a pain rotating the engine because it is an automatic.

The fixed timing pointer has a straight edge and pointer. Which is the datum side? My manual is an electronic one bought from Gaydon and some of the photographs are very hard to read.

Running on ordinary unleaded with Millers VSP plus (lead substitute, plus octane booster), the fuel will approximately be the same octane rating as old leaded four-star, so I would suppose that the timings stated in the manual would be about right? What do others have their timing set at?

Kevin

[sorbs]

There should be markings on the pulley, and to turn the engine just use the fan (assuming you still have the fixed fan ), no need to remove the plugs or anything, it should turn quite easily. Couldn't be simpler.

I think I used the straight edge as the datum and it's set at about 12 ish BTDC. Should be 8BTDC but seems happier at 12.

[kevinw]

I am obliged, as they say. I shall have to give the puley a scrub with some cleaner to see if there's any more marks on it, otherwise it;s a bit of geometry. I'd sort of assummed the straight edge was the datum point, but have made some awful c*ck-ups in that past by making assumptions!

Still have the orignal fan and I usually do use this as a lever to turn the engine for things like adjusting the points - but haivn broken a metal blade on an old Ford once, it's another of those things that I do with great caution.

Kevin

[sorbs]

The numbers should be stamped into the pulley but are probably covered with grime.

I initially set mine to 8BTDC and the car then started really easily from cold but was sluggish and didn't start so well once warm.

I put it back to 12 BTDC (where it had been set for years) much more power and instant hot starting, but a bit more churning needed from cold.....Just like before I tinkered with it........

Incidentally, don't assume that the gunge on the front of the timing cover is just accumulated grime. I was about to scrape mine off and then found a picture of the timing marks in the car handbook showing a pristine engine bay with gunge on the timing cover - it's there for sound deadening!

[Alan Chatterton]

Rather than using a timing strobe to set it up......... I use a more basic method.

The answer is, you want as much advance as possible...... without any pinking.

So, advance the ignition (using the vernier) say 2 clicks. Then try it, if it doesn't pink at lows revs under load, advance again.. keep going till it pinks.. then back it off to the previous setting.

Voila!!

My estate runs at about 8-10 ish. using this method then checking with a strobe.

[sorbs]

Bearing in mind that the timing cover, pulley and pointer were all slapped together in huge quantities in a factory, I wonder how accurately the timing marks reflect the exact position of the engine?

If it's not at the official setting but runs well I'd be tempted to leave it or as Alan says, advance it as much as you dare.

[kevinw]

Yes.... I think the old adage of if it ain't broke, don't fix it comes to mind! Many, many years ago, I did a graduate apprenticeship assembling things like satellites and underwater weapons (torpedos) and then went to work as a computer engineer for a good number of years working on really close precision stuff and as a consequence, I have this sort of assumption that infernal combustion engines can be set up in the same way!

Kevin

[sorbs]

It's worth putting the timing light on it just to satisfy your curiosity, it's a bit of fun, and you can also rev the engine to check that the ignition advances with increased speed.

There are lots of variables, it's worth tinkering. Mine is certainly much better with more advance. I only use normal unleaded with lead subsitute when I remember about it and I've never heard it pinking so perhaps there is more to come?

As long as the distributor is working OK and is the right one for the engine I'm not sure that a timing light offers any advantage over setting it up statically. Maybe some can correct me?

[Alec]

Hello Sorbs,

I'm going with the timing light method, and you actually made a good point for using one in that the total advance can be checked quite easily and that it occurs at the correct speed.

Certainly using a book setting is only a starting point and road testing as Alan describes is necessary for optimum timing. However when that is achieved, check it with a strobe and that reading is what you set it to in future. (Assuming using the same fuel and additive if any).

Incidentally I see no reason to doubt the accuracy of the damper marking, or the pointer assuming it hasn't been thumped at some point?

Alec

[David Withers]

Alan, it seems a lot of time and trouble to set the timing by advancing on the vernier a bit at a time and taking the car out for a 'pinking' test after each go, and then checking it with the strobe anyway. Perhaps I'm missing something (no comments please!).

My procedure is:
# Set the contact breaker gap
# Set the advance to the maker's mark with engine static
# Check/reset using a strobe, keeping idling speed low so as to avoid any vacuum advance
# Check that it doesn't pink under heavy load

The straight edge of the pointer is used, and the job is made much easier if a thin white line is drawn in the correct BTDC groove on the rim of the pulley and on the very edge of the pointer. I also have a white line on the TDC mark. I think I used a typist's Tippex (white-out) pen for these.

If done carefully, distributors without a vernier adjustment can be left lightly clamped and then turned as the engine is running so as to get the timing spot on with the strobe.

The only thing that should cause a need to change from the maker's marks is if modern fuels make the engine pink under load, or you have messed around with compression ratios and suchlike, in which case it could be necessary to reduce the advance slightly. (I'm wondering if setting to only just avoid pinking is enough, as a fill-up on a journey could be with slightly lower quality fuel, ref: Alec's comments about using same fuel/additive?)

My 2500S engine is fine with the original ignition timing, running on unleaded fuel with no additive, however 2000s and PIs may well need a slight retardation. Once the datum has been set the pinking check should be needed only once in a long while, just in case fuel qualities have reduced or there is a change in the engine, e.g., a build up of carbon in the combustion chamber.

My car was auto, now manual, and I've always turned the engine with a ring spanner on the alternator pulley, squeezing the drive belt runs together with the other hand, just below the alternator pulley, so that the belt doesn't slip. I find this works even with the spark plugs in, though easier with them out of course. If I slip past the point I should be stopping at, I go well back before trying again so as to remove any backlash error.