IGNITION TIMING

ALAN COCHRANE · Post by **ALAN COCHRANE** » Mon Jun 17, 2013 5:24 pm

Hi Everyone

In an effort to stop my S1 1962 OTS from pinking , I have been checking the timing with a view to retarding the ignition.
The first problem I discovered was that initially there appeared to be no timing marks on the crankshaft balance wheel.
I rotated the engine around to the point where the rotor arm was facing No6 igniton lead. I checked the balance wheel and a red mark on it was very close to the pointer. Rotating the wheel until the red mark was exactly in line with the pointer corresponded to the points being open with the lever right on the crown of the cam lobe in the distributor. So far so good.
When I used my strobe gun on the wheel it showed that the engine was set to approximately 18 degrees before TDC. Has anyone else come across a setting this far in advance?
It may be the original red mark was not accurate, which I will check.
using the spark plug and clear tube in the jar of oil method I've seen on the old Interweb

As always all advice gratefully received.

Cheers

Alan

vrracing · Post by **vrracing** » Mon Jun 17, 2013 6:55 pm

I'd never heard of the oil/tube technique. Found this write-up on two variations.

http://tinyurl.com/k9xtd4l

Thanks!

Jim

ALAN COCHRANE · Post by **ALAN COCHRANE** » Mon Jun 17, 2013 7:43 pm

Jim

That is the method I was proposing to use except for the oil in the cylinder bit. You can put one end of the tube in a jar of light oil. On the compression stroke the tube will blow bubbles in to the oil. At TDC this will stop and once you are on the power stroke oil will start to be sucked up the tube.
Alternatively you can put a loop in the tube with oil in the bottom of it. This time the compression stroke will push the oil up one side of the loop and stop at TDC. Then the oil will be sucked back down on the power stroke.
Both these methods have the advantage of removing the need to clean out the cylinder when you're finished.

Alan

christopher storey · Post by **christopher storey** » Tue Jun 18, 2013 9:04 am

Alan : I fear that the blowing bubbles method is hopelessly inaccurate for these purposes, because at the very top of the stroke there is virtually no piston movement but quite a few degrees of crank movement. The crank pully usually has markings at 4 degree intervals on it, so a good wire brushing might pay dividends . The correct setting is 10 degs BTDC for the moment at which the points begin to open, best determined with a bulb, or voltmeter, in series with the distributor feed wire. If your pulley/damper does not have the markings except for TDC, you can fairly easily reconstruct them using 3.142 X Diameter to get the circumference, and dividing by 90 to get 4 degree intervals around the circumference. If you are still having trouble determining TDC , it is best found by eg a wooden stick at a slight angle down the plug hole ( to avoid the dome) and averaging i.e. taking the mid-point between the point at which the stick stops rising, and the point at which it starts to fall again. Finally, with your strobe ensure that you have disconnected the vacuum advance before doing a check

ALAN COCHRANE · Post by **ALAN COCHRANE** » Tue Jun 18, 2013 3:17 pm

Chris

I realise there is a "flat spot" at the top of the piston travel but I am only using this as a double check against the red mark I have found on the balance wheel. Hopefully they will correspond. The points lever is right on the crown of the distributor cam lobe so I'm fairly sure the red mark on the balance wheel is correct. The timing may well be this far in advance, but I just want to be sure.
Can anyone tell me how much advance/retard you can achieve using the Vernier adjustment on the distributor. The manual only mentions 6 clicks which isn't the most helpful. It's a Lucas DBZ6.

Alan

PeterCrespin · Post by **PeterCrespin** » Wed Jun 19, 2013 10:42 am

Your issue was pinking and therefore in the face of a well-running engine with this 'malfunction' you can somewhat ignore timing marks and specs designed in the era of 100 Octane leaded fuel.

Just mark where the distributor is now and back it off fractionally until the pinking stops. Bring it forward a touch so it reappears (as a check) and then fix it permanently at the no-pinking point. Empirically-speaking, the theoretical degree figure is irrelevant; what matters is the setting at which your engine no longer pinks with your distributor springs and your level of tune and carbon build up. The rest is academic unless the engine is sick.

Pete

Vegard · Post by **Vegard** » Wed Jun 19, 2013 10:57 am

Great reply.
However, when that is said, pinking could also come from engine leaning out or most likely a combination of these.
Do you know if it gets the amount of fuel it deserves? :)

JEP41 · Post by **JEP41** » Wed Jun 19, 2013 1:06 pm

I agree with Pete on this one, having just had my lightweight copy on Peter Baldwin's rolling road in Wimpole, Cambs. Peter's way of setting the ignition timing was for me to set the engine at 5000rpm in 4th gear on the rolling road he then proceeded to slacken off the distributor and adjust the timing while watching peak power on the rolling road readout. From my original setting which gave 321bhp Peter achieved 330 bhp by advancing the distributor until the power started to drop off. He then locked up the distributor at this point and we did two further power runs to check for pinking but none evident. This also shows that with my engine making peak power at 5000 rpm, revving any higher is probably a waste of time :o
Note! Peter Baldwin is a master at setting up classic cars, running with carbs and conventional distributor setups. He still races a Mini Cooper S despite being well past the government retirement age.

Vegard · Post by **Vegard** » Wed Jun 19, 2013 1:17 pm

As a matter of fat, I've visited Peter twice, and I concur. He is a master at setting up SUs and Webers. He also know his way around Brands Hatch ;)

ALAN COCHRANE · Post by **ALAN COCHRANE** » Wed Jun 19, 2013 3:29 pm

I seem to have set off a bit of a debate with this one.
I have balanced the carbs and the mixture is set correctly according to my Gunson Colourtune. This was confirmed when I removed the spark plugs and they were a lovely light brown colour.
The car runs very well apart from the pinking issue. I intend to retard the ignition to resolve this, but it'd be nice to know what the engine was set up at to start with. I'll let you know how I get on.

Cheers

Alan

ALAN COCHRANE · Post by **ALAN COCHRANE** » Wed Jun 19, 2013 7:59 pm

Latest update. I checked the TDC with the tube and oil trick and the red mark I initially found was indeed correct. For some reason my timing had been set to approximately 18 degrees BTDC- no wonder I had pinking!
I retarded the ignition by 4 degrees and went out on a test run. The pinking had almost disappeared, with only a slight trace with the throttle wide open. I retarded the ignition a further 2 degrees and on the second test drive the pinking had completely disappeared. So by my calculations the timing is now sitting at 12 degrees BTDC-much closer to the 10 degrees recommended in the manual.
I'm going to check the mixture and carb balance again at the weekend and hopefully that'll be it-apart from the seeping rear carb float chamber-next on the list to do.
Thanks everyone for the advice.

Cheers

Alan

PeterCrespin · Post by **PeterCrespin** » Wed Jun 19, 2013 10:01 pm

Vegard wrote:As a matter of fat, I've visited Peter twice, and I concur. He is a master at setting up SUs and Webers. He also know his way around Brands Hatch ;)

Did you have the bonnet up so the fan struggled to blow onto the rad core? Angus took his VSE there (I used to go nearby on my daily commute) and it wiped out #6 piston from revving the nuts off while he tweaked the dizzy...

I thought it was probably due to poor cooling with the bonnet up at high loads/revs and the dyno fan not in a good position. Wasn't there so I don't know, but angus was a little crestfallen after taking up my recommendation to go to him. Never used him myself. Never used anyone, come to that.

Pete

Post by **1954Etype** » Wed Jun 19, 2013 10:22 pm

Thanks for reminding me Pete. Yes, number 6 partially seized while starting the dizzy swing. I think it was due to the bonnet being open resulting in the external fan not doing a great deal. I should have worked it out at the time bug didn't. Still, you live and learn!

christopher storey · Post by **christopher storey** » Thu Jun 20, 2013 10:28 am

Alan : you seem to have misunderstood my original post. If when your marks are aligned the cam lobe has the points fully open, then you are way past the firing point. The point at which the spark occurs is the instant the points start to open . It is at that microsecond that the primary winding voltage collapses, and the HT voltage is induced in the secondary winding of the coil

PeterCrespin · Post by **PeterCrespin** » Thu Jun 20, 2013 11:58 am

I read it that Alan was regarding the red dot as TDC on the firing stroke Chris? That corresponds with points wide open, although it's not a specific setting of course. He was using other means for determining true TDC. The double-stop method is most accurate on an assembled engine as you hinted, but if the car no longer pinks with good fuel mixture and performance, he's probably 95% home and dry.

Pete

ALAN COCHRANE · Post by **ALAN COCHRANE** » Thu Jun 20, 2013 12:00 pm

Chris

No I didn't misunderstand your original post. I was looking for TDC not 10 degrees BTDC which as you rightly said is where the timing should normally be set. But I wanted to find out where mine was actually set before I started adjusting things. It might seem a bit pedantic but my engineering training is deeply ingrained-always confirm the conditions at the start and go from there!
I discovered a red mark at what appeared to be TDC and using the tube in the jar trick I was able to confirm this with reasonable accuracy.
I was then just a case of retarding the ignition, in this case a whooping 6 degrees, to make the pinking disappear. The fact I had to retard the ignition so far lends more weight to the initial setting of 18 degrees BTDC being correct.
I suspect the car has pinked since I first got it but being unfamiliar with the symptoms combined with very infrequent use, means I can't be certain.

Alan

JEP41 · Post by **JEP41** » Thu Jun 20, 2013 12:42 pm

Hi All,

With reference to Peter Baldwin's rolling road doing a power run with the bonnet up. I watched the temperature closely on all the power runs, having experienced over heating with a Kawasaki on Straight Line Racing's rolling road in Kings Lynn several years ago. The temperature on my E-type which utilises an alloy rad with Pacet fan barely went above 78 deg C during the power runs.

Vegard · Post by **Vegard** » Fri Jun 21, 2013 9:09 am

PeterCrespin wrote:
Vegard wrote:As a matter of fat, I've visited Peter twice, and I concur. He is a master at setting up SUs and Webers. He also know his way around Brands Hatch ;)
Did you have the bonnet up so the fan struggled to blow onto the rad core? Angus took his VSE there (I used to go nearby on my daily commute) and it wiped out #6 piston from revving the nuts off while he tweaked the dizzy...

I thought it was probably due to poor cooling with the bonnet up at high loads/revs and the dyno fan not in a good position. Wasn't there so I don't know, but angus was a little crestfallen after taking up my recommendation to go to him. Never used him myself. Never used anyone, come to that.

Pete

I've only been there with Minis. Not posh stuff 8)

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