Ignition Timing - 12 1/2 before T.D.C.? Or differently with modern fuels?

[SpqrEddie]

Hello!
CLB engine were designed in the 50ies when 72 octane pool petrol was avilable. And timed at 12 1/2 degrees before T.D.C.
CLB after 2457, were already advanced to 21.
now that the minimum standard is 95 Octanes, should the timing be altered? what is is the reccomanded practice?
Should as well engine prior 2457 being timed to 21 degrees?
Thanks!!

[Big col]

In all honesty I don't know the relative numbers. The way I do it now is the way I learnt from my Daimler days.
It is important that both timing and carburettor tuning are done together or knowing that one is correct before setting the other.  Run the engine up to temperature, set the RPM to around 2500/3000. Loosen the distributor clamp and turn the distributor body too and fro to reach the highest rev rate then clamp the body up tight. Job done.

[SpqrEddie]

Hello!
anybody would know what should i see with a strobo lamp?

I can see three markings on the flywheel: a "5", a bar "I", and a "1 I 6"

With the strobo lamp i can see the "I" with the motor running very slow.

At what should i aim?

Thanks! and sorry the manual is not very helpful on this!

Eddie

[Big col]

Hello Eddie,

Again I am no expert, but I don't think you check the ignition timing on the flywheel.
I think it is on the front pulley, the one that drives the water pump.
There should be a mark for Top dead centre and one for (I think 10 degrees before) top dead centre.

Make sure number one cylinder is at Top dead by removing the sparkplug. Then wind the engine backwards to the 10 degree mark.(or guess it). Then use a light or multi meter to set the distributor till the light just goes out. Lock it up then run the car to get warm.

With a strob light you should see the mark on the pulley move anti-clockwise as you rev up the engine. It should move round relatively to the engine speed. More revs the more the mark will move.

Colin

[Big col]

Eddie,

One more thing, make sure that when the piston is at top dead centre on number one, that the valve are rocking on number one and not compressed.
Also make sure that the rotor arm in the distributor is in line with number one plug lead.

Colin

[SpqrEddie]

Hello Colin,
thank you!
i will try your method.

I tought i had to look at the flywheel as the manual says.

Thanks!
Edmondo

[B.P.Bird]

Flywheels carry various marks depending on period and model, but they all seem to have a 1|6 mark which is Number One and Number Six at TDC. Transferring these marks to the crankshaft damper with a white correction marker is a convenient ploy. I have often wondered how accurate these flywheel marks are, but they are certainly accurate enough to give you a starting point. You can use a large protractor to give you, say, a 12° BTDC datum for ignition timing on the crankshaft damper. Personally I just mark 10° and 20° BTDC and then you can see what is happening with the distributor advance and retard as RPM changes.
To be absolutely correct you need a pointer fixed close to the damper periphery so that you can take a reading,
Barrie

[Big col]

The main thing, which you don't tell us ,Eddie, is are you trying to start the engine or is it already running.
If it is already running then I still think the first post I mentioned is the best way to get it running well.
If it doesn't work then you have problems elsewhere.
If it isn't running yet and you want to get it running then take on board what Barrie and I say. If this doesn't work then you have problems elsewhere, because either of the methods will get even a reasonable motor running.

[Flyinghorse]

Reference the original question , is there not muddling up static timing ( ie 12.5 deg tdc) and centrifugal advance at full rpm. I assume the distributor used on the Weller 6 cylinder has centrifugal advance or a manual advance lever some where.
FH

[AEX 31]

Hello everybody,

In the context of ignition I have a question. I had the engine in AEX31 rebuilt some years ago with some modifications being made. Mainly higher compression and a fast road cam. Now I'm wondering if anybody on the forum have any experience with a slightly tuned engine in regards to ignition timing.

The company that helped me with the rebuild states that the static advance should be set to 2 degrees BTDC and full advance 36 degrees. If I then look in the data supplied by the AC factory they state 12,5 degrees for a standard UMB engine and 21 degrees for the later engines with a higher compression ratio. The enormous difference makes me wonder what other people's experiences are with this. To complicate matters even further Archibald writes in his 2-litre saloon book that an engine with a higher compression ratio should have an ideal static timing advance of 10 degrees... and full advance should be no more than 42 degrees on a tuned engine.

Obviously the advance curve of the distributor makes a big difference, as far as I can see from measuring a couple of standard Lucas DX6 distributors the full advance they gave was something like 12-14 distributor degrees which would equate to 24-28 degrees advance, on top of the static advance given as either 12,5 or 21.

So wonderful if anybody with experience of running a higher compression Weller engine could tell me and the forum something about their experiences in regards to what settings they use and how well that has worked, or not!

Thanks in advance for any input.

Regards Jonas

[SpqrEddie]

Hello!
sorry i forgot to report also on this thread on my findings.
https://www.acownersclub.co.uk/forum/index.php?topic=463.15

I have measured the distance between "I" and "1 I 6", the mark "I" is 1 1/4 before the mark "1 I 6", so i can confirm that the mark "I" is the firing point as per manual.

I did the timing with a strobo light, and it was completely off!

i did it with the static method, and now it is fine.

I will leave it like this, and alter during carb tuning in case of need.

Thanks!