The WSM on maximum ignition advance.

[Michiel]

A question about the ignition advance given under General Data of the Worshop Manual. I have doubts as always... I have a series 41148A distributor so I assume the figures in the middle column are applicable. Should I add the 6°fixed advance to these figures? For instance: at 4.400 r.p.m. it says
19°- 23° deg maximum, so should I adjust to 25°- 29° at the crank? Or is 'Maximum advance' just that, and is the 6°fixed advance included.

[Bill_qaz]

I would think the 6 degrees is for checking/ setting timing with strobe,the other figure is the maximum total advance of the distributor and whilst it could be checked, charges can only be made within the mechanics of the distributor not by timing adjustment, providing it is set correctly to 6 degrees @ 600 rpm

[Michiel]

I am using high revs to check the mechanical advance. So you say the 16-19 degree at 4,400 rpm are inclusive of 6 degrees fixed advance.

[svenedin]

In theory you could check this if you have a strobe with an advance capability. With these strobes you set the advance degrees on a dial and then when you pull the trigger on the strobe and shine the light, the timing mark appears at TDC. So for instance, you set the strobe advance dial to 6 degrees BTDC and the revs to 600 rpm and then the timing mark appears at TDC (rather than at 6 degrees).

All I do is set the base timing at 600 rpm and then get an assistant to press the accelerator and check the timing mark moves to a greater advance. I’ve never actually checked the maximum advance.


Stephen

[Bill_qaz]

I am using high revs to check the mechanical advance. So you say the 16-19 degree at 4,400 rpm are inclusive of 6 degrees fixed advance.

Yes I believe so, so it's the initial advance plus the mechanical as the weights give max advance, the spring rate decide at what rpm this occurs. Without a tacho strobe you can also measure the circumference of the pulley and calculate/make your own 16 +19 degrees.mark.

[Michiel]

Bill, I did.

[Michiel]

Many thanks for your answer Bill.

[svenedin]

When I had my distributor rebuilt all of this was checked so I did not have to measure it myself.

This is the advance curve for my 41269. Distributor rpm is 1/2 engine rpm.

Stephen

IMG_8458.jpeg (2.13 MiB) Viewed 395 times

[Bill_qaz]

Many thanks for your answer Bill.

I have done similar in past but not on the morris, what advance did you get, did it match the wsm data? From memory springs used to be colour coded to change advance curve.
Very different from watching it on a screen and playing with engine management on a keypad as things are now.

[Bill_qaz]

duplication removed

[oliver90owner]

Read the attachment. The note below it states clearly it is measured crankshaft advance, not extra crankshaft degrees.

[Michiel]

I have done similar in past but not on the morris, what advance did you get, did it match the wsm data? From memory springs used to be colour coded to change advance curve.
Very different from watching it on a screen and playing with engine management on a keypad as things are now.

I really enjoy this kind of work. I cannot measure at the moment but will post the outcome.

[Bill_qaz]

Read the attachment. The note below it states clearly it is measured crankshaft advance, not extra crankshaft degrees.

What do you mean?
The crankshaft shaft degrees are the measure as in 6 degrees before tdc.

[Michiel]

Read the attachment. The note below it states clearly it is measured crankshaft advance, not extra crankshaft degrees.

Not so 100 % obvious to me . Note vacuum advance and "automatic" advance are stated seperatly. But thanks Oliver.

[philthehill]

The BMC distributer data above is really academic in that the data is for a 'A' series engine using a fuel (petrol) that is no longer available.
All that the chart will tell you :- is the advance both mechanical and vacuum advance working within the parameters of the data - yes or no.
You can set the ignition timing static as per the data/manual and then road test and adjust if necessary. Invariably you will end up setting the ignition timing so as to give best performance and which in all probability ends up having different readings/settings to the BMC data.

[Michiel]

I would like to see an thorough comparison of 1960s fuel and e10 translated into our WSM figures. So for our cars, what should for example 23 degrees at 4,400 rpm advance with 1960s fuel be with e10. RON, MON, additives etcetera.

[Bill_qaz]

Interesting Stephens distributor ( not on wsm list posted) has far less advance than the op model

[Michiel]

A professional rebuilder hopefully rebuilds a distributor in accordance with the series number's specification. But we will see what the cleaned and oiled 59.000 miles old distributor measurements show!

[svenedin]

Interesting Stephens distributor ( not on wsm list posted) has far less advance than the op model

Ah but I don't think there's that much difference. Multiply distributor degrees advance x2 to get crankshaft degrees.

Stephen

[Bill_qaz]

Interesting Stephens distributor ( not on wsm list posted) has far less advance than the op model

Ah but I don't think there's that much difference. Multiply distributor degrees advance x2 to get crankshaft degrees.

Stephen

True didn't read the sides of the graph