Jerkiness on overrun

[PaulS]

I have only recently got my 4L on the road here in France. I overhauled the ignition system fitting all new serviceable parts. I set the ignition timing statically and after minute adjustments to the distributor it pulls well. However I have noticed that on overrun as the revs drop, say when slowing down, there is a slight jerkiness through the drive. I do not think that it is the transmission. Has anyone else experienced this say, when the ignition timing is not correct. Any help would be great as this really impairs smooth driving.

 

[malcolm]

Ignition timing does cause that. From memory it happens when the timing is much too advanced. It is well worth buying a timing strobe light and setting the timing dynamicaly. Too much advance will overheat the valves on a run and it is easy to set too much advance by ear as the mixture tends to be weak.

 

[PaulS]

I am going to get hold of a strobe. In the meantime I made some small adjustments to the timing today and there is no difference.
Perhaps an air leak may cause this symptom...

 

[Niels Svane]

I had the exact same problem last february when I had overhauled the whole ignition setup, and serviced the carb. In the end I thought it had to be an air leak, but it turned out to be the ignition setting after all

I used a timing light to set the ignition dynamically, and it now runs like new. It takes a bit of fiddling to get the smoothest ride i found out

 

[PaulS]

Thanks. I am getting hold of a strobe early January next year. I'll post the results.