I was adjusting the timing on my 3.0l yesterday and noticed that the mark jumped around about two degrees. It was erratic, no real pattern to it. I was wondering how steady is other peoples marks when they have do this.

 

mine does that i dont know why but it always has and seems to run fine, i run mine at 17* with afm cog clicked one degree rich "to help prevent detonation" and premium fuel. im getting about 300 miles a tank so around 20.

 

It runs fine, I was hearing some detention every now and then so I checked the timing and found in at 15*. I cut it back to 10* and the detention is gone, imagine that. Power is about the same, no noticable difference. I was wondering if the mark jumping was caused by distributor noise, worn bushing?

 

Mine jumps around a bit too when jumpered. It is usually not so bad that I can't establish a base line to set my timing. I run mine at 12* and use 87 with no detonation.

 

This is usually, but not always, caused by distributor issues.