Almost ready to give up on this intermittent detonation issue. once I think it is solved it returns!!
New primary spring in which was thicker than the old fatigued one.
static to about 9/10 degrees. All ok but engine was not heated up fully.
Looked promising but was I wrong.
Was in heavy traffic last night and accelerating fast hearing pinging above 3000 rpm again!!!!!
Got home, lowered it back to 8. Was a bit sluggish off acceleration.
couldn't test it fast again due to the traffic.
This is proving to be tricky.
I hope is not the secondary spring that needs replacing.
I believe its the sum of both of them that control the advance at higher revs.
So if I put a thicker primary spring in then it should lower the total advance.
New wideband sO2 sensor coming my way so I can get my afr kit set up again to see fuel mixtures.
Maybe its going lean at 3-4000 rpm, but it doesn't feel like it. Just sounds like it.