68......I am having the same problem, same motor in a 69 GTO. I checked the dwell last night, my pontiac manual said the dwell should be between 30-32 degrees. I got the dwell meter on it..it was set at 25 deg!!!

Keep in mind I just bought this car and this is the first time and I am kind going over things......so I adjusted the dwell, then adjusted the timing. I took it down the road and it detonated at about 4000 rpm! really bad!

So I backed off the timing....drove it again....the valves started floating at around 4500 rpm!

Then I advanced it in the middle from where I had it the first time...drove it...now it has just a slight detonatation at 5000 rpm!

So should I be happy with that? Or is that not good enough? Is that slight detonatation gonna hurt me?

thanks

Brent