Got a bit of a detonation problem on the new engine and I think it might be down to the ignition advance. Basically what I think is happening is the new cam runs more advance on idle than the old one did. This means the total advance when the revs are high is too much and that's causing the detonation. On the run up to the nats I backed it off by about 5 degrees and it's much better, not perfect but now it suffers a bit off idle, stumbles a bit which I don't like. I tried a tank of super unleaded but it didn't make any difference so it can't be the fuel and the plugs look fine so I don't think it's running lean at the top end. So I'm going to be altering the mechanical advance on my distributor. What I think I need to do is shave a bit of meat off these weights so they don't fly out as far: Anyone done this before? I have a pair of spare weights... Or those two bits that the springs hook into, I think I remember they were slotted. Is it a matter of shortening the slot with a thin weld and a bit of filing so it doesn't open as far?