I just went through a bunch of distributor tuning myself. One thing I did not check was the rotor phasing. However, I do use the vacuum advance which will move the phasing around a bit.
The VCF408 (Advance Auto's #) vacuum advance can be adjusted down to zero. I currently have mine set at about 8 degrees. I have used this same can in the Duraspark distributor, but the arm has to be bent to fit.
About that viton sleeve on the mechanical advance stop post. A missing sleeve caused me greif years ago. The symptom came through as a sputter at the rpm where the mechanical just start to touch the post. Over about a 200 rpm span the mechanical would bounce off the post unill there was enough centrifugal force to keep the plate pegged against the post. The timing was jumping up and down about 20 degrees. I thnk that's all of what was available in the range slot.
To fix, I used some heat shrink tubing on the post. To narrow up a wide range, just do more layers of heat shrink.
A few weeks ago I was fooling around with the heat shrink tubing on the stop post and couldn't get the range where I wanted it. So I came up with a better idea. Being I only use the light spring for the advance and bend the post for the heavy spring to where it won't make contact, I decided to modify the heavy spring to act as the mechanical limit and not worry about the stop post. What I used was a link of that small chain used to hang a flourecent lamps. I was originally thinking of a piece of bailing wire, but you'd have to twist it in a knot for it to hold. The lamp chain wire diameter was a little smaller than a cheap wire coat hanger and was right for the task. So, I took one link and put it through the spring then bent the ends over to limit any stretch of the spring. I suppose there is just enough stretch in the hook areas of the spring to cushion any bouncing of the mechanical as it reaches the limit.
I knew I was going to post this online at some point. I should have gone home to get the camera.
Another benefit of using the restricted spring is that you can simply bend the spring post through the little square hole in the breaker plate to adjust the timing range. When working with the original stop post I would have to remove the breaker plate everytime.
I will modify another distributor this week and take a picture of the spring that I put the chain link on.
Yes, please post your pictures, I would like to see them. Sounds like an interesting idea.
