Hopefully someone with a little distributor repair background can weigh in on this.
A little background - I put a rebuilt NAPA distributor in my GTX several years ago because of worn bushings in the non-original one in it. Typical of most rebuilt stuff I think it was assembled from bins of parts with no attempt to maintain original specs and it had about 30 degrees mechanical advance so it ran poorly. I finally got around to welding up the advance slots and filing them out and ended up with 20 degrees (crankshaft) centrifugal timing. From trial and error I discovered I had to be real careful to file the slots for a snug fit of the advance plate pins in order to maintain steady timing. Everything ended up running fine - big improvement with 16 degrees initial advance.
Today I was checking points and timing and points checked out at 28 degrees dwell which was where I last set them. I plugged the vacuum tube and checked initial timing and it was OK at 16 degrees - but I glanced back at the dwell meter and it was now showing 30 degrees dwell (??). I plugged the vacuum line back up to the distributor and the dwell dropped back to 28 degrees again. I repeated this several time with the same result. Otherwise the dwell reads steady and doesn't vary with reving the engine. So anyone have an idea what is going on to cause this? Doesn't seem to be hurting anything as it's steady under either condition.
A little background - I put a rebuilt NAPA distributor in my GTX several years ago because of worn bushings in the non-original one in it. Typical of most rebuilt stuff I think it was assembled from bins of parts with no attempt to maintain original specs and it had about 30 degrees mechanical advance so it ran poorly. I finally got around to welding up the advance slots and filing them out and ended up with 20 degrees (crankshaft) centrifugal timing. From trial and error I discovered I had to be real careful to file the slots for a snug fit of the advance plate pins in order to maintain steady timing. Everything ended up running fine - big improvement with 16 degrees initial advance.
Today I was checking points and timing and points checked out at 28 degrees dwell which was where I last set them. I plugged the vacuum tube and checked initial timing and it was OK at 16 degrees - but I glanced back at the dwell meter and it was now showing 30 degrees dwell (??). I plugged the vacuum line back up to the distributor and the dwell dropped back to 28 degrees again. I repeated this several time with the same result. Otherwise the dwell reads steady and doesn't vary with reving the engine. So anyone have an idea what is going on to cause this? Doesn't seem to be hurting anything as it's steady under either condition.
