Poor idle and off-idle performance after distributor swap

smokinnjokin said

I made a mark on the distributor for reference before taking it out to swap cans, afterward I put it in the exact same spot and it was like 10 degrees off. Weird that just swapping vac cans would drastically change the orientation of the distributor.

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Of course they will. There is no guarantee that a vacuum advance is going to be exactly the same as another. The way the vacuum changes timing is the rotation of the breaker plate. So if the arm is a tiny bit off from the original it will change the timing.

Remember dist. degrees are half crank degrees. So if you only change something in the dist. makes a difference of 5 degrees, it will change 10 degrees at the crank.

Don't you have a timing light?