Scuncio Chevelle ex-L78

[TomN]

On to the next issue - seems that there are a lot of little issues when trying to get a car back on the road in workable condition.
The mechanic (fixing the pinion seal) noticed that my right rear brake drum was dragging a little. You could hear that there was a high spot on the brake drum by the rubbing sound when turning the axle. So I had the brake drum turned by a friend who has a muffler and brake shop. The brake drum was a little out of round - so that has now been fixed.
OK - I took this car to the Pure Stock Drag Races in Michigan this past Sept. Later in the day the car slowed down. After making several runs between 13.90 - 14.10 .... the car suddenly ran 14.30. I went right back and made another pass and went 14.60. So I knew something was wrong - but what. My guess was maybe ignition, so I put in a different distributor. Car did improve to 14.20 - but that was the best it would do the rest of the weekend.
Now I'm wondering if it was the brake shoes rubbing - holding the car back.
I don't think the "self-adjusters" should over adjust the brakes - but could the out of round brake drum have caused an issue, where the brakes over tightened.
The car doesn't miss-fire. O2 sensor in the exhaust doesn't show the car to be running out of gas. Yet the car slowed down.
Any thoughts .......?