Slant heat riser block off/delete?

Decades ago, the heat riser in my 1969 Dart was rusted stuck and the flapper gone. I knocked it out and put a bolt in each hole with a captive nut on the inside of each (nut w/ washer face w/ teeth to bite in), I recall stainless steel. They were still there years later when I had to take off the exhaust manifold again. That was in Atlanta and don't remember any cold weather start issues or overheating when driving.