Maybe this doesn't qualify as it took less that 4 hours, but the Maine International road race I rode '77 as Cat 3. Rode the front, went off in a doomed break with 5 others. 30 miles after being caught worked my way back to within earshot of the front and was the last rider to make the split on the race's toughest climb. Threw my chain the next two hills. Still managed to stay with the lead group and finish in the sprint, 25th of 30 riders. (120 starters.) We all finished inside the old course record and 10 minutes ahead of the field. I was a complete basket case the next day and still wasted a day later.
The race was sponsored by a bank which sat at the finish. I crossed the line, went another block, got off, wandered back to the finish line, went into the open bank lobby, waited for couple of other riders to drink at the water fountain, took my drink and looked at the clock as I walked out. 4:00! I had looked at my watch just before the start and it was a few seconds before 12 noon. My watch and that clock were in sync! We covered 105.6 miles of hilly backcountry Maine. (On 20 pound steel bikes, toe clips, straps and not an aero anything in the peloton.)
That race was the hardest thing I have ever done. Now, it was a beautiful summer day and I"m guessing we had a light tailwind. (Not much though, I don't recall seeing a leaf move and I am a sailor. I notice things like that.)
Ben