Here's old Burt Reynolds talking about the guy who played one of those redneck rapists in Deliverence. The name of the actor was Bill McKinney:

[on Bill McKinney, with whom he worked in the drama Deliverance (1972)]: "I thought the other guy, Bill McKinney, was a little bent. I used to get up at five in the morning and see him running nude through the golf course while the sprinklers watered the grass. A strange dude, he moved to L.A. after Deliverance (1972) and worked in a lot of pictures of Clint Eastwood. He always played sickos, but he played them well. With my dark sense of humor, I was kind of amused by him. But as we got closer to the rape scene, I caught him staring at Ned Beatty in an odd, unnerving way. Ned would see it, and look away." - from the book My Life, published by Hyperion.

[on the rape scene of Deliverance (1972)]: "The day before we shot the scene I noticed McKinney hovering beside Ned and sat down between them. I wanted him to see I was Ned's friend. No different than in the script. Then I asked him how he planned to handle the rape scene. McKinney turned out to be a pretty good guy who just took the method way too far. Staring straight at Ned, he whispered, 'I've always wanted to try that.Always have.' Ned shouted , 'John!Oh, John!'. In his brilliance, Boorman reassured Ned but also brought in several additional cameras, knowing Ned wasn't going to give him a second, third or fourth take. Ned was only going to do the brutal scene once. When it came down to shooting it, Cowboy and McKinney were hands-down brilliant. Scared the shit out of everybody who saw the movie. People crawled out of the theater. None of that creepy 'Squeal, piggy, piggy' stuff was in the script. But McKinney, I swear to God, really wanted to hump Ned. And I think he was going to. He had it up and he was going to bang him. It's the first and only time I have ever seen camera operators turn their heads away. Finally, I couldn't stand it anymore. I ran into the scene, dove on McKinney, and pulled him off. Boorman, hot on my tracks, helped hold him down. Ned, who was crying from both rage and fear, found a big stick and started beating him on the head. Half a dozen guys grabbed Ned and pulled him away. We separated the two of them and let things cool off."- from the book My Life, published by Hyperion.