Harvick's #29 Chevrolet and Hamlin's #11 Toyota made contact on the track as the second practice session of the weekend kicked off at Dover, both ending up with bodywork damage on their cars and driving into the garage immediately.
Once they pulled into their adjacent garages both had a face-to-face outburst, with members of both teams also getting involved until NASCAR officials headed by Sprint Cup Series director John Darby intervened on the scene.
Both Hamlin and Harvick lost plenty of practice time while their cars were repaired, the former's apparently getting the most damage as both the right front and right rear of his Toyota were hit by the RCR's Chevy.
On Friday, Clint Bowyer made a spirited defense of his outfit's case after being penalised for irregularities found on the car he drove to victory at Loudon last week but also raised doubts about the legality of Hamlin's and Jimmie Johnson's cars from Loudon.
Later on the same day, Hamlin, who finished second at Loudon, hit out at Bowyer and dismissed his arguments - claiming that his rival's cars had been suspected to be illegal for a long time already.
"This is something that's been going on for months," claimed Hamlin on Friday. "They've been warned for a long time, way before Richmond. This is not something that, 'Oh man, they just told us halfway after Richmond and going into Loudon that our car's wrong.' They knew it was wrong way before that and I felt like they just, they wanted to get everything they could."
Bowyer's team boss Richard Childress hit back at Hamlin following Saturday's clash with Harvick and suggested the Chase leader should back off from the attack on his outfit and the team's general manager Mike Dillon, who was part of the exchange with Hamlin in the garage.
"You're not going to win a p*****g contest with a skunk, and you don't throw rocks if you live in a glass house," said Childress. "I wouldn't even think of going after Mike Dillon because I can tell you what, you're getting a bull if you go after him.
"We're all a good, tight-knit group. We're here to win races. That's all we're here for."
No penalties are expected for either the drivers or team personnel involved, according to NASCAR officials.
The appeal hearing for RCR and Bowyer's penalties from Loudon has been scheduled for next Wednesday.
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