Kurt Busch posted the fastest average lap speed in practice at 168.445 mph, which is nearly 4 mph faster than the track qualifying record of 164.444 mph set in 2014 by Brad Keselowski.

This is the Cup series’ first visit to Dover (Del.) International Speedway with this year’s new aero package, which includes increased downforce.

Read Also: Kurt Busch tops blistering first NASCAR Cup practice at Dover

“It is really fast. Probably, I don’t know, probably too fast for here. The faster we tend to go in the middle of the corner doesn’t always produce the best racing,” Kyle Busch said. “We will see how that translates.

“It is going to be big numbers in qualifying obviously. But we will see how that translates into the race. I am not overly excited about it. We will just have to fight through it and see what happens.”

Busch said during practice qualifying laps he was never fully off his throttle.

“Lot of on-throttle time. You are never all the way off of it,” he said. “The IndyCar guys were flying around here, and they don’t come here anymore, because it was too fast, too dangerous for them.

“Eventually, there comes a point where it becomes too fast for a stock car, too. Whether that is or not, I guess that is people other than myself to think.”

Asked if speeds at Dover were approaching “the danger zone,” Busch said: “No question.”

"Pretty wild ride" - Truex

Speeds during Friday’s qualifying session are likely to be even higher, with NASCAR moving to single-car qualifying this week, which at Dover will include the faster of two laps. And teams typically don’t fully trim their cars out for single-car runs until the qualifying session.

“I can’t explain to you how fast it feels, it’s pretty hairy out there. Pretty wild ride, a lot of fun, but you really have to attack and we went faster every time we hit the race track without really doing a whole lot to our car,” driver Martin Truex Jr. said.

“Just trying to figure out where the limit is because it’s something we just haven’t done here before like this. Typically, I’m at my best when the track slows down and gets rubbered in, so this is pretty extreme situation of a day for me trying to get ready to qualify.”

Johnson nervous about the on-track product

Nine-time race winner Jimmie Johnson said he was less concerned about the speeds from a safety standpoint but more so in regards to how Sunday’s race will play out.

“As far as the type of racing we’ll see on Sunday, I am nervous about that. The faster we go, the harder it is to pass and the wider the race track needs to be,” he said.

“The critical areas around this track are pretty narrow. And there’s really one groove around the bottom most years I’ve been here. So, the tall spoiler, the higher speeds, I think that’s going to make the cars very difficult to really pass the car in front of you.”