With nearly three decades of racing and championships behind the pair, its hard to think of something that could bring out a child-like emotion in two men.

Don't ever underestimate the power of simple.

Granted, stepping into a machine for the first time is hardly for the novice, but the idea of swapping cars brought out the inner child of Lewis Hamilton and Tony Stewart on a damp day northern New York.

"I guarantee you it's going to take a couple days for all of what just happened in a short amount of time to sink in," said Stewart, who completed a first in his decorated career thanks to another such accomplished racer.

The Columbus, Indiana native-who has won titles at the IndyCar and NASCAR Sprint Cup levels-swapped rides with Hamilton-the 2008 F1 champion-at Watkins Glen International on Monday.

Stewart took laps in Hamilton's Vodafone McLaren Mercedes Formula One car while Hamilton took out the Mobile 1 Chevrolet stock car.

"Like when I used to go go-karting, used to have so much fun," said Hamilton of driving Stewart's  Whilst driving a Formula One car is fun, the competitive side of it's so serious. I was  feeling the tough weekend this morning. 

"But as the excitement built up, when I got in the car, once I got out, I completely forgot about last weekend."

Each driver had four laps on the 3.4 mile road course at Watkins Glen, each doing what the could to get a feel of the machine. Stewart, in fact, spent time in a simulator trying to get a feel for the F1 machine before stepping in, but nothing compared to the real thing.

"The funny part is I couldn't even get it up high enough in the revs to get it to pull away in first gear.  It goes into a default stall mode," said Stewart.  I was trying to tell myself, Just get on the gas a little bit. Once we got rolling, it was unbelievable. The good thing is you have somebody like Lewis that can sit there and guide you through it."

In the same capacity was Stewart, who helped Lewis get the feel of the stock car, something which he'd not driven in his life. But he like his stock car counterpart was able to get around the track problem free.

"I was really, really surprised.  I was thinking this could be rolling quite a lot.  I didn't know how stiff it was going to be," said Hamilton of the stock car. "I tell you what, it handles really well.  It's absolutely fantastic. 

"The shifting and the engine, the way it's pulling through the rpm was fantastic." 

While not the same machine, Stewart also added that his knowledge of downforce from IndyCar helped him to acclimate to the F1 machine as he went along. Still the McLaren Mercedes gave him a feel of the track to which he has yet to find in his long racing career.

"It's just amazing what the capabilities of the car are," said Stewart. "I told the guys on pit road out there that it's probably going to make my crew chief a little more stressed during the weekends because I'm going to want it to handle like that all the time."