The cars are held at the top of a slope until race directors pull a lever, and gravity pulls the cars down the slope onto a stretch of flat track. The fastest one to the finish line wins.
Asked what all the excitement was about, Garrett shrugged and smiled.
"I don't know. ... It's a lot of fun," he said. His car would end up in 10th place at the end of Saturday's races.
Saturday's races were among the top contenders from pack-level races in January. Both Adler Garrett and his brother, Zane Garrett, 7, made it to the races Saturday, said their father, Brennan Garrett.
Brennan Garrett said it took about two weeks to put the cars together - "with a lot of help from Dad." The pack races were in late January.
He said he was surprised by the crowd. There easily were 200 children and parents in the audience, cheering on their sons' and grandsons' creations.
"We didn't think it was going to be this big," Brennan Garrett said. "They seem to be having a really good time."
Kerri Melby, 36, of Williamsport, was watching her son, J.P., 6, race.
"It's just a lot of fun," Melby said. "I think for the fathers more, or as much as for (the kids)."
Scott Paddack, district executive director of the Mason-Dixon Council, said the races Saturday were the fastest he had seen, even though there are few things that can be done to make them faster.
The standard lubricants - oil and grease - can't be used, so graphite is the standard. And for axles, the cars only may use nails, Paddack said.
Asked how he made his car go faster, Adler Garrett said he added some U.S.A. stickers, and "I just made mine shaped like an arrow. I put some weights on the side."
Lastly, Garrett said, "We just painted it red."