Originally Posted by Granpa

They generally tech the top 3 in each heat. The cars are impounded right after the race so theres no monkey business, no pun intended. The rpm limits seem to vary at different venues. At the Nationals a closely controlled handout motor system was used and rpm limits were set for some Regional races.

When rpm limits were used, the motors were tested on a Muchmore type motor tester. These testers test under no load conditions and provide rpm and amp draw numbers. Some call these testers dynos, but a true dyno uses a load of some type.