This past weekend the officials at the local track decided to tear down a few cars in the sportsman class. (358ci max, 2bbl carb, prod heads, pump gas, open cam & valvetrain) In the past, the have always just pump tested the motor with a tool that threads into the spark plug hole and has a floating piston to show the mass of air being moved while the engine was cranking.
This time, they surprised everyone with a new toy that I had never seen before. This tester was a blue box that had to be plugged into wall current, and required a high pressure air source (they used a CO2 bottle). Like the pump test, the device was threaded into a plug hole and they asked that the engine was manually turned until the compression stroke began for that cylinder (intake valve closed) The device had two hoses that ran to the "cigar shaped" spark plug fitting. To perform the test, they entered the temperature of the head into the machine, and it clicked and bled off some pressure and told them the engine was legal. Unfortunately, they wouldn't share the results, or tell us how close we were to being illegal.
Common sense tells me that they were measuring the volume of the combustion space, but does anyone know what this device is called and exactly how it works?
What would stop someone from running a cam with a later IVC number to hide some extra cubes?