Pack Like a Boy Scout
A good track-day kit can save you a lot of time and frustration at the track. The bare minimum items are pictured here and include a jack, jackstands, air tank, tire pressure gauges, ½-inch cordless impact gun and spare battery, torque wrench, flashlight, battery jumper, drill, and basic tool set.
Your car isn't the only thing that will be put to the test at the track. Driver error is the number one cause of accidents and it's often due to fatigue. There's a certain buzz and excitement that comes with a track or autocross event that tends to remove the idea of eating and drinking from your mind. Proper hydration should start the night before and needs to continue through the event day. Pack high-protein snacks, water, and drinks like Gatorade to keep your energy up. A hydrated and fueled person is less likely to make mistakes behind the wheel.
Road racing is hot. Unlike drag racing and even autocrossing to some extent, road racing needs extreme focus on keeping things cool. Every car has an engine coolant temperature gauge from the factory, but oil temperature is even more important. The first thing to do is install a temperature gauge, and more than likely the information on the gauge will prompt the addition of an oil cooler. Plumbing is easy and could save your engine.
To keep the coolant temperature under control, you need a quality radiator, properly fitting shroud, high-flow fan, and a radiator cap that works. Every pound increase in the cooling system lowers engine temperatures but can also spring leaks. A 7psi cap may work great on street, but a well-built cooling system can support 24 psi of pressure. These caps need to be checked occasionally because they do fail just like thermostats. Many racers use a restrictor plate that fits in the thermostat location and limits the water flow through the thermostat housing. The idea is to remove the potential failure of a thermostat while keeping water from over circulating.
Race cars are not allowed to use traditional coolant because if it leaks onto the track, it can be a major hazard and is difficult to clean up. Coolant is very slippery, but distilled water with additives like Water Wetter is not. They don't have the corrosion protection that coolant does, but race car engines aren't left unopened for very long so that's not as much of a concern as on a street car. Non-competitive track days and autocross events won't have a no-coolant requirement.
Rollbars are great for safety and performance. The flex in a car's chassis changes so much about how the car handles. You may see something as small as a strut tower brace to help keep things square, but every race car will have something. A full rollcage like the one pictured will give maximum rigidity, but for a street car it's pretty intrusive. Kevin welds the seams on the front-end sheetmetal and incorporates this custom plate to remove flex at the base of the tower. These are things that don't have any downsides, which makes them great for street cars too.