What’s a Pop-Off Valve — and Why You Need to Know for the Daytona 500

Note added 14:14 2/22/12:  OK, I did predict that this was likely to change.  You can look at the chart on the video and see that the temperature at 28 psi is about 271 F.

One thing you will hear a lot as soon as coverage of practice starts Wednesday will be speculation about possible changes to the pop-off valve on the radiator.  What is a pop-off valve and how will it affect the Daytona 500?  Here’s the answer:

One of the reasons for the focus on the pop-off valve is that it’s one of the most easily adjustable pieces of the strategy to prevent tandem drafting.  If the temperatures are warmer, NASCAR can raise the pop-off valve pressure if they think there might be a need for more cooling.  EFI makes changing restrictor plate sizes a bigger deal than it used to be – so if there are changes, this (and the size of the grill opening) are the most likely places for them to happen.


  1. Hi Diandra. It looks like NASCAR might need to revisit your tutorials. It appears some serious overheating issues need to be addressed before Sunday’s race. The pop-off valves were increased to 28 p.s.i. for today’s Gatorade Duels. Cars were getting overheated after 10 laps, whether they were hooked up or not.

  2. Speaking of pressure relief valves, NASCAR has long needed to let teams use bleed off valves on their tires, as have been used in other racing series for decades.

    This would allow them to start off with optimal tire pressure, and maintain it, instead of having to start with ridiculously low tire pressure to compensate for pressure build up in the tire due to heat.

    I know they could overcome any technical difficulties if they are worried about an air bleed off valve being knocked off by contact with another car more easily than just a regular tire stem.

    There you have a new topic started! Heh.

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