But why in the world would you wanna to race with your hood just popped but not up. It will affect your areodynamics. It will cool down the engine much better but it wont help you go faster or anything..
Vented/scooped hoods are the way to go, also a upgraded front bumper with extra vents will help much too.
BTW, sure pop the hood but with the saftey hooked up and also even with your custom pin or saftey bracket or etc, go 100 mph and see how your hood likes that kind of stress. Im not trying to sound like a smart ass or be rude but, your hood wont be able to handle that kind of stress, Imagine drivning in a big field and a huge powerful gust blows directly in front of you and that will break the hood bracket right off the car! Even with the custom saftey pin or bracket or whatsover that is holding the front hook, will be strong enough to hold the hood and you will be still at the speed and the hood is gonna be flapping all over the place like crazy hell fish that got itself unhooked and fell on the very extreme hot surface of the aluminum fishing boat's vee hull!
So.. do you get my point? or are you talking about, while at the track how to cool down the car?