Even a small amount of forced airflow, rolling at 5mph or having the fan on, will disrupt convection, it's relatively weak, which is why chimneys need to be tall to get good draft in still air. (They get a lot more in a slight breeze too)

Definitely a good mod, IMO. However, I believe you will find that those particular ones are fakers and will need to have holes cut in them to be actual vents.

To all those wondering why, this would redirect some of the air coming in through the grille up and over the car, instead of underneath it. That means cleaner aero and more stable at speed. Google pics of the Ford GT-40. They used a complete duct so all grille air went over the car. No need for grille block then, but it is not always easy to put such ducting in a production car.

Thank you, BluEyes. I left the Gt 40 out when mentioning the Lotus Elise and Exige in my thread. The Ford GT-40 has a better example of radiator out flow top slots in my view.
Richochet, 14/06/08

my car has hood vents right on top of the engine. hot air rises, so that's the best position for the vents in order to dissipate heat.

hood scoops are different. as the name implies, they scoop air into the engine compartment while you're driving and are not for venting heat (although they will vent heat when your idling). hood scoops are best placed near the engine's air intake to maximize cold air for power. these are mostly at the sides of the hood or at the front of the hood and the air will be "scooped" into the engine compartment and cool the area right where the intake is located. in general, hood scoops are placed where the air intake is located in order to scoop cold air into the intake.

while driving, hood scoops will create more drag, an actual hood vent (you see these types of hoods with holes behind a "bump" and has no scoops above the holes) would actually use the vaccum created by the airflow over the bumps to vaccum out heat.

I leave my hood vents open in the summer and block them during the winter.

I know this sounds odd, but if you want hot air to rise up and out, why not put them on backwards? Thus avoiding some of the aero drag. Air goes in at radiator, through engine compartment and up and out the vents.

I think that's a good idea. the scoops in turn become hood vents.

:thumbup: good plan make sure you get real vents

https://www.240sx.org/links/installs/hood/hood12.jpg
I think I go will this kind of hood vent. It will the the cheapest hood vent to make and the most effective. Check this out ...https://www.240sx.org/links/installs/hood/hood.htm

that works :thumbup:

You could also put some spacers where your hood attaches to your car. This will raise your hood near the windshield and allow some of the hot air to escape. I've seen drifters use this technique because of the extra heat from their turbos.
It's real cheap (just cost of spacers) and easy to do (& easily reversable if you don't like it).