Hood Vents

In my quest to improve the aerodynamics of this car, one of the major areas that I am trying to improve is the flow of air beneath the hood. I have already addressed this to a point by making my vented inspection lids, however I felt like this would only be a start to the remedy.

The later-model 280z and all of the ZX models had a pair of hood vents from the factory, so there was obviously a need. Furthermore, upon doing some research, it turns out that tests had actually been performed that appeared to show that not only were these vents helpful, but that they could be even more beneficial if moved further forward on the hood. I liked this idea because it restricted the parachute effect of the air hitting the firewall since it let air get out before it even got that far. I also felt that my vented inspection lids would complement this by relieving any additional air pressure building up that couldn't be eliminated with these hood vents.

I tested several positions on the hood for both aesthetics as well as moving the vents forward relative to the stock 280z vents. All tests were done with the outside edge of the vent being 3" from the edge of the hood and all length measurements were taken from the rear edge of the hood to the rearmost edge of the vent where it comes to a point. The vent on the Passenger side was consistently kept at 6" (my estimate for the stock position in the later models), and the Driver side vent was measured at 6", 9" 12", 15", and 18".

I wanted the end result to be a vent that was moved forward, yet still aesthetically pleasing and not goofy-looking. In my opinion the 18" was just too far forward and I felt the 15" gave a nice balance between the point of the hood bulge and the inspection cover. In my final install, they are 15" from the rear and moved 4" to the center from the outside edge of the hood (rather than the 3" of my test-fit).

Now that I had a position laid out, I made a template for the vents themselves to show the outer border, inner hole, and mounting holes. The same template can be used for both sides and don't worry about it being exact but make sure you leave some room for error on the inner hole. It's better to have to grind off metal to ensure a tight fit than to have a nasty curve because you cut off to much material on the first pass (even though there is a decent overlap on the vent).

Once you've done the appropriate prep work, the install is pretty quick and simple. I would highly encourage the covering of your engine bay with a towel or peice of cardboard to catch any metal shavings (just keep any eye on the sparks when grinding). I wouldn't necessarily recommend drawing the outside outline for the template as I did, but it was really windy the day I did this and I didn't want it to be blown off course (should have just used tape...). Once the template is transcribed onto the hood (do both sides before cutting to make sure you like it), I would encourage the drilling of the mounting holes while there is a lot of metal to support you pushing on the drill; test fit the holes before cutting the center area. Get out your angle grinder and cut/grind to perfection and intall with 4 10mm nuts. DO NOT OVERTIGHTEN these nuts, these are not bearing massive loads and they will break off easily if you crank down on them.