Because I am located in the cooler climate of the pacific north west, I haven't experienced any real cooling issues. Obviously these cars have a ton of cooling capacity but it has always irked me that the hood vents are so covered up and restricted. The factory hood vent for the 16-18 SS might appear 15" long and 4" wide but the vent insert cuts that down to only a couple inches in both directions.
Aerodynamically, the vents are fairly flush but all that air that goes through the radiator needs somewhere to go. Mostly, I imagine, it dumps down underneath the car past the headers. Great for header cooling but not so good for generating downforce. Plus causing the air to mostly stay in the engine bay(or at least have to fight past all the things in the engine bay) will increase the air pressure on the aft side of the radiator, restricting flow. Restricted flow through the radiator generally means less cooling and more drag. Both things I feel I could improve.
Initially, I had removed the vent inserts last year during a hot PNW track day(air temp around 95) as a precautionary measure. Over the winter I thought about adding a set of Racelouver's hood vents or something but never bit the bullet on a set since cooling has never been an issue for me.
Aero however is something I am playing with. I figured if I could make a little ramp or kick up in front of the existing vents, they could generate a small area of low pressure that could draw air out of the engine bay, decreasing the air pressure behind the radiator and thus decreasing the drag on the front of the car. Racelouvers has a ton of data on their website show this if anyone needs to sate their inner nerdiness.
So rather than just buy something, I decided to design and 3D print a little ramp that could clip onto the front of the vent. There happens to be a nice little hole at the front corner of the vent, and the curvature of the hood isn't soo much that I need to compensate for it.
I snapped a pic with a reference measurement and threw together a quick CAD design in Onshape. I designed the piece to be about an inch tall, with a nice smooth ramp and some cool looking reinforcing strakes on the front and on the underside to help direct airflow. The edges are just slots with a gap of 0.04", approximately the thickness of the hood. I added a nice chamfer along the leading edges and sent the design over to my 3D printer. I also utilized the little bolt hole in the corner as a locating pin.
The first test piece matched up pretty well, but I tweaked the dimensions and reprinted 2-3 times before everything fit perfectly.
I thought the blue actually matched nicely, but because this piece would be seeing some pretty high air temps, I printed the final version in PET-CF. This material is supposed to be heat resistant up to 205 degree Celsius or about 400 degree Fahrenheit!
I like the look but might still do something to hide the blue edge of the hood that got revealed when I removed the OEM insert. The ramps look cool though!! Hopefully they are functional too.