Underhood aero...worth it?

[J-440]

Evening all. I have a 68 Dodge Charger which is not the most aerodynamic car in the world but I'm improving it otherwise. Am looking to get more airflow from under the hood and I wanna run this by ya'll. I already have a glass 3 1/2" cowl hood with heat extractors from a '14 Mustang that work well. What I'm looking to do is fab a thin sheet of aluminum covering the huge gap (looking down at the car with the hood open) from the edge of the grill to the radiator. It's about a 5 1/2" gap in the middle then tapers on both sides to about an 1" towards each fender.
By covering this "V" what aero gains would I see? Or would this be total overkill for an 80% street car? I also like the look of overhead fender louvers like you see on newer Vipers and Porsches to get the air out of the wheelwell. Thanks again.

[astroracer]

No way of determining what "gains" you would see without a few wind tunnel tests. I doubt you would see any at all at speeds below 70 miles an hour. You MAY improve cooling though by forcing all of that turbulent air to go THRU the radiator rather then around or over it.
Mark

[expensivehobby22]

Not sure of the exact style of extractor/louver setup you mention but venting underhood air is typically a good thing. These old cars have LOTS of aero front lift and anything you can do to reduce it will help things. I'm not saying that it will be night and day from a handling perspective under normal use, but it is directionally correct for the most part. The original Challenger that we put in the tunnel as a benchmark when we started development on the modern Challenger looked like it was going to take off at highway speeds. Ideally, the louvers need to be in the correct position on the hood as well to take advantage of the area of low pressure and generate the strongest effect, ie 08 vs 03 Viper louver placement. That's the main reason why we moved them forward for the 08 hood.

[J-440]

Yeah I've read about the hood extractor placement. Mine are placed a tad rearward from center. This was done as to not cut into the reinforcement ribs in the glass hood. Guess I'll find out how much lift I have when the time comes.
As far as the cooling goes, my car sits at 200 idling in traffic during a Texas July. Now, let's say I'm on a road course, anyone guess what the degree difference would be with that sheet metal installed over that gap I mentioned?