Hey everyone,

I'm thinking about ways to improve the aero of my 70 Challenger. For those not familiar, the grille on that car is recessed and the hood extends a good distance over the recess, which means that air gets trapped in there and pushes up against the hood, causing it to rise at the front of the car. It's a little scary at 90+. I can see why so many people put in hood pins, but I've never liked that look and while they would secure the hood, they wouldn't do much to make it more aerodynamic.

My thought is to fabricate and install a new grille, one that is closer to the end of the hood, very much like the 69 Charger 500. I was wondering if anyone else had ever tried anything like this, or had any ideas. I love driving this car but for my sanity I keep it under 80, because I really don't like seeing the end of the hood vibrating up and down.

Any ideas? Thanks.

Get the car low. Run wide, speed rated tires. Stiffer t-bars and leafs with a very flat arch. High quality shocks. Run a front air dam and ducktail spoiler. Reduce pump pressure if you have power steering, run a big dia. steering wheel. For the grill I’d copy the Silver State Classic 68 Charger: https://www.hotrod.com/articles/45098-1968-dodge-charger/

By a new car and sell your Charger to someone who appreciates it.

Interesting, but a little extreme for a street car. I assume they had to modify airflow for cooling as that front seems to block off all or most airflow. But it does get rid of the air trap. Thanks.

I believe they were running 160+ mph. The original article went into more detail, lots of aircraft spec fasteners, etc. You’d have to direct air up through the lower valance to feed the radiator.

I'm thinking the air getting under the car at speeds is doing the lifting, not the hood.
That being said I would put a front spoiler on the car to help eliminate any air getting under it like the 1970 Dodge T/A Challenger had
I had one of those cars back in the day and I don't remember the front end getting light above 100 MPH

To clarify, it's not the front end getting light. The front end is fine as far as I can tell. It's just the far end of the hood vibrating up and down, presumably from the air getting pushed against the grille and then up against the edge of the hood. I'm used to the design of 71 B bodies where the hood edge is further in from the front of the car and isn't as affected by the airflow.

Thanks.

A 1973 Challenger without a front air dam will hold on until about 110-115. Then the front end starts getting light. Over 120 and it starts really fighting against the air. Or so I’ve been told.

I used to run my '72 Challenger in time trial events, totally agree with the above. I never worried about the hood wiggling at speed,
On the back stretch at Road Atlanta I was pushing 135mph, after I fabricated a simple plywood front spoiler. Don't laugh it really helped!
I had it bolted to some simple brackets and removed it when street driving. I just tried to copy the design used on the Sam Posey Challenger, though mine wasn't as low.
If you refuse to drill holes in your lower valence. I'd lower the front with shorter tires or torsion bar adjustment. and block off as much air as you can that comes through the grille.
At high speeds you won't need as large an opening as you'd think. You can install your blocking panels behind the grille if want to keep a more stock appearance.
I'd start by blocking everything behind the front bumper 'cause that won't show. Your idea to move the grille out is good, but I'd still block off as much as you can behind it.

If you are talking about a street car and you don't want to impacts the looks when you occasionally run up to triple digits, there is nothing you can do, unelss you are willing to sell your 70 and pick up a 72-74 with a more flush mounted grill already present.

If you are running track days where you don't mind a specific modification that can be reversed for the street, some sort of frame the fills the surround, can bolt to existing hardware, and has screen door screen stretched tightly over it can actually do a lot for pushing the built up pile of air around the nose instead of allow it all to go through. The mesh does allow enough airflow for the radiator, but acts similar to a small sink strainer when excess air is pushed against it.

There is a guy from SLC who races here occasionally with a small block 1970 Challenger that does over 150 thru the traps. He has a clear lexan shield across the grill opening with some small holes drilled in it to let a little air thru. Not sure if this would work on a street car without overheating issues?

I'll assume the hood latch & hood bumpers are adjusted for best fit & no up/down movement.
Either you limit the air in, or vent it out, usually through the hood. Look at GTLM & GTPro racecars for examples.
I recall a calculation from many years back: it stated that at speed (70+), the air intake opening needed to be only 1/6 the size of the radiator.
Obviously not great at trolling speeds, though.
The valance opening would be pretty effective with an air dam, as many cars (example: 80s-90s Camaros) have proven.
To accomplish the OP's goal, dead-stock appearance is pretty much out the window.

Get your fiberglass out...

One of my favorite cars!