Grill blocking - vertical or horizontal
 

When blocking grill openings is it better, or does it matter, if I block the lower openings in my bumper and leave the main grill open or if I block some of both from the outside working my way in?
In my case it’s a 66 Chevelle so here’s a front pic.
I was going to block the two extra openings on either side of the licence plate. The area between the bumper top and grill bottom does have a filler panel in there it’s just black so you can’t see it.
Does it matter or am I over analyzing this?
Thanks

My guess would be whichever gives the most direct path to the radiator itself. That suggests closing off the sides.

Rather than a flat plate, a curved panel that bellmouths the radiator's opening would improve air flow if there's any way.

I don't think it matters too much, I'm sure we could debate or calculate air flow for whatever given dimensions....

The only thing I'll mention is to keep in mind that any blocking being done will inherently raise the pressure at the front of the blocking and/or reduce the pressure directly behind the blocking. Which will increase the flow through the remaining areas (radiator).

Thanks. I’ll continue with my plan to block the bumper openings first. If I don’t experience any cooling issues with that, I’ll start to close in the grill area slightly from the outer edges towards the center.
I should be able to roll the edges some to give it a gentler flow to the radiator too

where?
 

* If you had the space, your inlet would be low, as wide as the radiator core, with the height equal to 1/6th the radiator core height, feeding an airtight, diverging duct in between.
The 1956 LOTUS Eleven built for Le Mans remains the standard today.
https://www.google.com/search?q=1957...0zMsPD-SLWPs_M
Without the space, you might just limit the opening to directly in front of the radiator/ AC condenser, and only as large as the actual heat exchanger core area.

The grill opening aligns with the middle part of the radiator. Roughly the middle 3rd. The upper portion is covered by the leading edge of the hood and the bottom portion is behind the bumper.
You can see in the pic below that there is quite a bit of grill opening on either side of the radiator core. I can block that and roll the block back to the core support.
You can also see that about half the bumper opening align with radiator. As an alternative I could just block the outer portions of these openings.

outer portions
 

Right!
Some of the members have done all this blocking 'behind' the grille, thereby preserving the original aesthetic of the car. Blacked- out, or done in Plex / Lexan.
The extraneous outer portions of the bumper penetrations, same-same.

All of my blocking will be from behind too. The air dam is about as much deviation from stock as i want.