2007 Civic Lower Grille Block
 

So after a seeing Vman455's grille blocks and general ecomodding awesomeness I felt inspired to progress my grille block. I had the upper grille and hood-to-grille space blocked off with duct-tape covered styrofoam and that has held up fine for a couple years now. So I used some of that foam similar to the pool noodle stuff but this came in a sheet form initially intended for an in-window air conditioner. It's about 1/2" thick. I cut out the shape and wrapped it in some duct tape and then black electrical tape. It's just wedged into the grille - no fasteners. See pictures below for the results.

http://i.imgur.com/Lfa2Q00.jpg
http://i.imgur.com/tvJPcfz.jpg
http://i.imgur.com/vM4LrMG.jpg
Before Block
http://i.imgur.com/lrd9xqv.jpg
After Block

There's a 6" x 2" gap left below the license plate. Any comments on if that should be enough airflow to prevent overheating? Temps right now are in the low 30s to high 40s - but with high humidity. Seems the car never warmed up all the way until about 5 miles into a drive.

That looks good, I like it. Based purely on the amount of grill you have open, I think you have airflow still, as long as there is part of the radiator near the open section of the grill.

I've blocked my lower grille completely with tape and had no problem. Gained about 1MPG on the hwy as well!