Coroplast is plastic shaped just like common corrugated cardboard (as used on boxes). Coroplast is commonly used for campaign signs, spam signs, and scam signs. Take some road spam off of the road and you're doing the community a favor as well as getting free material, or ask a poltician after an election if you can have his old signs.

Ask:
A dealer parts and/or service manager.
Any Radiator shop.
Most any mechanic with initials on his shirt.
1-800-Radiator (ask the manufacturer)
The Vehicle Manual (the part titled: Capacities)

I've been experimenting with this recently. I have a 96 3.8L camaro. These cars have to front grill. all the air that goes into the radiator is scooped up from underneath the nose. I have a good 60 - 70% blocked with cardboard, and it is doing pretty well. I have to turn on my fans every once in a while in town, but it's due to get colder around here very soon. So i'll probably be able to block even more. Also my fans don't turn on till around 250 degrees, so i do it manually.

Is it normal in that car for them not to come on until 250, or is that a modification?

I thought the stock running temp for a GM vehicle was 195, with the fan coming on around 205.

250 IIRC is past the boiling point of even a 50/50 mix of coolant/water? 205 maybe...


Anyhow, I'd like to run a grille block myself, though I have no a/c parts to put the block between. I thought about maybe running a full grille block over the very front of the grille? It'd probably improve aerodynamics as well.

Yes, a full grille block in front of the grille will improve aerodynamics. A radiator block, up close to the radiator and allowing air to flow past the grille and into the engine compartment but not through the radiator, does not (in some cars it may do a little aero improvement). A popular compromise is a grille block directly behind the grille, still preventing air from entering but much less visible. Look for pictures of Jay's to see one example.

https://www.fuelly.com/attachments/fo...127046ac91.jpg

https://www.fuelly.com/attachments/fo...e03388c138.jpg

I'd have offset the holes to use more of the radiator.

Shatto: By all means, do what is best for you & your situation. What is pictured works for my vehicle in 100F heat in city traffic, without running the engine too hot, and still have the A/C perform reasonably well. Your personal combination of vehicle, climate, and types of driving you do may require something different.