Hello again RX8club. I ended up replacing my radiator as part of my RX8 rebuild/restore so I wanted to share with you all the re foaming I did on my brand new radiator. I bought this Denso2219238 radiator from Rockauto for $107.79 plus shipping. This was a bargain compared to Mazda's price of $400+ for what appears to be the same part minus the foam. To address that, I picked up some foam from ACE Hardware which closely matched the size of foam still on my factory radiator. This foam was 2 1/4 inches by 2 1/4 inches square and had enough to do the full length and the bottom with some left over I might use on the oil cooler openings. I used an outdoor and HEAT rated liquid nails product which goes on like caulk and dries clear but is very strong. I only had one spot come loose that I'll re-glue. I will take some more pictures once I get the undertray remounted, but here are the pictures. I was really happy with the results and it also sealed the opening the fans had at the edges of the radiator core on both sides.



I cut a slit in the side of the foam for the AC line


All installed minus the wire harness clips

 

Thanks for this. Going to attempt it this week, and the previous owner of my car replaced the radiator and it looks like the foam is missing which explains my car's sub-optimal cooling.