2011 21.5” iMac 27” three tube mod (fairly easy)

[Supermac05]

Super new to iMac modding(started 12/30/2025), but I figured I’d post this here since I haven’t seen any photos of this. (still in progress) I ended up installing a three tube gpu cooler from a 27” model, and besides the optical drive being removed, plus the stand internal protective plate being removed for clearance, the first three radiator fins being trimmed on the new cooler to accommodate the standard cooler mounting arm, and the two small sections milled away to fit my 770m on the heat sink, everything seems like oem fitment! I’m temporarily using a small section of an old charger to slightly limit the up and down movement of stand since I would hit the heatsink otherwise. As of right now, I’ve got a 1tb ssd to replace the hdd, 32gb ram for maximum flexing during the shortage , a Xeon 1260L cpu, and a RTX 770m installed, and I’m working on printing/modeling efficient airflow pathways to accommodate for some of the removed stock ducting. Currently with all the components installed, and screen seats with zero interference, or points of contact. (Also, let me know if this isn’t the right place to post this…im new here, and definitely haven’t hit the learning curve yet…)

 

[Supermac05]

All done! Overall not as much of a headache as I would have expected. I had to flash the gpu with a poor man’s hacking tool since it wasn’t the right bios, but other than that, everything went in smoothly. Still working on ducting, but the prototype is keeping the temps down so far. I did notice with the bigger gpu cooler that the top right of the screen doesn’t seat completely (screws still bottom out) but when the glass is installed, you don’t see it. If anyone is interested, I can share more photos of the internals, and the fitment of the 27” iMac three tube cooler in my 21.5” iMac.