“This heatsink seems effective at allowing overclocking.
However the one of the fans became very noisy within a couple of weeks. A bit of lubricating oil helps but does not fully solve the noise issue.”
“This heatsink case works very well on my Pi 4B. It keeps the 3 chips temperature to around 10 or so degrees above ambient room temperature. The highest CPU temperature seen was 56 degrees centigrade. The ambient at the time was mid 30's. The CPU was working hard at the time, but not flat out.
The fans are silent in operation and seem to do a good job.
There are a few of minor negatives... Power for the fans is from the main I/O pins which makes it difficult to connect to nearby pins. A HAT wouldn't fit directly on top and there are no screw holes on the fan side of the heat sink to mount anything above the heat sink.
To sum up. I am very pleased with the performance of the heat sink and I will be rerouting the fan supply wires and soldering under the the board to the 5 volt supply.”
