Hey, I put a koyorad in my 2008 z. Because of the thicker radiator, and the free-floating nature of the radiator mounting, there is very little clearance between the overflow tank and one of the sprockets on the engine.
After a track day, I found that there was contact and a bit of the overflow tank was grinded off.

Is there a easy solution to this. Are there thinner overflow tanks? Or maybe I can secure the radiator closer to the core support with some zip ties or something. It seems like this would be a common issue.

Thanks

 

Which specific Koyorad did you get? These are typically designed for a factory fit, meaning you shouldn't have any problems with clearance of items like the fans, fanshroud, or coolant overflow. I don't have an HR Z, but I put a Koyorad in my 06 and the only clearance issue I had was with the lower condenser brackets hitting the core support. I had to make some minor relief cuts for a clean fit. Otherwise, no issue. The thickness of the endcaps is the same as OEM and the veins don't exceed the size of the endcaps.
-Icer

 

So I found out that the overflow tank is quite different between the HR and DE. The hr has another intake where the DE overflow tank , so it mounts the overflow tank behind the fan.
I also found out that there are suppose to be rubber bushings on the top of the radiator, which makes sense in hindsight. I guess at one point someone removed the readiator and forgot to put them back on my car. I ordered a set and I'll try that and see if it fixes it.

 

Yes, precisely why I asked which P/N Koyorad, because there's an HR specific unit and a DE specific unit. They're easy to spot because the radiator cap location is completely different as well. Regarding the radiator mount bushings, on the DE version, there should be two rubber mounts/bushings at the bottom and the top is secured with plastic twist locks. I "think" the HR version follows the same design.
Cheers!
-Icer