What size fan do you have? I had issues with the stock rad and fan. I initally put an Northern ali ran on there with my M20B28. Even with the and a 12" fan it was border line on hot days, I put a 16" on and it has been fine since.
It now sits at 75C until it gets hot to the point where the fan kicks in around 80C - doesn't move from there anymore.
Rad:
12" Fan
16" Fan
EDIT:
The rad is branded northern, I got off ebay:
Comes like this so you can put the connections where you need them: