It will depend on your build and how the air-management is handled.
I have only a single puller fan behind the radiator...as long as it is cool, I don't even need the fan unless I am in extended stop 'n' go driving, but in the hot weather I worry that overheating might be an issue (I have seen a water temperature of 220*, but only b/c I forgot that I had turned the fan off).
Shrouding to keep all the air that goes through the fishmouth opening going through the radiator, too, will help a lot. Mine does well without shrouding on the sides, only shrouding to keep the incoming air from flowing over the top of the radiator.
The only time I ever get "edgy" regarding coolant temp is when I've been sitting in Houston rush-hour traffic for half an hour, outdoor temps are above 100*, and the black asphalt of that 6 lane freeway is sending up enough heat to fry eggs. I posted a thread suggesting that a waterpump-mounted fan might help move hot engine compartment air out more efficiently, but most of the replies convinced me that with some "Water-wetter" coolant additive I don't really have a problem.
We'll see this coming summer when I put it back on the road, I guess.
Cheers, and good luck with your build, from.....
Dugly
