My temp gauge starts @ 100 and we heat soak the engine for alum rods, seems I can get the oil hot then back down the water temp with the water pump and fan back to 100 pretty quick but it tends to leave kinda rough with the water temp that low, I have tried to leave @ 120 and it works, just not as good as 140, this is all @ 200ft track, I am thinking the 300ft deal is gonna push it over the boiling point under load, I am kinda weak on this subject cause all my experience is with marine diesels using heat exchangers, We have the whole ocean to remove heat, this fan and air flow thing is kinda tough to figure, my first instinct is bigger is better but space is a factor, I have been using 200 degrees as a safe limit for water temp, I don't know what the real safe limit for a race engine is? I have seen 230 a few times but not under load, long return lane with traffic & started to push water out the cap, I have been following most of the E85 posts and have been fence sitting for a year cause of the high humidity here on the coast and the water problems I have had with E10 in all the small engine stuff we have on the farm, seems I cant let anything sit for a week with E10 before it picks up water in the fuel, I am leaning toward fitting a 2 pass rad, any thought on this cause it will take a fair amount of fab work and i will have to lose the grill.