As my screename implies, I have a ZZ502 crate motor in my Jimmy. I have had cooling problems with it from day 1 of the motor install. With my old motor (ZZ4) I had a brand new 3 core radiator installed with a single Black Magic fan (2800 CFM) with absolutely no cooling problems, in fact the same engine and cooling system is currently now in my 88 K5 with no problems. It will keep the motor at 180 all day long in all ranges of ambient temps. This motor runs a 40/60 coolant/water mix. No oil cooler. I have a 4 core radiator with the same Black Magic fan on my 83 K20 with a 650HP race motor. It has a 160* thermostat and runs at or around the 160-180 mark with little to no trouble. I usually run straight water or 10% coolant with Water Wetter to prevent corrosion. No oil cooler. This keeps the motor happy 95% of the time. Now onto my Jimmy.. I have a 4 core radiator (brand new Modine) A 28k B&M tranny cooler not running through the radiator, and a small PS cooler. I have (2) two Black Magic Fans (total of 5600CFM) pulling air through the radiator. The motor will get way too hot, I never let it over 220 or so. But to keep it at 180-200 I have to run the fans all the time and let them run between rounds to cool it down to 180-200 to run the race. Things I have tried and have currently.. ~Tried an Edelbrock water pump and a stock pump. The stock pump seems to cool better. ~Different T-stats 180 then 160 now none at all. ~Different mixtures of coolant. Brands, types etc.. Works best on straight water with Water Wetter ~I have checked timing and carb tuning ~I have 1 7/8" primary headers with 3" collectors and a full 3" dual system with H-Pipe ~New 115A alternator with yellow top optima to ensure full fan voltage. Fans wired on relays for optimal voltage as well ~I do not have a heater core hooked up. ~Would an oil cooler help? edit: I have a recovery bottle on all these trucks Someone has got to have an idea on this problem. I can run it to race by cooling it down, but driving it on the street is nearly impossible. Plus, I like to drive it every now and then for fun... /forums/images/graemlins/wink.gif I guess I could get one of those BeCool radiator and fan combos designed for 1000HP but that bad boy is like $1150 bucks. /forums/images/graemlins/eek.gif I think I should be able to cool this beast with what I have, but apparently not. I'm open to suggestions, comments. Thanks in advance, John ps. sorry for the long post.