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-   -   FJ40 Over-heating... (http://www.risingsun4x4club.org/forum2/showthread.php?t=13646)

ToddyBear 07-28-2010 06:16 PM

FJ40 Over-heating...
I have a 71' FJ40 with a small block Chevy Conversion, mated to an SM420/Stock Vacuum Transfer. My last trip to the mountains, pulling a single axle trailer and a dirt bike, had me reaching temperatures over 230!

I have a stinger bumper set up, currently without my winch mounted, so no wind blockage there. I have a flex fan with extension, without fan clutch. I've stuffed foam in the top and sides of the radiator and removed the thermostat. It doesn't have a shroud.

I'm headin up to the mountains again this weekend, and could use some advice! Flush again? Shroud? Aluminum radiator? Electric fan(s)? High volume water pump?

I'm running 37s/411s


Todd Gordon

corsair23 07-28-2010 06:22 PM

I know little other than every thread I've ever read about cooling stresses the importance of having a fan shroud...And not just so you don't get caught in the fan and chopped to pieces :)

Have you checked the basics and done the basic PM like flushing the cooling system, new thermostat, radiator cap, etc.?

Not sure what a Chevy small block uses standard for a fan...Maybe have your existing radiator flow tested and cleaned out or replaced if it is in bad shape.

60wag 07-28-2010 07:28 PM

x2 on fan shroud. Much more air will move through the rad with a proper shroud in place.

Flow testing the radiator to be sure its not plugged could rule the rad as being weak.

ToddyBear 07-28-2010 08:00 PM

Okay - I'll go out and flush the radiator right now! I've done it recently, however I was confused at the lack of fluid that came out! I ran the engine as usual, and I finally gave up and ended up refilling less than a full gallon of coolant/water. Maybe the radiator is not flowing like you guys suggested!!!

Would a stock radiator shroud fit, since it's the original radiator rebuilt?


71' FJ40 350/SM420,SOA,PS,ShackleReverse,37Irocs(Radial)

RLMS 07-28-2010 08:45 PM

Get rid of the flex fans, old tech! And usually too small in Diameter. Get a shroud, oem style fan, if you can


ToddyBear 07-28-2010 10:10 PM

Flushed the radiator - will look for shroud next. Instead of flex, would you recommend going back to fan clutch, or electric?

Thanks again for all the help!


Air Randy 07-29-2010 10:03 AM

If your thermostat isn't functioning right it can also limit the amount you will be able to drain out of the bottom drain ****.

Over heating like this seems to be the single most common complaint associated with V8 conversions into FJ40's.

Proffitt's Cruiser's probably does more of these conversions than anyone else this side of the Mississippi. Jeremiah told me they always put in a 4 core aluminum radiator with high flow electric fans as the surface area of the stock FJ40 radiator is too small. Any additional load like over sized tires, driving in the mountains, pulling a trailer, etc and you are always borderline for over heating. We have a Proffitt's built rig with this setup in a 1969 FJ40 and it has an automatic tranny to boot. My problem is getting the motor up to the 190 degree operating temp with this setup.

Do it step by step though. Get a good high flow fan and shroud first. Flow test the radiator. I know they recommend going to a high flow water pump on some of the SBC conversions. If you go to IH8MUD and read through the tech section on V8 conversions they cover all of the options in great detail.

ToddyBear 07-31-2010 08:22 AM

Again - thanks for all the help! I'm on it!


nuclearlemon 07-31-2010 11:59 PM


Originally Posted by Air Randy (Post 156967)
they always put in a 4 core aluminum radiator with high flow electric fans as the surface area of the stock FJ40 radiator is too small. .

x2. i ran a cheapy aftermarket four core that fit in the stock cradle with a taurus 2spd fan (like ford taurus). only time i had overheating issues was when the water pump puked on me. on a snow run, i was doing a long slow hill climb so i put the fan to high and it got too cold

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