FJ40 Radiator Size 350 Ram Jet

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May 25, 2013
Hi guys, I need a little help? Maybe a lot? I have a fj40 '71 that I haveinstalled a new ramjet chevy 350 in and I am concerned about the correct radiator size to make sure I protect my investment. The original shroud is for the original engine and is only 21" wide by 19" high. Is a rad that size going to cool that engine? Or should I go bigger? If so, how much bigger. Does anyone have good picks of the set they used? I am not much for metal work so I would be willing to spend a bit of $ on a custom shroud if anyone knows where to get one if I need to go bigger.
Any suggestions on a good radiator manufacture that will work with chevy 350? Any help would be appreciated. Thanks Rand
Might depend a bit on where you are and what your climates like but my 40 runs fine on the stock radiator, its a 4 core dunno if they are all 4 core or some are 3, it runs a 19" mechanical clutch fan with a homemade shroud, it runs around 180F on the highway and will only get hot when my radiator starts getting blocked with mud, most of our trails down here involve a lot of mud :crybaby:, I'm just in the process of finishing off a 31"x19" alloy cross flow radiator in the back hooked up to the heater pipes as a booster to help cool it when the main rad in the front starts getting full of mud, so far other than a couple of leaky joints to re do it looks like its going to work ok :)

If your going to put a bigger radiator in go as big as you can get in there
Ron Davis part # 28193. It's 29" wide , outside of tank to outside of tank with a 19" tall core.

X2 - IMHO, you should be looking for fluid capacity and radiator surface area numbers similar to the GM radiators that that formerly serviced the TBI/TPI SBC engines. Custom radiator brackets and a custom shroud are not that difficult to fabricate.
Just installed a 19"x22" crossflow rad I got at the Portland, Or swap meet. 2 one inch cores, and it cools my mild/mid built 305 without problem even though I'm sure it's an "import". Built a custom support that mimics the stocker, and bent up an aluminum shroud for the 16" electric fan. It will run right on the thermostat (180) most of the time, even on 90 degree days. When in traffic, or sitting at a light, it will slowly climb to about 200 when the fan kicks on and brings it right down. You can go bigger, but the opening in the bib is only slightly larger, and you get into the headlights pretty quick.

Stock radiator professionally dipped and rodded out, high volume water pump, heavy duty GM pickup fan clutch, 190-degree thermostat, no problems keeping the carbed 350 in my Pig cool for three years now. Temps here top 100 occasionally in the summer. It's crawled the Kokopelli Trail, been up over 12,000 passes been to CA, AZ and back, daily driver stop and go and handled it all. Usually runs about a third up on the temp gauge...occasionally reaches half way or slightly above.
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Recored stock rad with high density 3 core. No problems since 1996 with 300ish Hp 350. If I lived in the desert, I'd want more, but the rad was only a couple years old then the F died.

At first it heated up on the trail idling along at 600 rpm, a slightly smaller pulley on the ter pump solved that. With the original water pump pulley, the temp would climb when working near idle... But drop @ 800 rpm +.
Thanks all, I am in Pa and not going to be mudding or much on trails. Mostly around town show car. So what I am hearing is that a 22"x 19" with an electric fan and maybe a shroud would be fine. No need to go bigger? Correct? Thank you all.

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