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Discussion Starter #1
I just installed a 304 in my CJ7. It runs great, but gets really hot after about 20 minutes of driving it. This has happened everytime I take it out. I had a pinhole in the cap of my radiator that I have already fixed with a new cap. But, it still is overheating now, not quite as bad, but still running way too hot. I am not sure if there is something wrong with the radiator or what? Is there anyone out there that runs an aftermarket radiator with their 304 and could give me some advice on it?

My other thought is that my fan is too small? It is only a 15" fan. Will that cause the overheating issue? If so, what kind of fan should I get? THanks for the help.
 

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Dopey
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im guesing you had a 258 in there before? if so a bigger radiator, 3 core. i tried the 2 core when i swaped to a 360 and couldnt keep it cool. try a lower thermostat. is it a mechanical or electric fan? do you have a shroud?

i run a 3 core w/ a 160 thermo stat and a electric pusher prolly around 15" never measured it. i run about 165-170 driving in city traffic w/ the fan on and about 185-190 on the highway.
 

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what temp is it running.
and running a lower temp therm. can make it worse.
if your sitting at 190 with a 165 therm its becouse the therm is never closing and the water in never sitting in the rad. getting cooled down, its always cycling and never cooling down.
 

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Dopey
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how would running at 190 be bad?

and it must be cooling down if it stabalizes at 190 otherwise it would keep climbing
 

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how would running at 190 be bad?

and it must be cooling down if it stabalizes at 190 otherwise it would keep climbing
its not bad. its what it should be. but he most likely wont get the same results.
the fact that it is stable at 190 is only bad in that it should be at 165 with your thrm.
if the system was working rite you would be stable at 165.
if you take it off road and drive slow in 4 low and need to use the skinny pedal you most likely wont be stable at 190 eather.
i went thru this a couple of years ago in one of my cjs, rite down to the 165.
it would sit at about 200 driving normaly but when wheeling it would over heat badly
went back to a 190 therm with a three core and ele. fan and the prob. stopped. the coolant was given enuf time in the rad. to reg. temp prop.
 

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Playing Possum
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Are you running a fan shroud? They don't cool worth a crap with the engine mounted fan and no shroud. The fan should fit the shroud and be positioned correctly also. Either that or go with an electric one that has it's own shroud.
 

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Not Right!
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Are you running a fan shroud? They don't cool worth a crap with the engine mounted fan and no shroud. The fan should fit the shroud and be positioned correctly also. Either that or go with an electric one that has it's own shroud.
x2

I had a BB ford in an old f250, new motor and rad. No shroud, ran hot as hell even in cooler weather, add a shroud it got better, but once I spaced the fan out and made sure it was running just inside the shroud it would run 190-195 no matter what the outside temp or how I was driving.
 

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MTU 4x4
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what temp are you running? I consistantly run 210 with my 304, in 100 degrees or -30. I run a Ford Taurus fan, and that helps out a good deal. The AMC motors tend to run hot, at least mine always has
 

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I am the law.
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A clean 3-core radiator, the stock thermostat, and a properly functioning water pump is all you need for a 304 in a CJ. They were fine like that from the factory, so yours should be fine as well. You don't need all these damn electric fans or to play musical freaking thermostats to cool a factory-offered powertrain configuration. If its not cooling, you don't have a sufficient radiator (left the I-6 2-core in as mentioned), or your cooling system is inefficient (restricted on the inside, dirty on the outside, losing pressure someplace else, etc). Get a pressure tester or have the test done to see if there is another leak.

The shroud is a nice thing to have and will move more air over the motor, but not a requirement. A bigger fan is also nice, but its not really a matter of diameter. You want one with more blades. Get a 7-blade thermal clutch from a FSJ. I happen to have an extra one. PM me if you are interested.
 

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F-U-CANCER!!!
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my 2 cents

How are you checking the temp.?
If it is the factory gage, you may want to try an aftermarket to verify.

What is your timming set at?
The higher it is set, the more heat you will make.

I will have to disagree with PP on a couple things (no :stan: intended).
1. The shroud is important to have. Will move more air through the radiator, and past the motor.
2. The blade will move air dependant upon all 3 things listed bellow.
A = Diameter
B = Pitch of blades
C = # of blades


Notes about how I am fighting heat:

I am running a 3 blade FSJ blade and clutch on a 360
Stock (3-core I think) yj 4.2 radiator.
Not running the auto tranny throught the radiator (seperate cooler)
Added redline water wetter just for insurance (seems to drop 10-20 degrees).

This is working ok, I can not run alot of timing advance (about 1 degree past stock (11 degrees?)) like I would like to. I realise you are running a cj, but I thought my info. might help.

good luck
 

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I am the law.
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Fan shrouds were installed on an extremely small amount of V8 CJ's from the factory because its just not required to cool one. IIRC, they came on CJ's equipped with HD cooling for plowing, etc.

I highway DD'd a 78 on 33's with a cam'd 304/T-150, 3.73's, and fenderwell headers for a year that had a lot of advance and required premium to not ping. All it had was a 3-core radiator.

Straighten out your cooling system before you start putting band-aids on it. It doesn't matter how much water wetter you use, what t-stat you run, or whether you have a shroud if sufficient heat transfer is not taking place. Use the right type and capacity radiator for the job (or overbuy in this department), make sure you have circulation, keep everything clean, and try not to block the radiator with lights and crap if possible. :thumb:
 

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Discussion Starter #13
I am running a 190 thermostat with a radiator from my old six cylinder. I was told the radiator was a 3-core from the guy that helped me drop the motor in. It is identical to the radiator in his 304. I also did have a shroud on my radiator but took it off after the engine got hot for the second time. As for checking temperature, I have an aftermarket temp gauge that is run to a water port in the intake of the motor.

I think I am going to stop today and see if I can get a different fan. How far should the fan be from the radiator?

By the way, the temp would begin to rise from startup and not level off until about 235-240. I don't know if it was going to keep going, because I always shut it down at that point. I also don't think that there is anything plugged in the radiator, because when I start the engine up cold with the radiator cap off I can watch as the temp rises and the thermo opens up, the fluid just flows passed the cap very quickly. The problem is, is that I don't believe it ever stops circulating. I believe that is where my problem lies. Water pump is new, thermostat is new, not sure where to go now. Thanks.
 

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Resident HVAC/R Jambi
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You most deffinetaly need to see an ACURATE measure of tempurate before jumping to any crazy solutions. When I droped in my 304, and hooked up the CJ temp gauge, it read higher than my 258 read, but still runs at 190.
 

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Discussion Starter #16
I feel that my temp gauge is pretty accurate. The engine got up to almost 250 two days ago, and it was blowing radiator fluid out of the hose on top of the radiator. I have had this temp gauge in my CJ all summer with a six cylinder. It ran consistently around 160 all summer. What is the easiest way to check the temp of the fluid with something other than the temp gauge?
 

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Discussion Starter #20
Thanks to all who gave me some great info. I ended up taking the radiator out because it appeared to be plugged up. I had an extra 3-core sitting in the garage. I dropped that in and flushed the entire system. Did that yesterday morning and drove about 65 miles yesterday with no problems. Thanks again for the help.
 
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