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Unread 12-23-2009, 07:53 PM   #1
Mudviper
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304 Normal operating temperature?

What is the normal operating temperature of a 304? I know it probably depends on what thermostat is installed, but when I let the CJ7 idle it runs normally around 160 to 180. When I start driving down the road it drops to around 140 and a little below. I have never had an engine run that cold before and this is my first CJ, all my others have been XJ's and YJ's and they stay pretty consistent at 190 to 200 even when driving around. It's had been around 25 to 40 degrees outside so that could be a reason why it is running so cold.

Thanks

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Unread 12-24-2009, 01:32 AM   #2
KMD
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Quote:
Originally Posted by Mudviper View Post
What is the normal operating temperature of a 304? I know it probably depends on what thermostat is installed, but when I let the CJ7 idle it runs normally around 160 to 180. When I start driving down the road it drops to around 140 and a little below. I have never had an engine run that cold before and this is my first CJ, all my others have been XJ's and YJ's and they stay pretty consistent at 190 to 200 even when driving around. It's had been around 25 to 40 degrees outside so that could be a reason why it is running so cold.

Thanks
That is where mine runs but I have a constant drive flex fan. The fan makes it run really cool which is good because it dosent take long for an AMC V8 to overheat. So you are fine. I plan on putting in an electric fan motor and shroud in the future.
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Unread 12-24-2009, 05:58 AM   #3
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I am running duel electric fans on it right now and they do not come on until the engine temp comes up to 180, so if I am running at 140 while driving around, the fans never come on..lol. It actually takes quite awhile for the engine to come up to 180 when idling
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Unread 12-24-2009, 06:38 AM   #4
jfwireless
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The thermostat determines the operating temp if all is well with the cooling system, so it sounds like you have a very low thermostat for your 304. I have a 180 degree thermostat in my 304 and it runs under 200 degrees all the time. It sounds to me like your thermostat is a little low, 140 is to cool for the 304 in my opinion. I have a junkyard TBI install on my 304 and it would not even go into closed loop at 140 degrees. I believe the default temperature for GM TBI closed operation is 160 degrees. As I recall the stock thermostat for the 1976 304 was 195 degrees with the engine always above 200 degrees.

No matter what type of cooling fan you have it is the thermostat that determines the operating temperature for the engine, assuming you have enough cooling capacity for the designed operating temperature.

Jim
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Unread 12-24-2009, 06:41 AM   #5
KMD
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Do you have a thermostat installed?
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Unread 12-24-2009, 08:20 AM   #6
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Well this thread makes me fell better.

I just got my 304 running and with the electric fan on (sounds like a jet taking off), the thing barely reaches 130 when driving. With the fan off, it was about 160 when driving - but i'm DEATHLY afraid that my temp gauge is wrong and I'm afraid to leave the fan off in case I cook my motor.
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Unread 12-24-2009, 01:51 PM   #7
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Quote:
Originally Posted by jfwireless View Post
The thermostat determines the operating temp if all is well with the cooling system, so it sounds like you have a very low thermostat for your 304. I have a 180 degree thermostat in my 304 and it runs under 200 degrees all the time. It sounds to me like your thermostat is a little low, 140 is to cool for the 304 in my opinion. I have a junkyard TBI install on my 304 and it would not even go into closed loop at 140 degrees. I believe the default temperature for GM TBI closed operation is 160 degrees. As I recall the stock thermostat for the 1976 304 was 195 degrees with the engine always above 200 degrees.

No matter what type of cooling fan you have it is the thermostat that determines the operating temperature for the engine, assuming you have enough cooling capacity for the designed operating temperature.

Jim
How does that TBI conversion work for you? I have only had my CJ7 for about and month and took it out for the first time to do some hill climbing and it was getting a bit frustrating stalling all the time with the carb. Would like to do a fuel injection conversion on it.
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Unread 12-24-2009, 03:14 PM   #8
jfwireless
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The junkyard TBI 304 has never ran better. Getting around 18mpg, used to just make 10. It took some time but worked out just fine.

Quote:
just got my 304 running and with the electric fan on (sounds like a jet taking off), the thing barely reaches 130 when driving. With the fan off, it was about 160 when driving - but i'm DEATHLY afraid that my temp gauge is wrong and I'm afraid to leave the fan off in case I cook my motor.
Get the proper thermometer and read the cooland temperature to compare to your temp gauge


Jim
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Unread 12-24-2009, 04:49 PM   #9
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Quote:
Originally Posted by jfwireless View Post
The junkyard TBI 304 has never ran better. Getting around 18mpg, used to just make 10. It took some time but worked out just fine.



Get the proper thermometer and read the cooland temperature to compare to your temp gauge


Jim
Definitely, just a matter of getting to it... Been really busy and will be to the weekend. Then i've got Sat/Sun to work on it all day. But i'll definitely check it.
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Unread 01-18-2010, 10:32 AM   #10
UncleBrad
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So the proper operating temp for the 304 is what?
(wife here, hubby asked me to sign on and find the answer to this question)
Just got this Jeep and it seems like there's been many mods made to it.
TIA
Terri
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Unread 01-18-2010, 10:37 AM   #11
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As said, it depends on the temp of the thermostat used.

With a 180 thermostat the temp should not drop below 180

With a 195 the temp should not drop below 195.

If the thermostat is doing it's job it will open/close at the temp stamped on it. Temps can go higher than the stamped temp if the cooling system isn't doing its job, but they shouldn't go lower for any length of time.
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Unread 01-18-2010, 10:42 AM   #12
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Thanx CSP, I'll go out to 'Man Camp' and let him know.
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Unread 01-18-2010, 10:48 AM   #13
_Kyle_
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I just put a new thermostat in my CJ with the 304. Little did I know the one in it had a piece of wire jammed through it! NO WONDER it wouldn't get to temp or anything!! Not it runs around 195 all the time.
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Unread 01-18-2010, 11:40 AM   #14
jfwireless
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I have a 180 degree thermostat and my 304 never goes over 200 degrees. As i remember the stock thermostat was around 195, and the engine ran hotter than it does now. As I recall up to 220 degrees. As I live in South Florida I wanted to get a head start on the heat build up.

Jim
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