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post #1 of (permalink) Old 09-16-2003, 01:51 PM
jonestown
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optimal operating temp?

Ok guys I have been getting conflivting arguements on this question all be it from non cj owners so I thouhgt I would ask you all. Right now I have a 185 F new t-stat that sticks on me so I poked holes in two places to allow the coolant to open on the top side. (hope that makes sense) anyways what would be optimal temp t-stat on a 304. My gauge reads 190 most of the time and with thermal cool down she will reach 210. Is this to hot. My muscle car guys say this is good my 4x4 mud guys say its too hot. What do the cj guru's think. Thanks Eric [img]images/graemlins/confused.gif[/img]
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post #2 of (permalink) Old 09-16-2003, 02:19 PM
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Re: optimal operating temp?

Well, it might help if we knew what year vehicle you had, but 185* isn't too hot, it's probably too cold. For example the '78 FSM specifies a 195* thermostat. I think it's higher for late-models - 205* or 210*.

Cool is nice for humans, but engines want to be hot.

BTW, that's a hint, Son. Fill out your profile so we know something about you, your vehicle and how you use it.
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post #3 of (permalink) Old 09-16-2003, 03:28 PM
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Re: optimal operating temp?

Sorry Jim My profile is filled out or it is supposed to be. I'll go back and take a look and make sure. I didn't mean to ruffle anyones feather for I know how this board is about your profile ie; its a nice thing to do. Anyways it is a 1975 cj5 with a 304.Thanks Eric [img]images/graemlins/confused.gif[/img]
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post #4 of (permalink) Old 09-16-2003, 03:51 PM
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Re: optimal operating temp?

Hey, my feathers aren't ruffled - I'm too dumb to be insulted [img]images/graemlins/crazy.gif[/img] Just trying to help you help us help you. I think that's what I meant.

Anyway, I'm sure that your '75 will want a 195* thermostat. The higher temperature vaporizes fuel better for more complete combustion and better throttle response, speeds evaporation of water-based contaminants in the oil, and insures that the engine comes off the cold (relatively speaking) settings as soon as possible.

Many guys will put a colder thermostat in an engine that tends to overheat, but the stat doesn't have any significant affect on that. If an engine is going to get to 230* with the thermostat wide open, it doesn't make any difference whether it opened at 160* or 210*. The problem is that the engine is generating heat faster than the cooling system can get rid of it.

The higher temp thermostat might make the ultimate heat soak temperature a few degrees higher, but that won't hurt anything. And if you're worried about it, let the engine idle a few minutes in hot weather before you shut it off.

Don't listen to your mudding buddies. They're wearing their engines faster and not getting maximum performance out of them.
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post #5 of (permalink) Old 09-16-2003, 04:57 PM
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Re: optimal operating temp?

Thanks Jim appreciate your help. One more question for you I posted awhile back about hard "fuel" starting after it gets up to temp, thought it could be "vapor lock" and like you stated higher temp causes better fuel vaporization could that be part of my hard starting after I try to restart after coming to temp. I hope this all make sense I'm trying to type at work with distractions. Thanks again Eric
post #6 of (permalink) Old 09-16-2003, 06:19 PM
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Re: optimal operating temp?

Check you timing, it may be too far advanced. (I had that problem w/ my CJ when I first bought it)
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post #7 of (permalink) Old 09-16-2003, 07:01 PM
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Re: optimal operating temp?

I'd guess it's not vapor lock. Vapor lock occurs when fuel boils in the pump, because it can't pump vapor. If it were vapor locked, there would still be fuel in the float bowl. It would start easily, but then die after 10 or 15 seconds.

It's more likely that fuel is boiling out of the carb and puddling in the manifold, flooding the engine as soon as it starts to crank. Or boiling the carb dry so there's no gas to start on. Or, maybe most likely, it's boiling in the pump which is pushing it past a leaky needle valve and flooding the engine.

I'd check the easy things, like timing, and if it persists, do a quick rebuild of the carb and set everything to spec.

Also make sure the heat riser is opening. If it's stuck closed it can make the manifold under the carb very hot.
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post #8 of (permalink) Old 09-17-2003, 07:17 AM
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Re: optimal operating temp?

Wow, another somewhat local member. My in-laws live in Midway now but moved there from right on the border north of Gamaliel a year or so ago. Maybe we could meet someday.
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post #9 of (permalink) Old 09-17-2003, 10:46 AM
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Re: optimal operating temp?

Hey Will yeah that would be cool anytime your in the area let me know I'll see what I can do. If I can ever talk anybody from the area in to going to Hot Springs with me I'll give you a shout on the way down. [img]images/graemlins/40BEER.gif[/img]
post #10 of (permalink) Old 09-17-2003, 11:41 AM
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Re: optimal operating temp?

Yeah, I haven't been to hot springs since the park opened and would like to check it out. Keep me in mind.
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