Coolant Temp??

[1 Bad CJ5]

Running a late 70's Chevy 400. Has a stock 195* T-stat. 3 core radiator (not aluminum). no fan shroud, stock chevy fan.

It will run consistantly around 200-210. A couple times in low gears at lower rpm while climbing a trail it starts to creep up into the 220-230 range. Driving down the road it does fine, and in stop and go traffic when it gets to 210 it immediately drops back down to 195-200 from the thermostat opening. I know its not overheating, but if I can keep the temp lower, I want to. I dont want to run at the limits, I want a cushion if possible. At what temp should I be concerned about overheating?

Plans to help the cooling system include, aluminum radiator, 180* T-stat, fan shroud, possibly a high volume water pump. Anything else you know of let me know, or if any of this wont be much help I would appreciate that info too.

 

[Torxhead]

I would first be interested in the cooling fan. A large 7 blade fixed type would be be good for low speed driving and a small fan with a clutch in good condition would be good for economy but run hotter. Another interest would be how long has it been since a quality flush out has been done. You should do the basics first before putting in the fancy stuff.

 

[Turbogus]

Back in the mid 80's I was running a K5 Blazer with that 400 and a THM 400 Transmission . This beast ran a SIX row radiator, as it was also equipped with A/C. She always kept her cool but developed a leak and after rodding out the core was kaput. $500 for the replacement core in 1980's dollars was a helluva bite but she kept her cool until I sold her. This Blazer had a full time 4 wheel drive and I was running Buckshot Wide Mudder P78-15's ~she actually looked lifted but it was stock suspension.

All this being said I'm gearing up for the Contour/Mystique double fan upgrade. Struggling with finding high amp relays and pigtails right now though.

 

[dauntless89]

At what temp should I be concerned about overheating?

As I understand it, overheating occurs when the engine heats up above the boiling point of your coolant. When you start getting cavitation in your block (where there's an air gap between the coolant and the metal) heat transfer is inhibited to the point that the coolant can't suck the heat out as fast as the engine is generating it, at which point the block temp will rise indefinitely, regardless of airflow through the radiator, t-stat, etc. Blown head gaskets, bearing damage, and even engine seizing may ensue.

Straight water at no pressure will boil at 212* at sea level
50/50 at no pressure will boil at 223* at sea level
50/50 at 12 psi will boil at 260* or so at sea level
50/50 at 16 psi will boil at 271* or so at sea level

Reduce your boiling point temperatures by about 1% for every 1,000 feet ASL you are. I'm running 50/50 at 12 lbs, home is at 3,200 ft and I wheel no higher than about 6,000 ft. 3.2% of 260 is 8.32*, 6% is 15.6*. That puts my real-life boiling point between 244* and 252*. I'm running a 195* stat but my cooling system is overkill for my motor. I've never seen it get higher than the rated thermostat temp.

Where are you measuring from? If you're measuring 230* at the thermostat housing, I would say it's probably fine, but you have no cushion. A cooler thermostat would give you the comfort zone you're looking for. If your normal is 200-210, and max is 230* with a 195* stat, you'd probably see a normal of 185-195, and a max of 215* with a 180* stat. Just about ideal IMHO.

I would run as high a pressure cap as you can and get a 180* stat and see where that puts you. After that, if you want more cushion, put in a shroud. Directing airflow through the radiator is free efficiency after all. Then, if it's still not cutting it look into more expensive things like better radiators, bigger fans, etc.

That's what I would do anyway. Hope that helps!

 

[1 Bad CJ5]

Dauntless Buick 225 V6 that was awesome. Home for me is at 5200, and I wheel above 12,000 sometimes. Mostly down around 10,000 tho. If I am at 12,000 12% of 260 is 31, so boiling temp is 229 at 12,000 feet, 234 at 10,000 ft. So yeah, I am right on that threshold. A 16lb cap will put me at a 238 boiling point at 12,000 feet and 244 at 10,000 ft. So I will definitely be putting a 16lb cap on my radiator, and I will try the 180* stat.

 

[Turbogus]

Found my relay and socket, will fab my own pigtail from Amazon since the local homogenized shops were of no help. Dam I miss the old Mom n' Pop auto parts/machine shops.

 

[duffer]

My house sits at 5300 feet and a lot of the wheeling we do also is in the 9000 to 10,500 ft elevation.

You want a 16 lb cap, FlowKooler 1880 water pump (a bit pricy but really do work), 7 blade straight mechanical fan, 2 row aluminum radiator (I am using a 19x26") and a TIGHT fitting shroud. I run a 50-50 antifreeze mix with a Royal Purple "wetter".

That arrangement may cost you a little fuel efficiency loss, but can't be beat for cooling a big sbc. I know the later small blocks all run 205-210 thermostats but that is way warmer than I like running when turning low rpms under high ambient temps. I try to keep things in the 180-195 range.

I also run big block oil pumps in all my small blocks with the bypass set at 60 lbs. That gives you full oil pressure at 500 rpms and 195 degrees.

 

[duffer]

One more thing to think about: If you get it set up where you are moving a lot of air through the radiator, that air has to have an easy exit. I run a vented hood on the 3B and it also has a lot of "vent" area around the fender well dump headers. You can actually feel the air flow around the headers.

 

[tarry99]

Running a late 70's Chevy 400. Has a stock 195* T-stat. 3 core radiator (not aluminum). no fan shroud, stock chevy fan.

It will run consistantly around 200-210. A couple times in low gears at lower rpm while climbing a trail it starts to creep up into the 220-230 range. Driving down the road it does fine, and in stop and go traffic when it gets to 210 it immediately drops back down to 195-200 from the thermostat opening. I know its not overheating, but if I can keep the temp lower, I want to. I dont want to run at the limits, I want a cushion if possible. At what temp should I be concerned about overheating?

Plans to help the cooling system include, aluminum radiator, 180* T-stat, fan shroud, possibly a high volume water pump. Anything else you know of let me know, or if any of this wont be much help I would appreciate that info too.

Bad CJ.................No Fan shroud...............Stop!.........get one on and your problem will go away. Air Flow through the core is the most important thing and the shroud will help force the column of air through the Radiator. ..................as far as percentage of Antifreeze and higher pressure caps they do raise the boiling point of the coolant......... but at a High Price to pay if your running your coolant at 210-240 on a regular basis. High water temps will cook your engine oil to a point that it breaks down its ability to do its lubricating job.
Having the ability to allow your system to go to 240 for short periods of time is just a safety feature and should not be considered as a fix for a substandard system.

 

[1 Bad CJ5]

Duffer thanx for the info on what you have in your set up that works. I hate it when people keep telling me that "its up to me". Hell, I wouldnt be asking for help if I knew what I wanted to do. And Tarry, I have never hit 240. I have only been close to 230 once or twice. Normal driving will be between 200-210, with the 210 being more city stop and go and the 200 on highway with air being pushed into the engine. About the fan shroud...I cannot find one that fits. I have been to a local jeep salvage yard with CJ's and every shroud I find is 22-24 inches, and I need a 26 incher. Any ideas on what has a 26 inch shroud with a center mount fan? I found a couple large shrouds but they had offset fans.

 

[TroyaCantrell]

Check this site if you haven't. It is local to me here in sac and they don't come up often on google searches but the specialize in jeeps and might have a shroud for you. They had a couple last time I was over there and they will ship.

http://www.jwjeep.com/

 

[duffer]

If you can't find a shroud that fits, they are not that difficult to make. If you have access to a box and pan brake, it is a piece of cake.

Make a good cardboard mock up and mount it. Trace fan outline with a sharpie and give it about 3/4" clearence. Rule of thumb for depth is you want blades half in/half out. Sheet metal shop could bend it up from your finished mock up. 20 to 26 gage steel works, but aluminum is lighter and looks better. I use 0.063" 5052 aluminum and if you want some shine, just polish it. Not easy to get pics of the one in the 3B-stuff is cramed in pretty tight.

 

[tarry99]

Duffer thanx for the info on what you have in your set up that works. I hate it when people keep telling me that "its up to me". Hell, I wouldnt be asking for help if I knew what I wanted to do. And Tarry, I have never hit 240. I have only been close to 230 once or twice. Normal driving will be between 200-210, with the 210 being more city stop and go and the 200 on highway with air being pushed into the engine. About the fan shroud...I cannot find one that fits. I have been to a local jeep salvage yard with CJ's and every shroud I find is 22-24 inches, and I need a 26 incher. Any ideas on what has a 26 inch shroud with a center mount fan? I found a couple large shrouds but they had offset fans.

1 Bad..........what kind of radiator? Sometimes you have to find one thats close and add to the side's with a strip of aluminum pop-riveted to the edges to fill in the gaps.

If nothing else, if you have someone near you into sheet metal..........you can roll the cylinder to the fan size you need and build the side skirts and attache it to the radiator brackets.