Fan Blade Question

Like the others have mentioned, a well fitted shroud can make a big difference. I ran without a shroud for years because I didn't have one and folks hadn't yet started reproducing the factory-style V6 shrouds. We ended up adapting and customizing an F-Head shroud to try to help with the low speed heating issues and it helped. I also run a "high-flow" Robertshaw 160 degree thermostat.

 

A couple of things.
First verify your temps with an IR gauge.

I run a 5 blade stock Ford 3/4 ton flex fan with a home built shroud and, at idle, can feel the fan pull at my shirt/overalls when I lean over the grill. The shroud is a simple piece of tin bolted to the radiator flanges which extended the edge of the "tunnel" past the fan blades. It has never topped 190 except for the initial thermostat opening.

Remember, high timing, hot(er) cams and higher compression pistons will all build heat.

Generally, higher temp thermostats will run closer to the thermostat rating. I prefer 180's or 195's if available.

 

This brings back nightmares. For a couple years I fought with overheating just as you describe. My solution was to move the trans cooler that sat in front of the radiator. (probably not applicable to your setup)

I run a Champion 3 core, standard thermostat, 6 blade flex fan, stock fiberglass shroud. Fan sits about 2 inches away from radiator and just clears belts. I have the heater core lines blocked on my Offenhauser manifold and this doesn't seem to make a difference. I bled any air from the top of the manifold. I checked thermostat in boiling water. Stock timing & cam. I think the stock system is underbuilt any little thing can cause outa control temps.

I also went through a period of where I would have a lean condition when it started to vapor lock. That was another nightmare that I finally figured out. Temps would climb when it went lean.

 

Played with the JEEP today.

This was at an idol with no shroud. It’s drawing air through the radiator pretty good.

ran this through the radiator and engine to see if would help. The system was pretty clean no rust or dirt and looked pretty clean.

 

.
20 minutes idoling in drive way about 72* out

 

This was idling around levee in low gear after about 15-20 minutes.

kick on the electric fan…dropped temp about 5* in less then a minute.

 

I have confirmed the temps with my hand held.
I’ve considered that the build itself , with the higher compression, over size pistons, bigger cam and running a little more advanced timing is contributing to the temps. It just makes me nervous when the temps start climbing.

 

I pulled the radiator out and bolted the fan shroud to it. I’m thinking about cutting it up and extending it down and closing in the bottom.

 

Looking at where the fan sits inside the shroud it is inside it about an inch deeper then the outside lip. Thinking about trimming it back so the fan is sitting outside the shroud about an inch.

 

For those that were wondering about a 7-blade fan, I run a 7-blade out of a Waggoner with the clutch and a homemade fan shroud. I'm running a late model CJ grill with a old OEM V8 3-core copper-brass radiator. It only builds heat when I on the highway/freeway which I've found to be the issue of not being able to get rid of the hot air under the hood. I proved this theory buy running a 1" spacer under my hood hinges to improve air flow. I'm running a stock 225 with cast iron manifolds, 31" tires and 4.10 gears.

 

This.

What if you were doing all this worrying over a miscalibrated sensor or a poor wire connection?

Precision is not accuracy.

 

I installed an OEM Jeep 7-blade fan on my Dauntless last year, and it pulls a great deal more air and cools noticeably better than the previous OEM 5-blade fan did.

As a comparison, the 5-blade fan has a total of about 73 square inches of blade area, while the 7-blade fan has approx. 132 sq. in. of total blade area - nearly twice that of the 5-blade.

Here's a writeup I did on the 7-blade fan: http://www.earlycj5.com/xf_cj5/index.php?threads/156120/

 

Originally I was running stock water pump and it was running 10* warmer when I was running trails or around town in stop and go traffic. I switched to the Flow Kool and it has made a noticeable difference. I’m just trying to figure out if I can get the temps to stay down with the bigger fan.

 

I verified this with my infrared thermonitor. My gauge is reading accurately.

 

Maurywhurt, this is where I got the idea/information to go to the 7-blade. Thanks for the write up.

 

I'll offer my advice as a retired sheet metal worker and someone that understands air flow.
Your fan blades should be about halfway into your shroud. That's a depth advice. Not completely inside the shroud and definitely not outside the shroud.
Additionally, the tips of your blades should be 1/2" to 3/4" from the circumference of the round portion of your shroud.
Those two dimensions will optimize your fan's ability to pull air through the radiator.
Your symptoms seem to indicate poor airflow through the radiator at low speeds since your highway temperature is fine.
Lastly, ABSOLUTELY enclose the bottom of that shroud. Jeez, what were the Jeep engineers thinking? The shroud needs to encapsulate the fan so that the fan can ONLY draw air through your radiator.

 

Ahhh, the statistician. Part of my job at the U was looking at data sets from superfund sites (EPA contract) to see how tightly controlled they were produced, and to compute the accuracy and precision. Yes, two very different things.

One final easy thing to do with this is add a water wetter. That stuff actually works. I use Red Line's. It was good for about a 5 degree decrease in temp with all else remaining the same.

 

I bought a bottle the other day when I was in the parts store, gonna give it a try.

 

I'm not getting this. Did you mean to say the tips of the blades …?