Daubies at home HEMI conversion
- Thread starter Daubie3
- Start date
Yes, the fan and clutch are directly off of the 05 4.0 that was in the Jeep. It spun right on...
These are the best pictures I have right now.
The problem with CFM measurement is just that - how it is measured. Many cheap fans can claim 2700, 3000 cfm if they are measured at 0 static pressure - meaning sitting in the open air. Put that same fan in front of a radiator, and a condenser, and other coolers, and those fans often do not have the power to maintain that air flow. A better measurement is usually amperage. More amp draw means more power, and therefore better ability to move more air at higher static pressure.
The first fan I used (which I purchased from Red Rock) was rated at 2700 cfm - but drew only 10 amps, 120 watts. It was grossly under powered and would not cool the Hemi.
Spal provides static pressure graphs for all of their electric fans, showing how the CFM changes / drops as static pressure increases. More CFM at higher static pressure is what you are looking for. Cheap fans do not provide this info, they just drop the CFM number for the wow factor.
No way to tell from these specs how your fan will perform. What size fuse, or wire gauge does Flex recommend for this fan? That would be at least an indicator.
What you have to find out is what the CFM rating is at load. This is what @NashvilleTJ found out with his old fans. The SPAL fans have a chart that shows what they pull at load.
Edit: Beat me to it... Plus yours is a better explanation.
I should add, I had that Black Magic fan on my Magnum swap when I had the 5.2 and it worked great and kept my temps right at 210* all the time until I cracked my head. So it isn't a "bad" fan. But the SPAL fans are leaps & bounds better. Plus the SPAL fans are brushless which means less amps needed to power them. But they aren't CHEAP and you also need their temperature sensor to control it with.
OK - For science (copywrite credit to @jjvw )...
Now granted, this is a sample of 1. And although not even close to being in @sab 's engineering league, here is my shot.
I took the rig out for a drive on the highway to test the no fan needed theory. Normally around town, the Hemi stays very consistently right around 183. The ambient temp today is 93. As expected, this is the engine temp during a 20-minute drive (under 40 mph) out to the highway (this is an autometer ODBII gauge running on my phone):
Normally running on the highway, it runs up to about 190, or a bit above. So I hit the highway, nice and flat, and 70 mph. This is the consistent reading after running about 20 minutes.
At this point, I hit the switch to turn off the fan. After a minute or two, it started climbing. After 3-5 minutes it hit 220, and was still climbing:
Now I'm dedicated to you boys and all, but I'm not overheating the rig just to make a point - not even for science!
So I turned the fan back on, and it slowly leveled out and began to fall. After perhaps 5 minutes it was back down below 200:
And after another 10 minutes or so, it was back down close to 190:
At this point, I shut off the fan again to validate the result. Which was the same.
So at least in my rig, with my setup, the fan has to be running on the highway to keep the big mill cool. Again, sample of 1, but I'm sure not gonna be turnin' my fan off while runnin' down the hghway any time soon...
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Jeff:
I don’t know if your rig has A/C or not, but if so, was your A/C on the entire time of your testing? The condenser’s heat transfer can really affect radiator performance. I have a car with a crappy aftermarket radiator, and it performs so much worse than the OEM one (no longer available) that when ambient temps are in the high 90s or above, I have to turn the temperature control down to keep the car from overheating, and this only occurs at road speeds above about 70MPH.
I don’t know if your rig has A/C or not, but if so, was your A/C on the entire time of your testing? The condenser’s heat transfer can really affect radiator performance. I have a car with a crappy aftermarket radiator, and it performs so much worse than the OEM one (no longer available) that when ambient temps are in the high 90s or above, I have to turn the temperature control down to keep the car from overheating, and this only occurs at road speeds above about 70MPH.
That's interesting. I've driven a few cars with no fan, and the only issue was you couldn't stop or creep along. They were fine as long as the air was moving with some speed.
I have A/C, and it was off. Neither here nor there for this, but with the A/C on, there is a relay which overrides the fan controller, and the fan runs constantly. My OFF-bypass is wired such that it turns off the fan even with the A/C on.
This thing puts almost 400 ponies to the tires on the dyno (to the 40" tires...), and as a result it makes a crazy amount of heat. Again, I may be a sample of 1 here.
I've got to add a Kill Switch to my fan. Thanks for reminding me. I've got one position for overriding the fan to come on 100% wired in but forgot the kill switch for fording.
Add it to my To Do list.
OK - For science (copywrite credit to @jjvw )...
Now granted, this is a sample of 1. And although not even close to being in @sab 's engineering league, here is my shot.
I took the rig out for a drive on the highway to test the no fan needed theory. Normally around town, the Hemi stays very consistently right around 183. The ambient temp today is 93. As expected, this is the engine temp during a 20-minute drive (under 40 mph) out to the highway (this is an autometer ODBII gauge running on my phone):
View attachment 553983
Normally running on the highway, it runs up to about 190, or a bit above. So I hit the highway, nice and flat, and 70 mph. This is the consistent reading after running about 20 minutes.
View attachment 553988
At this point, I hit the switch to turn off the fan. After a minute or two, it started climbing. After 3-5 minutes it hit 220, and was still climbing:
View attachment 554017
Now I'm dedicated to you boys and all, but I'm not overheating the rig just to make a point - not even for science!
So I turned the fan back on, and it slowly leveled out and began to fall. After perhaps 5 minutes it was back down below 200:
View attachment 554011
And after another 10 minutes or so, it was back down close to 190:
View attachment 554013
At this point, I shut off the fan again to validate the result. Which was the same.
So at least in my rig, with my setup, the fan has to be running on the highway to keep the big mill cool. Again, sample of 1, but I'm sure not gonna be turnin' my fan off while runnin' down the hghway any time soon...
That's pretty good science Jeff; A testable question with one variable and repeatable results.No point in letting the thing melt down so as to be able to fully document the problem (unless you also were going to rebuild it and do it again so you could validate the data
)
That's a good reason to go ahead and supercharge that thing.... I mean it only makes sense, more air flow has to make it cooler...right.?.?
I'd always been under the assumption that once you were above a certain speed that the fan wasn't needed anymore either. This might apply to stock rigs? We'll have to see what mine does once I've got it running.
Me too. I know on some of the 3/4 ton trucks I owned in the past the fans would lock up when needed and freespool at times, normally when moving faster.
This was the whole point of the fan clutch idea as I understood it. I'm OLD so I had many cars with a direct drive mechanical fan. When they came out with the fan clutch it was supposed to free up HP when the fan wasn't needed anymore.
Back to @AjordanH questions. I'm wondering if it's not either your fan or your radiator size that is causing your overheating issues. Now since you don't overheat when idling I'm guessing that your radiator is OK so then I'd be looking at your fan. But I'd also eliminate any other possibilities prior to messing with your fan. If you have the room to install a mechanical fan I'd go that route first just make sure you have a shroud installed also.
As suggested make sure you don't have any air pockets. I chased a overheating issue on my old Magnum engine that turned out to be a cracked head that was putting exhaust heat into my cooling system.
Good luck on finding what's wrong and hopefully you'll figure it out soon as I know how frustrating it can be.
Thanks for that “science experiment”. It really makes me think (hope) the electric fan is the problem. I rounded up the pieces to put the 4.0 fan and clutch on the Hemi, including the original shroud. I measured my radiator core at 2.625” thick but I don’t know if it is a 2 core, 3 core or what. I think I’ll have room for the mechanical fan. Maybe. On a side note I figured I’d try something quick and easy so I plugged in the laptop and forced it in open loop and added 20% to my VE tables above 1200rpm to make it really rich when cruising at 2200rpm and went for a drive. Within 5 miles at 60 mph it was 235 degrees. I may try advancing the timing today before I tear into the fan and shroud. The only other vehicle I had do something similar to this was a 305 Camaro. It would run fine at 40mph but if was running highway speeds (60-70) then it would overheat. It was a bad head gasket. I really hope my newly rebuilt Hemi doesn’t have combustion gasses getting into the coolant 
. Thanks for all the help y’all.
. Thanks for all the help y’all.
Thanks for that “science experiment”. It really makes me think (hope) the electric fan is the problem. I rounded up the pieces to put the 4.0 fan and clutch on the Hemi, including the original shroud. I measured my radiator core at 2.625” thick but I don’t know if it is a 2 core, 3 core or what. I think I’ll have room for the mechanical fan. Maybe. On a side note I figured I’d try something quick and easy so I plugged in the laptop and forced it in open loop and added 20% to my VE tables above 1200rpm to make it really rich when cruising at 2200rpm and went for a drive. Within 5 miles at 60 mph it was 235 degrees. I may try advancing the timing today before I tear into the fan and shroud. The only other vehicle I had do something similar to this was a 305 Camaro. It would run fine at 40mph but if was running highway speeds (60-70) then it would overheat. It was a bad head gasket. I really hope my newly rebuilt Hemi doesn’t have combustion gasses getting into the coolant
You can get the test kit to find out if you have a blown head gasket or other issue putting combustion gasses into your cooling system.
https://www.amazon.com/Block-Tester-BT-500-Combustion-Leak/dp/B06VVBSFTF/?tag=wranglerorg-20
On my Magnum once it warmed up you couldn't take the radiator cap off or it'd blow the coolant out of the radiator so I couldn't test it.
Thanks for that “science experiment”. It really makes me think (hope) the electric fan is the problem. I rounded up the pieces to put the 4.0 fan and clutch on the Hemi, including the original shroud. I measured my radiator core at 2.625” thick but I don’t know if it is a 2 core, 3 core or what. I think I’ll have room for the mechanical fan. Maybe. On a side note I figured I’d try something quick and easy so I plugged in the laptop and forced it in open loop and added 20% to my VE tables above 1200rpm to make it really rich when cruising at 2200rpm and went for a drive. Within 5 miles at 60 mph it was 235 degrees. I may try advancing the timing today before I tear into the fan and shroud. The only other vehicle I had do something similar to this was a 305 Camaro. It would run fine at 40mph but if was running highway speeds (60-70) then it would overheat. It was a bad head gasket. I really hope my newly rebuilt Hemi doesn’t have combustion gasses getting into the coolant
Keep a few things in mind, 1- a fresh engine will run hotter during break-in, 2- lean runs hot, but too rich will wash the walls.
Thanks for that “science experiment”. It really makes me think (hope) the electric fan is the problem. I rounded up the pieces to put the 4.0 fan and clutch on the Hemi, including the original shroud. I measured my radiator core at 2.625” thick but I don’t know if it is a 2 core, 3 core or what. I think I’ll have room for the mechanical fan. Maybe. On a side note I figured I’d try something quick and easy so I plugged in the laptop and forced it in open loop and added 20% to my VE tables above 1200rpm to make it really rich when cruising at 2200rpm and went for a drive. Within 5 miles at 60 mph it was 235 degrees. I may try advancing the timing today before I tear into the fan and shroud. The only other vehicle I had do something similar to this was a 305 Camaro. It would run fine at 40mph but if was running highway speeds (60-70) then it would overheat. It was a bad head gasket. I really hope my newly rebuilt Hemi doesn’t have combustion gasses getting into the coolant
I don't know if it's even possible to put the head gaskets on improperly and maybe block some water passages. I know there are some engines where that's possible and can cause overheating issues..
Just a thought, probably not the case..
You might also drain and refill it again to see if maybe it does have some trapped air.. That alone can give you lots of problems.
Did you use one of those fill kits that's supposed to help purge all the air when you filled it this time.?
On the Hemi if you install the head gaskets upside down or on the wrong wide you'll have a coolant leak. So the answer is NO you can't install them incorrectly and block any coolant passages.