TO SHROUD OR NOT TO SHROUD ELECTRIC FAN?

[Weldguy]

I've decided to go with an electric puller fan when putting my '70 Challenger (440, auto) back together. I'm trying to decide on a fan with or without a shroud. The ones I've seen without a shroud seem to have a narrow band around the outside of the fan blades. Would that style (without shroud) allow more air to pass through the triple-core radiator at highway speed? Would a full shroud pull more air around town and in stop-and-go traffic?
I decided to go with electric because I previously experienced it running close to 215 degrees in traffic with the factory fan (no clutch) and also with a Flex-fan. I felt part of the problem was with running a 3200 RPM stall converter. This time, I'm running a 2400 RPM converter.
A combination aluminum radiator and electric fan combo is just out of my price range right now.

 

[Ricks72Chlgr440]

I've decided to go with an electric puller fan when putting my '70 Challenger (440, auto) back together. I'm trying to decide on a fan with or without a shroud. The ones I've seen without a shroud seem to have a narrow band around the outside of the fan blades. Would that style (without shroud) allow more air to pass through the triple-core radiator at highway speed? Would a full shroud pull more air around town and in stop-and-go traffic?
I decided to go with electric because I previously experienced it running close to 215 degrees in traffic with the factory fan (no clutch) and also with a Flex-fan. I felt part of the problem was with running a 3200 RPM stall converter. This time, I'm running a 2400 RPM converter.
A combination aluminum radiator and electric fan combo is just out of my price range right now.

Lots has been written about the electric fan or mechanical, shroud or no shroud. It's pretty hard to beat the OE design where there was a mechanical fan, fan clutch, and plastic shroud that covered the engine side of the radiator. Those OE fans have a nice pitch to the blades and actually move a ton of air. There is limited space between the radiator and the front of the engine, but Chrysler did it way back when. You may want to research what Ma Mopar used and try to replicate it. I assume you're using an OE style 3 core radiator.

Most of the issues I've seen with aftermarket electric fans and aftermarket shrouds is that the fans don't move enough air. At low speeds the don't move enough air and at highway speeds actually inhibit airflow through the radiator when there should be plenty of airflow. Without a full shroud the fan cannot force air through the radiator so you're not going to get adequate cooling at low speeds. Our cars are going to get hotter as we sit in traffic. This is especially true of we use A/C. The question is if the temp comes back down as we start moving again. As to the higher stall converter, I installed a large cooler in front of the radiator and did not use the cooler in the lower radiator tank. No need to pre-heat the engine water with trans cooling! Did this on both my 70 duster with a 408 & 3500 stall converter and my current Challenger with 440 and 2800 converter. No issues.

 

[Xcudame]

I agree with Rick (again!). It's really hard to beat the cooling efficiency of the factory clutch fan and shroud. All the big block cop cars used clutch fans and shrouds, especially in the 70's when saddled with smog pumps, catalytic converters and lean burn electronics! They idled a lot and never puked out coolant! I prefer that odd asymmetric 7 blade fan with a clutch. And a nice big transmission cooler not connected to the lower radiator is great too! Keep the trans fluid cooling separate from the engine coolant!

As I posted earlier on another post, with a 16 psi radiator cap, water doesn't boil until 250+ degrees Fahrenheit, so spikes periodically to 220 don't concern me unless the temperature doesn't come back down with in open air and normal speeds.

 

[moparleo]

The guys above are on the money. It is only when guys try to "improve " their cars that problems pop up.
The factory cooling system was more that up to the task over 50 years ago.
If your engine or tor1ue converter are non factory, you can expect other things to change as well. The domino effect.
Don't try to redesign the cooling system. Look in the factory service manual in the cooling system section for the exact specs of the fan blade, fan clutch type , shroud, thermostat, cooling system pressure, thermostat etc..The fans job is only to pull enpugh air through the radator core to shed heta below 40mph, Speeds faster than that move more air just by ram effect, the fan is usually disengaged.
A very good, "modern" upgrade is a coolant recovery system. The main difference is in the cap. The recovery system uses a 2 way valve in the cap that allows coolant to exit into the recovery tank at high temp and than opens again when the system goes into vacuum as the coolant cools down, refilling the radiator.
This keps the radiator full at all tempratures and you don't have to keep topping the coolant every time it warms up and loses a small amount of coolant out the overflow.

 

[heminut]

Another thing, if you still have that flex blade fan throw it in the trash and don't look back! They aren't very efficient at all and they are dangerous! I have a nephew that lost an eye from a blade coming off of one of those things. The Dr. told him that if he hadn't been wearing glasses it might have killed him!

 

[moparleo]

Absolutely. I had a flex fan many years ago and it took out my new radiator. Junk, inefficient and potewntialy dangerous.