Anything in front of the radiator is a potential obstruction to the airflow over the fins of the radiator. The closer it is to the radiator, the more flow is obstructed especially at speed.

The fan works best to 'assist' in getting air to flow over the fins (usually when the momentum of the vehicle is not sufficient) not as the primary means of flow. At speed, a front mounted fan would have to run to compensate for the flow restriction it creates versus an open radiator. Overall, not the most efficient use/placement of a fan on a radiator moving through air (unless your car spends most of its time sitting in stop-n-go traffic).

 

ha ha that was a big thing in the late 70-early 80s. just got a good chuckle out of it.
those worked on an electrical thermostat so they only ran when under hood temps got to say 220-230 F then they kicked on. similar or basically the same as you would see today on a new civic or accord.

imo a waste of time and money on a classic as the rads are big enuf and if in good shape will cool almost anything.

maybe he had some HP mods that he was worried about but imho for an otherwise stock motor forget it.

 

I haven't heard of a mechanical fan and an electric fan. My only thought is that it could be to help cool it at idle, since the mechanical fan will be spinning slower.

I have, however, heard of people putting two electric fans, one on either side. But I don't see the reasoning. I'm not 100% sure since I have never experimented with this or done any scientific tests, but I don't think it's effective. The reason is, suppose you have two 1800 cfm fans, one on either side. Will that move 3600 cfm? No it will still only move 1800 cfm since that's just how much airflow each one can put out.

If you had a 1200 cfm pusher on the front, and an 1800 cfm puller in the back, most likely the 1200cfm pusher will just become a blockage for the 1800 cfm puller.

Just my $0.02.

 

All,

On the Power Tour this year one of the gentlemen in the pack I was with (72 Dodge Challenger) had the original engine and stock fan setup but also had a electric fan in front of the radiator. This was the first time I'd ever seen both mechanical & electric fan setup on a car.

I looked at 1,000's of cars in 7 states during this trip and not another one had both setups. What's the draw back? Seems it would only be a benefit especially if you have cooling issues with the mechanical setup to begin with? If you have the space upfront, why not install both?

Well.......we have both. 302 with aluminum heads,intake and a mild cam. Large 2 row alum Northern rad. Last yr in a parade we hit 220' on the mech. gauge and decided to fall out of the parade. Within 3 minutes of 40 mph driving the temp got back to 180' or less. clearly it was a low speed issue for us. I installed a 16" fan INFRONT of the rad. A few wks later we were driving along at 55 mph on a secondary road with the temp at ~180' and came up to construction that had us stopped rather quickly and held us for 5 min. Temp climbed right up to 210' where the electric fan kicked on and started to cool us back down. Once moving along the fan reached the lower limited and shut off--just as it should. In our case, the fan solved our low speed temp issues and doesn't seem to adversely effect airflow at speed. Just my experience.

 

Well.......we have both. 302 with aluminum heads,intake and a mild cam. Large 2 row alum Northern rad. Last yr in a parade we hit 220' on the mech. gauge and decided to fall out of the parade. Within 3 minutes of 40 mph driving the temp got back to 180' or less. clearly it was a low speed issue for us. I installed a 16" fan INFRONT of the rad. A few wks later we were driving along at 55 mph on a secondary road with the temp at ~180' and came up to construction that had us stopped rather quickly and held us for 5 min. Temp climbed right up to 210' where the electric fan kicked on and started to cool us back down. Once moving along the fan reached the lower limited and shut off--just as it should. In our case, the fan solved our low speed temp issues and doesn't seem to adversely effect airflow at speed. Just my experience.

So why not just ditch the mechanical fan and install the electric as a puller? Seems that in your case, the only time you have an issue is at reduced speeds when you don't have enough airflow over the fins. Then the electric fan would still come in when needed. Just a thought maybe you could test.