Mechanical Vs Electrical Fans For Efficient Cooling At Idle

Discussion in 'Cooling Systems' started by jelco, Dec 16, 2020.

  1. jelco

    jelco Active Member

    Cast a vote for Mechanical vs Electrical fans for a sbc 350 daily driver with air conditioning that experiences stop and go traffic in Arizona summers with temp greater than 110F. Which set up would most effectively keep the engine <190F and have ice cold a/c at idle?

    I think the answer would probably be a thermal fan clutch with an electric fan pusher in front of the radiator but I don't think I have room for that in a 1964 El Camino. I've seen the dyno results for mechanical fans (loss of 12hp with a thermal fan clutch) but an argument for mechanical fans is greater CFM and lower cost. There are many advantages for dual electric fans. You can get a decent set up for $500 from 'cold case'.

    I bring this up because I have a thermal fan clutch and radiator that I can install and would like to save money for $1500 vintage air conditioning or $1,000 dakota digital gauges.

    Link discussing how to properly set up mechanical fans.
  2. JohnHancock

    JohnHancock Well-Known Member

    I think I saw somewhere a fan behind the radiator was most affective. Check that out.
  3. jelco

    jelco Active Member

    A fan between the radiator and engine is most effective. It pulls air through the radiator towards the engine. At highway speeds the fan doesn’t do much.
    A second fan between the grill and radiator would push air through the radiator fins towards the engine.
    At least this is how it was explained to me.
  4. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

    adding an oil cooler and if its an auto transmission a trans fluid cooler to the car, helps to reduce the thermal load on the radiator.
    its oil that cools most of the hotter parts so cooling oil helps a great deal, and removes much of the fluid temp build-up, the radiator is forced to deal with.
    as a result you ,if you add a decent sized fan equiped remote oil cooler,
    you can generally knock about 15%-20% off the thermal heat load on the radiator ,
    thats a significant improvement.
    use of a well-designed fan shroud, and a mechanical clutch fan or dual electric fans properly mounted in that shroud,
    behind the radiator to increase fan efficiency can easily drop the coolant temps enough,
    to make a very noticeable difference in the engine operating temperatures.
    many modern cars use dual electric fans, but obviously both the fan(s) and shroud needs to be carefully selected to match the application.
    yet one of the biggest improvements will be in increasing the effective surface area of the radiator if you have that option.
    measure the area height width and depth or thickness of the area the radiator mounts in , in the car/truck accurately so you can gauge your options, be aware of mounting flanges and the need to access drains and connections and you might want to visit a local salvage yard,
    or order an aftermarket radiator the difference in cooling efficiency can be dramatic as most stock radiators are barely adequate if in good condition.
    personally ID prefer to use a mechanical fan with a thermal clutch if theres room.


    related threads and sub linked info.:D
    Last edited: Dec 16, 2020
  5. jelco

    jelco Active Member

    Thanks for the reply and info. Why do you prefer a mechanical fan with thermal clutch over electrical fans?
  6. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

    either system works if properly installed ,
    each system has advantages and disadvantages,
    but the engine-driven clutch fan is a bit simpler,
    and if you have the room, clearance,its more basic,
    easy to diagnose if problems do develope,
    and a bit less likely to develop durability issues in my experience
    jelco likes this.
  7. Indycars

    Indycars Administrator Staff Member


    If you go with an electrical fan, then you need a alternator that can keep up at a slow idle rpm. Alternators have
    a very low output at idle, which is the very time you need it the most ..... stop light or stop and go traffic.

    That is why I have a CS-144 alternator instead of the 1o-si that I started with. So check out the graphs below.....
    what alternator do you have ???

    BTW, the graphs are in alternator RPM, not engine RPM. You should measure your pulleys, but typically
    you can figure the alternator is spinning at 2.5 times the crank RPM.

    Notice the output of each alternator at your idle RPM

    Last edited: Dec 17, 2020
  8. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

  9. Indycars

    Indycars Administrator Staff Member

    No problem, I've had it for years now !
  10. JohnHancock

    JohnHancock Well-Known Member

    Wonder if I can get enough output from one of those real small diameter alternators.
  11. Mark Bradley

    Mark Bradley Da guy in Newbury

    You really cannot debate consistent confirming data and Grumpy keeps shelling it out.
    I went to a properly fitted clutch fan and shroud and can drive my 496 in traffic all day.
    I run 8 qts of oil although I will likely add an oil cooler for low cost insurance. I also run an oil temp sensor and as long as the oil is cool (<230°) I’m golden.
  12. jelco

    jelco Active Member

    I haven’t purchased the alternator yet but I’m thinking about getting a 1992 camaro 140amp from O’Reilly’s or

    Another question...
    Is it better to have the upper radiator hose attach on the driver’s side?
    If I use the 19464 el camino radiator from coldcase, the upper hose attaches on the passenger side, same side as battery. If I use the 66 radiator, the upper hose attaches to the driver side, same side as alternator. Is it just preference or could there be another reason?
    Since I’m using brackets and serpentine setup from a 92 Camaro I thought it may be good to set it up like the camaro, which has the upper radiator hose on the driver side.

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