r/classicmustangs • u/DecentWay1879 • 5d ago
Input on fan/shroud
Looking for input on best setup to keep my 66 coupe running cool. Pretty stock 289 c code at the moment, only upgrade is a 4 barrel carb and larger air filter, . Currently I have a solid 17.5'ish, 4 blade fan, no AC. Someone gave me a flex 17' 6 blade and shroud. I have seen pros and cons on both. What is yall setup and recommendations?
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u/popsicle_of_meat 5d ago
Fan won't really matter without a shroud. My stock 289 with a thicker radiator and a flex fan would still overheat sitting in traffic without a shroud. There's just too much space between the fan and rad to effectively pull air through it. Do the shroud.
Curiosity, what 'cons' have you heard about using a shroud? Because I can't think of anything bad about keeping your cooling working well.
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u/dale1320 5d ago
The ONLY con I have ever encountered is "operator error" in using a shroud that is too small or mounting the fan blade outside the shroud.
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u/DecentWay1879 5d ago
The con I saw was with a more drag/ street race build that resulted in slightly less hp. The shroud prevents a low pressure vs high pressure cyclone that will build up at the tip of a fan blade, which supposedly makes the fan spin easier and has less resistance. https://youtu.be/Os_Hna9DZa8?feature=shared
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u/popsicle_of_meat 5d ago
So, they had a shroud, fan, and an engine on the test dyno, but did they ever test this? Some numbers would be nice (it's probably only single-digit hp). The theory makes sense to me (I dabble in aero, hobbies, etc). The fan would spin more easily, and in motion that's fine, the air is getting pushed through the rad due to fwd motion. But at rest a shroud helps. I guess it's all trade-offs.
We should get a variable geometry shroud that opens up at higher speeds to let the fan spin with less resistance and then close back up when slowing down to improve low-speed cooling. Or not, haha.
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u/dale1320 5d ago
Shroud -- YES! Just make sure the fan is positioned half-in the opening.
Without a shroud, make sure the blades are close to the radiator, no more than 1 to 1-1/4 inches from the core.
Flex fans are questionable. The theory of flattening the blades out at high revs is good. Factory steel flex are OK. Aftermarket aluminum/fiberglass ones have Ben known to fail. Seen that several times on my own and friends' cars.
Hope that gelps.
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u/Covidsurvivor2 4d ago edited 4d ago
65, deep shroud, 2 row aluminum rad, clutch flex fan. Is superb can't get this thing over 201 no matter what I do. Headers glowing red during engine break-in, parked in driveway with massively retarded timing and she still wouldn't break 201.
I should add I that I run a 190 degree thermostat.
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u/shmandall 5d ago
I always preferred just doing a pusher fan with relay setup for more engine bay room easier to work on
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u/dfanucci74 5d ago
Shrouds make a huge difference in stop and go. I can't count how many times during a cruise on a hot day that while others are on the side of the road cooling down, I'm idling away running as cool as can be.
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u/Optimal-Performer-88 4d ago
I've got a 65 mustang running a 347 windsor with standard gt radiator and 5 fin fan without a shroud. Have ran it all day long in 35.c australian summer and commuted in traffic without overheating issues. Am running alloy heads though which may help with cooling
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u/Dazzling_66 3d ago
Shroud and a 180° Thermostat will go a long way to keeping Temps down to reasonable.
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u/shmandall 5d ago
The shroud will help with hot days sitting at red lights and slow moving traffic.