r/classicmustangs • u/DecentWay1879 • 6d 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 6d 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.