I am thinking of swapping out the flex fan on my 1969 Mach 1 for a clutch fan setup. There are pro's and con's for each. I would like to achieve more air flow at lower speeds. The engine doesn't overheat, but runs warmer than I like for a 1969 era car.
I've had some vehicles with a clutch fan setup and some with a flex fan setup. And even though a clutch fan always spins at lower RPM than the engine, because the clutch fan typically has a greater blade pitch and the blades are also rigid, they seem to move more air at lower RPM than a flex fan. I've thought of using the smaller diameter water pump pulley for A/C cars. But would prefer a fan change if that would help. Anybody have any thoughts on these two fan setup's.
Hey Mr Mike, I also have that same concern. Doesn't over heat but runs hotter than you would like at low speed cruising or if I have to idle for a few. My car, a no ac Cleveland had a small bolt to rad. support radiator and a fixed 4 blade fan. Laughable cooling system to say the least.
I tried to save some bucks and installed a 3 row bolt to support radiator and a flexolite 6 blade fan. That did help. But it still gets warmer than I would like on the really warm days 85 and up.
I think If you try to move the coolant faster it will not stay in the radiator long enough to cool.
I am very curious to here how you make out with that clutch and fan. That would be my last try before the big aluminum rad. with electric fan/fans with controller. Good luck cheers J
j-cobb9, Items that have helped so far on my car in order from most improvement to least improvement:
1) Largest aluminum radiator Griffin offers that are a drop in replacement.
2) Stewart brand high flow thermostat. The Stewart brand incorporates a few 3/16" diameter bleed holes which seems to improve cooling over other brand high flow thermostats. At least on my car.
3) High flow water pump. Regardless of brand. Also, changing from a stock 5 blade fan to a 6 blade flex fan helped about as much as the high flow water pump.
Before somebody asks, the head gaskets are installed correctly. I would still like it to run cooler. We'll see if a fan change again has any affect.
So j-cobb9, how many times did you cut yourself with that Flex-a-lite fan? Tried one once. I now use Derale brand flex fans. They are made from slightly thicker materials and fairly well deburred. Overall, seem to be a little better quality.
Thank you much for the quick input. Ultimately I think I will have to buck up for the bigger radiator. Before I wrestle with that fan again( one sliced knuckle and a very scratched up right arm ) I'll wait to here how you made out with yours. thanks again.
regards J.
I think I will try a clutch fan setup. I've researched and found the correct Hayden thermostatic fan clutch. Then both Derale and Flex-A-Lite offer fans to fit the clutch. Even if the cooling remains the same, it should require less Hp to operate.
mustangmike, the original fan on my car was a 5 blade flex fan. Over the years the blades would crack or break off. For that reason it's very difficult to find a good used or NOS original flex fan. I remember back in the early 1980's, part of a blade broke off one of those original flex fans on my older brothers 69 Mach 1. It damaged the plastic shroud so bad he had to remove it. Too bad they don't reproduce them (maybe in an improved version). If I recall, they moved more air than an aftermarket flex fan.
j-cobb9, you must have a Flex-A-Lite brand fan. Those things are razor sharp. Like I mentioned, from my experience the Derale fans are made much better and don't have razor sharp edges. Tried a Flex-A-Lite brand. Got it installed once with some cuts on my hands and arms. The second time I it went straight into the garbage can.
Hey guys, yes the flex o razor was just a temporary bandage, cheap and available at pep boys. I gained some more air flow and the car no longer sound like a p51 mustang as with that fixed 4 blade. Thanks for the input.
Mr Mike what size fan will you be trying ? 17 inch. 5 or 6 blade. Seems like that is the size for an ac car with a 379 radiator and a 24 inch shroud. Thanks for experimenting. Cheers John.
My car is a factory A/C car so it does have the 24" wide radiator. The original fan, which I don't have, was a 17.5" diameter 5 blade flex fan. All the aftermarket fans are either 17" or 18". Also, compared to OEM fans, the aftermarket stuff I have seen doesn't have as much surface area on the blades. Also, the pitch on the OEM fan blades is much greater.
Installed now is a 17" 6 blade Derale flex fan. Nice quality, no sharp edges, but doesn't move much air and looks a little too small. Not much surface area on the blades.
I can honestly tell you an 18" fan will not fit inside my shroud with enough clearance. Still want to try a clutch fan. So far I found one Hayden heavy duty series thermal type clutch that might fit correctly, p/n 2747. I am going to order it and try. Hayden does have a standard duty thermal type clutch that fits. But, from my experience, standard duty thermal or non thermal clutches don't work that well.
If the heavy duty clutch doesn't fit, I am thinking of either looking for a good original 17.5" flex fan. Or carefully trimming 1/4" off each blade of a new 18" 6 blade Derale flex fan. They certainly don't look to be accurately balanced. I think small trimming won't hurt it any. If the heavy duty clutch fits I'll try trimming 1/4" off each blade of an 18" 6 blade Derale fan for a clutch.
Update, still trying to find a suitable fan for a clutch setup. So far the best candidate I found is an OEM 7 blade 17.5" diameter fan for a 1968 Cougar or Shelby GT 350. It is the correct diameter and there are a couple on EBay. I like it but shipping is rather high so I haven't purchased anything yet. The aftermarket fans for a clutch don't look like they will move much air compared to an OEM fan.
I ran into and old friend at a car show this weekend. He is running a 408 stroked Cleveland. Says he has no problems with getting hot. 24 inch radiator and a factory, I think its a 6 blade fan. He is a retired Lincoln Mercury parts manager. I am sure the parts were acquired nos. stuff. The number on the blade is C5AE-B if you cant see it.
I like the clutch idea. I'll wait to see how you make out. Not sure about trimming the blade for a .25 or .5 inch though.
I may even go to the bone yard and take a tape measure. Check the sizing on some later models ford trucks. A lot of them ran a thermostatic clutch/fan set up. If I can pick something up for just a few dollar's even just to size. Maybe even get lucky and find something that fits. Then get new parts. Thanks, Cheers J
![[-]](https://mach1club.com/images/collapse.png "[-]")
