daveid said:
so would a stainless steel 7 blade 18inch flex a light fan work? My only question on the mechanical fan is, If my heat problem comes when im idling, isnt that not going to work as well since my rpms will be the lowest then and therefore the fan will be spinning at the slowest it can?
thanks again,
david
Above 30/35 MPH, you don't need a fan at all, so it's all about low rpm, low speed cooling. This is where an OEM-type system works best. It's about the diameter and pitch of the fan blades and a good shroud that fits close to the radiator core and completes a 360-degree circle around the fan blades, with the fan blades half-in and half-out of the shroud opening. Also, the fan blades need to be close-fitting to the shroud hole on the diameter. An 18-inch fan with a 19-20 inch shroud hole will work just fine. The shroud hole needs to be large enough so that the blades will not contact the shroud as the motor rocks laterally on the motor mounts, but not so big that the blades cannot pull a good vacuum between the blades and the radiator core.
It sounds like you're hung up on a flex fan. You don't need a flex fan with a fan clutch. You need a solid steel OEM 18-inch, 7-blade fan with a thermostatically-controlled fan clutch mounted on the front of the fan blades. (actually, the fan clutch mounts to the water pump and the fan mounts to the fan clutch). A good fan will have a pitch of around 2 1/4 to 2 1/2 inches. Lay the fan down flat on the floor and measure from the floor to the edge of any fan blade to find the pitch. I used a fan from an Olds diesel once when I was skeptical about being able to cool a high-compression motor in a tight engine bay. The pitch was 3 inches.
Also be cautious when choosing a fan for a conventional vee-belt drive application that turns the water pump in a clockwise direction as you're looking at the front of the motor. If you use a fan from a late-model application that uses a serpentine belt system and turns the water pump counter-clockwise, you'll be blowing air toward the front of the radiator. The pitch is reversed on those fans. You cannot turn a fan around to blow the other way, it won't work. A fan blade will only blow air one way, no matter which way you mount it, correctly or backwards. You must use the correct fan with the correct direction of pitch for the application you're building to. If you're using a conventional vee belt water pump that turns clockwise, then use a fan that was designed to work with a clockwise water pump. If you're using a serpentine belt water pump that turns counter-clockwise, then use a fan that was designed to work with a counter-clockwise water pump.
While I'm on this subject of fans and fan blades, I want to bulletproof it for everyone. I'm not very good at describing this without an illustration, but try to follow along.
You know how you hold a tire/wheel when you're mounting it onto an axle or hub? Hold the fan the same way and then move it down to the floor, with your head directly above the fan so that you're looking down on a blade. If the blade orientation is northwest/southeast, it's a conventional vee belt drive fan that is meant to rotate clockwise as you're looking at the front of the motor. If the blade orientation is southwest/northeast, it's a serpentine drive system fan that is meant to rotate counter-clockwise as you're looking at the front of the motor. Further, any fan can be mounted frontwards or backwards and will still work the same way, however one way it will be efficient and the other way it will be inefficient. Any fan blade needs to have the concave, hollowed-out side facing the motor, with the convex, rounded-out side (like a fat man's belly) facing the radiator.
And yes at idle it is hooked up.. Not turning as slow as a reg fan...Tech and Vince if this p**** y'all off I'm sorry.. But this forum is about info.. Good and bad.. But just because yall don't like them don't make it wrong to run one..It can be done, and is still being done...Like I said.. I don't want anyone mad.. But I do Know first hand, That it does work well,, And I have ran them On some very hot big block's, and 100* + Days..The size of your rad is most important ...Good luck with what every you do..
