I am working on my 55 F100, with 460. Using a mid 70's F150 radiator (with Auto tranny cooler too)..
But where I placed the engine there is no room for a typical engine mounted, or electric puller fan. (1 inch clearance water pump to radator)..
SO.. gotta go with a pusher.. So I have this 16in, curved blade fan in pusher mode... and I need to add an A/C condensor too.
seems to me that the fan will blow on the condensor (without a shroud) and the air will flow away from the radiator, without going thru. General recommendation I've seen is 1 inch spacing between condensor and radiator.
Oh, my hotrod buddies suggest an additional tranny cooler too.. so BOTH of these would be in front of the radiator..I've found a couple of thses that are narrow (3-4 inches) and radiator wide (23 inches). and can get an a/c condensor to fill this space too, at 22x14 or 20x13.
the fin area is 24x19.. using a front mounted shroud would knock that down to a 16 circle.. 456 square inches(fin) vs 200 square inches (fan).
SO, I was thinking of using a design that is used on puller shrouds. Wind deflected vents.. slots in the shroud with rubber flaps against them that are closed in low speed with the fan on, and are pushed open when driving faster..
If I placed the shroud skin 1 in away from the condensor, then I would have room for 3/4-7/8 in flaps to open under wind pressure.
If I wanted to add 100sq inches of airflow, I would need approx 130 inches of 3/4 slots in the shroud.
I run a 351C with a 16-inch puller. No AC yet. I use a remote tranny cooler and a remote oil cooler.
If your radiator already has a tranny cooler, I would not add another one. The tranny cooler cuts down the area available to cool water. Adding another tranny cooler just sucks more cooling capacity away from the radiator for no particularly good reason. If the tranny runs THAT hot, get it serviced. The factory tranny cooler should be sufficient.
I started running a shroud under the 16 inch and found that I had MUCH superior cooling without it. I would recommend against a shroud. The air won't deflect away from the radiator. I mounted my fan directly to the radiator. Flappers on a puller shroud do increase the cooling area when moving at a higher speed, but still reduce the overall area (like your calcs showed). That's why mine mounted directly to the radiator worked so much better at freeway speeds.
I would suggest a high cfm fan in the 2400-3000 cfm range just to be safe. Maybe your curved blade is already in that range. In any event, the radiator volume and flow rate has more effect on cooling than the fan. My fan is only 1600 cfm. It works great, but I would just like to suck the temp down quicker.
Your radiator should be a four-row style at least. Make sure you run a thermostat or, at least a restrictor plate where the thermostat goes in order to slow the flow down enough to pick up heat in the engine and radiate it out thru the radiator. A big mistake people make is having too fast a flow thru the system. Some folks also run a restrictor in the lower radiator hose to slow the flow down. A 5/8 dia hole in the restrictor is suggested.
I use a relay switch to bring the fan on at temp and shut it off when cool. Hayden p/n 3652 (Pep Boys - $36). Works great. I also installed a dash switch to bypass the relay (provide a ground to it) to turn the fan on whever I want to. Or, you could add that extra ground off of the AC clutch ground so that the fan comes on when the AC comes on. OR, you could run the fan all the time the engine is running (thru the accessory breaker/fuse) like some do. Up to you.
Last edited by Randy Jack; 08-02-2005 at 03:43 PM.
Sam, I agree about the fan blowing thru the condenser. I tried this on a street rod, only to discover what you fear. What I did was mount a remote condenser with shrouded fan under the car. Worked well, allowed the electric fan on the front to work. I have done the same on another street rod with also good results. I don't know if your idea on slotted front shroud would work, but I do know that if there is anyway to move the radiator forward and mount a shrouded electric puller you would be far better off. I am pretty sure that my Cooling Components Inc. set up is 2 1/2 " deep.
Another interesting idea came up yesterday, talking to the guy who built my custom power steering hose.. use a shroud for the fan size only, off center, and put the a/c condenser under that shroud.. so it would be 18x18.. and then put a small puller on the back (I have room for a single 9inch I think in one corner)..