Unless shrouded, 3.5 is probably too far Randy. Although it'll probably work. Stopped in summer heat idling might be a problem as it pulls hot air back around from the engine compartment.
1.5" or even closer with the heavy stock blade would be better.
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65 Laurentian post, 67 Grande Parisienne 4 door HT.
Sorry Randy, you have a shroud! Of Course, a 69, doh!
I think the optimum placement puts the fan engine side slightly outside the shroud. Like just 1/4 of the blade end on. I heard it described as being just outside, allows the hot air to be directed somewhat 90 degrees to the front of the block. Not all right back at it backing up the flow. A engine with a ton of driven accessories clogging the path probably should follow this, simple setups like we have are fine.
So you are probably fine where it is.
I've had very good luck and cooling with this placement on both the 350 and 496.
Ive always heard blades should be half in half out of the shroud for best cooling.
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63 Parisienne sport coupe (The Big GTO), black, maroon interior, 409 4 speed; former owner of a 59 El Camino, 63 Corvette SWC, 62 Chev Bel Air SC. 1963- Pontiac top selling car in Canada
Mahone Bay, NS Still not old enough to need an automatic
cdnpont is the most correct. The blade front (with the bolts) if you took a straight edge it should be toward engine maybe 1/2". So that the twisted end of the blade is just inside the shroud. That is the MOST efficient, moves the most air. The efficiency is in moving the largest amount of air. In/out too far ruins it
PS.. There is some scientific formula for this, beyond my mindset LOL
Yep, just a Don reports, the internet tells us all that 1/2 way in is best...
I think as long as it isn't completely shrouded it should work.
I visualize in my mind... if the fan was efficient, the end gap small, and it could pull more air than the rad would allow through at higher RPM, then you'd get some kind of pressure drop on both sides of the blade, basically a stall. Picture a wing losing flow.
Having some blade outside allows some free air moving down onto and out of the blade keeping some negative pressure to the outside. But this is just all in my mind mind you...
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65 Laurentian post, 67 Grande Parisienne 4 door HT.
All my old cars with stock fans and shrouds lined up half in half out of the shroud. But Im a 59-63 guy and they all had shrouds.
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63 Parisienne sport coupe (The Big GTO), black, maroon interior, 409 4 speed; former owner of a 59 El Camino, 63 Corvette SWC, 62 Chev Bel Air SC. 1963- Pontiac top selling car in Canada
Mahone Bay, NS Still not old enough to need an automatic
