A few days ago, a fellow 'bolter posted seeking info about six blade fans for 235/261's. I responded with the following excerpted from two posts-- ______________________________________________
TF trucks 3/4 ton and larger with sixes had a heavy duty cooling option that included a larger radiator, a fan shroud and a 20" five blade fan with eccentric blades. I think it might have been stock on some of the larger trucks, but I am not sure.
The heavy radiators are about 1/2" thicker and 2" wider, but fit into the same mounting holes on the core support as the regular radiator. If you look at a standard radiator on a TF pickup, the mounting brackets on the sides are angled at about 45 degrees to fit the mounting holes on the core support. The ones on the heavy duty radiator are not angled to accommodate the wider core and tanks. The heavy duty radiator also has mounting clips for the fan shroud. The larger radiator was not offered on 1/2 ton trucks, but it does fit. US Radiator makes replacements either with standard size tubes or smaller tubes for even greater capacity. They are available with or without a transmission oil cooler.
The fan shrouds for the sixes are very hard to find, kinda like hen's teeth. Repops and originals can be found for the V8's, but not the sixes.
The five blade fans are hard to find, but they are out there. I have found two or three over the years when searching boneyards. All of the ones that I have found have been on big trucks. I have never found one on a pickup. ______________________________________
I have a friend who is an excellent fabricator who specializes in making aluminum fan shrouds for hot rods. He has developed tools and techniques such as rolling the edge to allow the exposed fan tips to catch and channel more air just for making fan shrouds. He makes them for high end projects on the West Coast including doing the custom ones for SoCal Speed Shop.
A couple months ago, he was in my garage looking for ideas for a '56 big window that he wants to begin. He saw my factory shroud and scratched his head because he had never seen one before. I explained the high capacity option discussed in my above post. I also mentioned that there isn't one available for sixes with a standard radiator and that I occasionally see requests for them on Stovebolt, especially when someone is adding AC.
He took that as a challenge. Using my shroud as a guide and a spare standard radiator that I had laying around, he fabbed a shroud to fit the standard radiator and either the stock four blade 20" fan or the optional five blade 20" fan on either a 235 or 261.
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Here are pictures of the prototype shroud that I'm about to install. The brackets will attach using the radiator mounting bolts. Since the core support is angled forward, the radiator brackets lean the radiator back to keep it vertical. Because of that, the three brackets on each side of the shroud are all different to match the angle of the radiator brackets. Making those brackets has been the tricky part. Note the bead-rolled edge where the fan tips are exposed. That increases the efficiency of the blade/fan combination. The shroud is designed to leave 1/2 of the fan tips exposed.
I'll add pix of the installed shroud once I get it in. To install, the radiator needs to come out, then the fan shroud is placed over the fan and rests on the water pump shaft to keep it out of the way, then the radiator goes back in, then the shroud gets attached to the radiator. There is not enough room to simply slide the shroud in place without removing the radiator.
