[JohnIL]

New Thermostat Housing
A couple of updates ago, I mentioned that I installed a new thermostat. That installation exposed a weakness in the thermostat housing/water neck. The old housing was cast aluminum and had obviously been on the engine for a long while. The sealing surface was no longer flat and had a bit of corrosion. My attempts at resealing the housing were unsuccessful. The solution was easy. I tossed the old housing in the trash and installed a shiny new chrome housing that utilizes an o-ring seal. Problem solved.

Fan Shroud
I mentioned in my last update that ordered a Speedway Motors DIY aluminum fan shroud kit. I believe the kit is actually made by Northern Radiator. Installing this kit turned out to be a much bigger project than I expected. I knew there would be some assembly and fabrication involved, but I severely underestimated what it would take to make this shroud work with the C10. If you are in the market for a custom fan shroud, buckle up and read on. This is going to be a long one...

I chose the Speedway Motors kit because of its universality. Originally, I wanted to use a factory-style fan shroud, but there isn't much factory-style equipment left under the hood. The engine isn't factory and the radiator isn't factory. So, a universal shroud was really the only choice. The radiator in the truck is a bit of a mystery. The radiator core appears to match the dimensions of the factory V8 radiator, but whoever installed it had to notch both frame rails to make room for the width of the bottom tank. I suspect the radiator is a replacement radiator for a later '67-'72 C10. Also, I'm missing the side baffle plates that the original fan shroud would have mounted to. I suspect they were removed when the wider radiator was installed. That left pretty much nothing for the new shroud to mount to. Speedway Motors sells these kits in several sizes. I chose the size that was closest to the size of the radiator. It fits the height of the radiator well, but it is about 4" narrower than the radiator core (about 6" narrower than the radiator tanks). The kit comes with two primary pieces, a large rectangular pan and an extension ring.

I began the installation by fabricating new side baffles. I used some 20ga sheet steel that I had on hand. Heavier steel would have been better, but more difficult to bend without a brake (maybe someday). I mounted the baffles to the core support using the factory mounting holes. I extended the baffles around the front of the radiator about 4" on each side. I used these "wings" as mounting points for the new shroud. To help stabilize the thin metal baffles, I welded ribs, made of bar stock, to the inside near the top and bottom.

With the baffles in place, I removed the cooling fan and temporarily mounted the rectangular pan. I marked the center point of the water pump pulley on the shroud. Then, I dismounted the shroud and cut out a circle large enough to clear the fan blades. The challenge was that the fan blades were larger than surface of the pan. The pan is about 18 tall and about 22" wide. The last two inches of each side are angled (flared) toward the radiator. That gives you an approximately 18" x 18" face to work with. In order to accommodate the 19" diameter fan blades, the circular cutout (about 20" diameter) extended beyond all four sides of the pan. It was just as ugly as you can imagine. I prettied it up later on.

The next step was to add the extension ring to the face of the pan. The pan is 2 5/8" deep. The 3" The extension ring is intended to be mounted to the face of the pan, extending the depth of the shroud to 5 5/8" inches. That was more depth than I needed. So, I recessed the ring about 3/4" into the surface of the pan. This served three purposes. One, it made the shroud shallower. Two, the structure of the pan helped to keep the extension ring round and significantly stiffened the ring. Three, it helped to visually "integrate" the two pieces together. Instead of looking like two pieces cobbled together, they now look like they were meant to fit together.

Once the two pieces were joined, I removed the baffles, gave them a coat of flat black paint, and reassembled the whole thing in the engine bay.

The part that I didn't expect was the fiddling time involved. It took A LOT of test fitting, cutting, bending, adjusting, and cursing to get everything to work together. I lost track of how many times I removed and reinstalled the baffles, the pan, the extension ring, and the fan. All told, I have about 30 (not a typo) hours of garage time into this silly fan shroud.

On the plus side, I like the way it turned out and it seems to do its job. I took the truck for a test drive. Out on the open road, the temperature never climbed over 170 degrees. Around town, it never climbed over 180 degrees, even sitting still in traffic. I will keep an eye on the temperature on the next 90+ degree day to verify the results.

What's Next?
I need to get the truck ready to go to the exhaust shop, hopefully in the next couple of weeks.

I have a fuel pressure regulator that needs to be installed. The fuel pressure provided by the mechanical fuel pump is just on the high side of the recommended pressure for the Edelbrock carburetor. The regulator will keep me in the safe zone and prevent the needle valve from getting overpowered.

The backup lights can wait for a rainy day. Besides, I'm still building up the courage to drill those giant holes in the back of the quarter panels anyway.