Oil Cooler Butterfly Valve

Time: 8 Hours

Now that I have 20+ hours on the engine it is apparent that I will need better control of my oil temps. Even with a good portion covered I was only able to get the temperature up to 185°. The manufacture of the oil cooler mount/shroud, www.showplanes.com has a butterfly valve kit now that will allow you to control how much air you want to go to the oil cooler from 100% to 5% based on their website. So I ordered that kit form them as well as a cable and knob from McFarlane Aviation.

I needed to remove the cooler shroud so I would have access to the baffle. The first step is to mount the outboard pivot block that the valve rod rotates in. I measured half way based on the baffle opening and marked where I needed to drill for the screws. Once one was drilled I could use the other hole as a drill guide.

Once the outboard block was screwed in place I could drill the 3/8” hole for the rod using the block as a drill guide.

I removed the outboard block and opened the 3/8” hole to a 9/16” hole for clearance.

That hole got cleaned up and I installed the block again and slid the rod through the block and hole in the baffle. This allows me to level the rod and place the inboard pivot block so I could drill its screw holes.

Once the rod and pivot blocks were in place I could start on the plate that will act as the shutter. The one that came with the kit wasn’t perfect for my opening so I sue it as a template for one I made out of .032 sheet I had. I used the screw holes as a starting point and made extra measurements to get the size I wanted. I decided to do a double bend of sorts to get the lower half to close as much of the opening as possible.

After I had the shape finalized I added a small piece of aluminum tube that they supplied and a couple of washers on either side of the outboard baffle wall where the rod goes through. These keep the valve centered in the opening and keep it from moving sideways.

The way the valve opens and rotates inward into the fiberglass shroud causes a problem with the inboard lower edge of the sheet hitting the shroud. So rather than trim the cover and loss some of it effectiveness in blocking airflow I decided to modify the shroud a little. I measured and trimmed the shroud so that it wouldn’t interfere with the valve. I then created a mold out of styrofoam covered in packing tape and laid up a couple layers of fiberglass to create a bump out. This will hopefully provide enough clearance for the valve to open freely.

While the fiberglass cured I started the work on where to put the cable and pull knob for the control of the shutter. I decided to put it between the cabin heat and the alternate air pull knobs.

Once I decided that location I worked on the route where the cable would run. The first thing was to work on the firewall pass through.

Once that was finished I ran the cable through the gear tower placing the washer and nut on as I thread it through. Then I used adel clamps to secure the cable as I ran it across the engine mount to the oil cooler. Once I had the cable secured I could measure and cut it to its final size. I adjusted the length so that I had the proper through from open to closed on the valve.

I adjusted the cockpit end so that the knob was lined up correctly and tighten the not to hold it securely. I bought the cable and knob from Mcfarlane Aviation and had the custom knob say “Oil Shutter, Pull On” in the clear anodized.

With the cable all run and it’s function tested all I needed to do was prime and paint the valve, finish the touch up work on the shroud for paint.

I cleaned up the valve and painted it with the same silver as the baffles. I finished up sanding the shroud and primed/painted it as well. Once the paint was dry I started putting all the parts back together. I cut a new piece of the rubber seal that goes on the lip of the shroud to seal it to the baffle as it needed to be slightly longer due to the change in the side I made to clear the valve as it opened.

Now all that’s left is to close everything up and test it in the cold Chicago weather!

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