Good old number 29's Activity
Good old number 29 added a topic in Technical tasksCarb heat boxWithout starting a debate about engines that don’t need it, here is a cheap and effective way to rig up carb heat. It requires only hand tools to build. Including prep time and layout, it took me six hours to make. I had the sheet metal and the heat muff already, so my only cost was $12 for the control cable. Estimated cost for all the materials is less than $100.
Here is the finished product:
The cable actuates a flapper door to select one of two outlets. One outlet goes to the carb, the other to cabin heat. The inlet air comes from the heat muff on the muffler. The diverter box could also be used select defrost or floor heat, or hot or cold air.
Tools and Materials:
12” x 18” of .025” 2024 T3 aluminum
1/8” aluminum pop rivets, 1/8” & 1/4” lengths
Heat muff for the exhaust
5 feet of 1-1/2 inch diameter high temp hose
16 penny galvanized nail
2”x 3-1/4” 20 gauge galvanized steel
(2) 1/2” #6 machine screws with lock nuts
(5) 1-3/4” hose clamps
1-1/2” hole saw
Flat metal file
1” diameter pipe, tubing, or dowel
NAPA choke cable
Steel welding wire
I will attach more pics for clarification of these confusing directions. It is not as hard as I make it sound. Currently only able to load one pic. I’ll load the rest when I’m able.
Cut four pieces of T3 at 5-1/8” x 1-1/2. Mark at 4-9/16”. Bend each piece around the 1” pipe to round it into a 1-1/2” long x 1-1/2” o.d. tube. Use the hand seamer to finish the radius on the ends. Overlap the end to the mark that you made. Use a hose clamp in the middle to hold it at the right diameter, drill and install two rivets in the seam. It should fit tightly in a 1-1/2 hole, and the heater hose should slide on tight. Make parallel cuts 1/2” apart, 1/2” long, up from one end. This 1/2” will bend out to make a tab which will be used to rivet it to the body of the diverter box. Make three tabs, equally spaced, on one end of each tube. Bend them up very carefully, using the pliers. Spread the bend out a bit. The tabs will break right off if you just pinch and bend.
Cut a flange out of T3 for the air filter, as seen in the picture. It should be about 8” square. I angled the top corners down from the rivets. Snip 1/8” off the corners at a 45°, and round them with the file. Do that on all the sharp corners. Brake it 90° at 2-1/2 inches, clamped between two pieces of wood in the vise. Use the hole saw to cut a hole in the center of the short side. Attach one of the 1-1/2 hose fittings by sliding the short end into the hole, tight to the three tabs, then drill and rivet in place. Mark 2-1/2” up from the 90, drill and rivet the plate to the back of the air filter with four rivets, with the bottom of the air filter at the mark, leaving 2-1/2” gap to the 90° flange.
Mark out the diverter box. One piece will make the bottom and sides. A second piece will be the top. I’ll post more pics to make this part clearer. The box is two inches deep. One end of the box is two inches wide. It is four inches long. The other end is four inches wide. Take a 9” square of T3. Measure 2-1/2 inches from the edge, and mark the shape of the box. Mark 2-1/2” out from both sides and the ends, parallel to the sides of the box. The sides of the ends should be 1/2” longer than the bottom, to wrap around the sides. That is, the bottom and sides are one piece, and it all folds up, with the ends wrapping over the sides to be riveted together. Mark 1/2” from the top of each side. Brake the sides up 90° from the bottom of the box. Brake the 1/2” at the top 90° down, to the inside, parallel to to bottom. This is the flange to which the top will mount. Brake the 1/2” ends around the sides, drill, and rivet in place. Mark center on the short, 2” square end, and put the hole saw there. On the opposite end, mark and cut two holes with the hole saw, 1” on center from each side. Rivet one of the hose adapters in each of the three holes.
At the long end of the box, top and bottom, centered, and tight to the end, drill a hole to fit the 16D galvanized nail through. One hole will be on the bottom, and one will be on the flange at the top. This is for the flapper hinge. Cut 2-5/8” x 2” from the 20 ga. galvanized sheet. Radius the corners. It should fit tightly to one side of the nail. Trim the tight spots so it fits easily when it pivots to either side, without much gap. Allow the head of the nail to have some end play so it doesn’t bind. Tack weld the flapper securely to the nail. I used L56 .025”. Test to make sure it has free and full movement.
Cut the top of the box. You could trace the bottom, or mark it 2-4x4. Cut it 1/8” small, and the edge won’t stick out. Cut a notch in the long end to clear the nail. Nip and file to clean up and smooth the edges. Making sure the box is straight, not warped, drill for two rivets on each side, through the top, into the flange beneath it, placed so they do not interfere with the movement of the flapper, and rivet it in place.
Cut 3/4 x 1-1/2 from the remaining scrap of galvanized sheet. Use the hand seamer to bend it into a U shape, the short way, so you have a 1-1/2” long stick of 1/4” channel. Drill a hole in one end to fit over the nail. Drill one or more holes in the other end to attach the cable. Fit this actuator lever over the nail, in line with the flapper, leaving 1/8”-3/16” space between the top of the box and the lever, and tack weld it to the nail. Cut off the end of the nail above the lever, using the hack saw.
Cut 1-1/2” square and another piece, 1/2 x 3/4”, from the T3. Make a 1/2” cut, 1/2” in from one side. Brake it 90° down along that line, then carefully bend the cut end out about 60°. This is the cable mount. Bend the small piece slightly to fit the cable housing, clamping over top of it. Again, using caution to avoid interference with the flapper, rivet the cable mount to the base with three rivets; two on top and one through the tab on the side. It should be placed so the cable is at the proper place and angle to push and pull the actuator lever through its full range of motion. Position the top clamp, drill, and attach with the two #6 machine screws.
Attach hose from heat muff to box inlet. Attach hoses from the two outlets, one to the carb heat, the other to cabin heat. Mount the air cleaner, mount the box (not blocking flapper travel with any hardware), mount the cable.
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