Balancing a set of connecting rods is the process of modifying the rods so that they all weigh the same. Balancing and or lightening a motor's internal components is a time-honored technique in the building of performance engines. An engine's internal components include parts like the crankshaft, pistons and connecting rods. The more balanced and light these components are, the better your engine will perform, with smoother revving and more horsepower.
Things You'll Need
- Die grinder or dremel
- Grinding stone
- Sanding cones
- Small scale
Clean the connecting rods with degreaser. You can also have them hot-tanked (chemically cleaned) by a machine shop, which is a much more effective way to get them completely clean.
Examine the length of the rods. You should see a casting seam running down the side of the rod. Use a dremel to grind this seam off of all of the rods. Do not gouge the rod or remove any material besides the casting seam itself.
Smooth out the grinding marks with a round sanding tool on a dremel or a high-speed die grinder. The point here is not to completely polish the rod, but to eliminate the grinding marks and smooth out the metal.
Place the rods on a balancing fixture (see Resources) to weigh both ends of the rod. A balancing fixture is a device that holds one end of the rod free, and places the other end on the scale so that the weight of each end of the rod can be determined.
Measure the weight of both ends of the connecting rods on the scale. You will be lightening the heaviest rods down to the weight of the lightest rods with the die grinder or dremel.
Grind off excess material from the both ends of the rod, using a die grinder or dremel, until they all weigh the same as the lightest rod in the set. Stop and measure frequently to avoid removing excess material. To avoid weakening the rod, do not grind off material in the middle of the rod or material that is very close to where the rod attaches to the crankshaft or to the piston. Instead, remove material from the outer ends of the rods. There should be extra material in these areas that can be removed.
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