How To Pour Connecting Rod Babbitt Bearings

new pot

The only special equipment needed to pour babbitt bearings are the cast iron melting pot and the ladle shown here. The bearing scraper is homemade from a small three-cornered file, ground to sharp edges on two sides. The pine stick is used as a temperature indicator of the babbitt.

Photo by Bud Motry

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Worn out or missing connecting rod bearings are frequently a problem with old engines. Sometimes it is possible to locate bearings to fit, but it is costly and takes a long time.

With a minimum of equipment, a cast iron pot and a ladle, that may be procured at a flea market for $15.00 or $20.00, you may pour your own bearings.

It takes a little ingenuity to make a fixture to hold your old connecting rod, but the fixture can be made from wood. Note the crude example, though entirely effective, in the photo. Babbitt is available from old engine suppliers and some local auto parts stores. It costs about $4.00 a pound, which is sufficient for most bearings. The wood fixture you see here was made from a piece of 2' X 4', about 20' long, and a piece of 1' X 4', about 6' long.

The bearing for this rod needed a flange on both sides of the bearing. It is necessary to measure the outside diameter of the rod casting. Drill a hole, slightly smaller than this diameter near one end of the 2' X 4' block. It should only be drilled about 1/8' deep, using a hole saw. The inside of this hole must be cleaned out with a wood chisel. The connecting rod journal diameter has been measured, assuming it is 1.250' in diameter, locate a shaft of this diameter, you will need a short piece, perhaps six inches long. Drill a hole, this size precisely, in the center of the large hole drilled in the 2' X 4' block. It need be only about one inch deep. This hole will support the dummy shaft. Next, a hole is drilled in the 1' X 4' block the same diameter as the large hole in the 2' X 4' block. Drill all the way through this piece. This piece will be placed over the connecting rod, to hold it in place, and form the flange on the other side of the bearing.

The connecting rod is now checked for shims. I usually add a sixteenth of an inch shims or more, between the cap and rod of the connecting rod. The pieces are smoothed with a file, assembled, bolted in place, and any openings are plugged with wood. The rod is now placed on the block, checked for centering over the shaft and aligned with the large opening. I usually drive nails on both sides to hold it in position. The wrist pin end of the rod is then checked to see if it is level with the big end of the rod. It is usually necessary to shim under the rod to make it level. (Note the piece of wood in the photo.)

The 1' X 4' piece of wood is then placed over the big end of the rod and centered. This piece is then attached with two wood screws to the 2' X 4' block to hold the rod in position. Check the fixture again for perfect alignment. It is advisable to use a bevel protractor. (Note the use in the photo.)

The next step is to heat the babbitt over a gas burner. It takes a lot of heat to melt the babbitt. It should be heated hot enough, according to the old books, so that a piece of pine stick will smoke when removed from the molten metal.

After the metal is ready to pour, the connecting rod casting and the shaft should be heated with a torch. It may char the wood, but no harm is done. I heat the casting both on the inside and outside to the approximate temperature of melting solder, about 450° Fahrenheit. At this time wood plugs must be in place, or inserted, in any threaded openings in the rod.

Skim the slag off the top of the molten metal and discard it. Fill the hot ladle with clean babbitt and carefully pour it in the rod opening. Slight leakage will quickly seal and additional metal may be poured. It will blend with the previous pour.

After the metal has cooled twenty or thirty minutes remove the wood fixture. The shaft may be placed in a vise and twisted off, but if an arbor press or hydraulic press is available it is easier to press the shaft from the bearing. Excess material on the side of the bearing may be sawed off with a hacksaw or finished with a file and a scraper. It will also be necessary to cut the bearing at the shim edge, between the cap and the rod in order to remove the cap. Depending on the accuracy of the job, there may be very little fitting necessary. However, in some cases it may be advisable to use a reamer to finish the bearing to size. If the shaft used was a little smaller than the journal size it can easily be taken care of by using a reamer on the bearing.

After checking the alignment of the rod to the center bore of the cylinder and finding you have miscalculated, the rod may be heated and the bearing poured back in the melting pot and you can start all over again.