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Bearings & Rods

Now secure a sliding cot, a quantity of clean rags, hammer, extension light, pair of side-cutting pliers, and an assortment of end and socket wrenches to fit the bearings and nuts that are to be worked on.
When all the tools have been gathered and the car placed in the position as indicated the mechanic is ready for the job.

Checking Connecting-Rod Trueness
After preparing for the job as outlined above, the oil is drained, the pan dropped, and the loose rods marked, both on the cap and shank for identification.
This is done before removing the rods, it being important to insure that the rod be reinstalled in the same relative position.
The marks made on the rod should face either toward or away from the camshaft, and this fact should be remembered by the mechanic as his guide when reinstalling.
Before the rod assembly is removed, however, the mechanic should turn the crankshaft slowly while seated below and watch the action of the top of each connecting rod during a full revolution of the shaft.
If the top of any rod moves back and forth between the piston bosses more than 1/16", it indicates a bent connecting rod or a piston pin that is not parallel with the crankpin. Each of the four, six, or eight connecting rods should be observed in this manner and correction made either by straightening the rod, installing new pistons, or reconditioning the crankshaft before the job is sent out.
With the rod assemblies removed, the mechanic can now proceed to check the condition of the crank-pins, which will be accomplished either with a special outside reading dial gauge or with a pair of outside mikes.
Fig. 16A
Fig. 16. Checking the crankpin with a precision tool is first step in bearing maintenance. The micrometer (above) and an outside dial gauge (Fig. 16A) are the only instruments that will accurately test connecting-rod crankpin for circularity.
Fig. 16A. Ames crankshaft gauge. Will show if crankshaft or crankpins are out of round, and will measure exact diameters.

This check on the crankpins is to determine if they are tapered, out of round, or roughened.
The micrometer should be applied to at least three points along the length of the crankpin to check for taper and at least four points around the pin to check for roundness or circularity.
When applying the micrometer to different points of the circumference in the test for roundness, it is also well meanwhile to move the micrometer from one end of the pin or journal to the other, not, how-ever, with the idea of testing for both roundness andtaper in one operation. These two tests should be made separately, as indicated at Fig. 16.
If the outside type of dial gunge, as illustrated in Fig. 16A, is used, it will give a continuous reading and will indicate taper and out of round while being moved around the crankpin.
If either the special outside reading dial gauge or the micrometer shows that any of the pins are more than 003" out of round, or if the pin surface is scored or badly cut, it will be necessary to recondition before attempting to readjust or refit the rod bearings. Crankpins should have a flawlessly smooth finish.
The best job of reconditioning will be accomplished by mounting the shaft in a crankshaft grinding machine, but where it is not advisable to remove the shaft, the mechanic can avail himself of the several makes of retruing tools, practically all of which can be used without removing the shaft from the engine.
Where the shaft is roughened slightly and not out of round beyond .001", it is possible to bring it back to standard surface by using a lapping tool, such as the one shown at Fig. 8.
Another method often used by mechanics consists in utilizing a strip of emery cloth wrapped around the crankpin and rotated by a shoe string of cloth or leather looped once around it. The emery cloth should be used dry for the roughing work and with oil to impart a final smooth finish.
The lapping tool also can be used effectively to finish up the job that was started with the retruing cutter.
In other words, the lapping tool or the emery cloth methods are excellent for imparting the final smoothness after taper and out-of-roundness have been removed with the retruing tool.
When the lapping tool is used, abrasive action is secured by turning the crankshaft while the tool is clamped over the journal from below.
If either emery cloth or the lapping tool with compound is used, the pin and adjacent parts of the shaft should be carefully washed after the reconditioning has been accomplished.

Removable Type Bearings
Assuming now that the crankpins have been inspected and reconditioned and meet the standards previously mentioned, the mechanic can then proceed to check the condition of the connecting rod, bearing surfaces, and cap.
On the majority of engines this inspection can be made in a short time, as there are few parts that can become deranged in the cast-in type of rod bearings as now used.
On some constructions it will be found that shims are used, while in others the bearing is of the style known as the full-round shimless type.
Regardless of the construction, the first check is to inspect the condition of the split edges between the rod and cap forgings as shown at Fig. 17.
Fig. 17. The cap and rod forgings at split faces should be flat and true.

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Carburetor Manuals: Bearings & Connecting Rods