Dodge Colt/Challenger/Conquest/Vista 1971-1989 Repair Guide

Crankshaft and Main Bearings



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Fig. Fig. 1 A dial gauge may be used to check crankshaft end-play

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Fig. Fig. 2 Carefully pry the shaft back and forth while reading the dial gauge for play

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Fig. Fig. 3 A dial gauge may also be used to check crankshaft run-out

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Fig. Fig. 4 Turn the crankshaft slowly by hand while checking the gauge

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Fig. Fig. 5 Mounting a dial gauge to read crankshaft run-out

  1. With the engine out of the car, remove the intake manifold, cylinder head, front cover, timing gears and/or chain, oil pan, oil pump and flywheel.
  3. Remove the piston and rod assemblies. Remove the main bearing caps after marking them for position and direction.
  5. Remove the crankshaft, bearing inserts and a rear main oil seal. Clean the engine block and cap bearing saddles. Clean the crankshaft and inspect for wear. Check the bearing journals with a micrometer for out-of-round condition and to determine what size rod and main bearing inserts to install.

To install:

  1. Install the main bearing upper inserts and rear main oil seal half into the engine block.
  3. Lubricate the bearing inserts and the crankshaft journals. Slowly and carefully lower the crankshaft into position.
  5. Install the bearing inserts and rear main seal into the bearing caps, install the caps working from the middle out. Torque cap bolts to specifications in stages, rotate the crankshaft after each torque stage.
  7. Remove the bearing caps, one at a time and check the oil clearance with Plastigage. Reinstall if clearance is within specifications. Check the crankshaft end-play, if within specifications install connecting rod and piston assemblies with new rod bearing inserts. Check connecting rod bearing oil clearance and rod side play, if correct, assemble the rest of the engine.


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Fig. Fig. 6 Apply a strip of gauging material to the bearing journal, then install and torque the cap

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Fig. Fig. 7 After the cap is removed again, use the scale supplied with the gauge material to check clearances

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Fig. Fig. 8 The notch on the the side of the bearing cap matches the groove on the bearing insert

Remove the cap from the bearing to be checked. Using a clean, dry rag, thoroughly clean all of the oil from the crankshaft journal and bearing insert.

Plastigage is soluble in oil: therefore, oil on the journal or bearing could result in erroneous readings.

Place a piece of Plastigage along the width of the bearing insert, install the cap, and torque to specifications.

Remove the bearing cap, and determine the bearing clearance by comparing the squished width of Plastigage to the scale on the Plastigage envelope. Journal taper is determined by comparing the width of the Plastigage strip near its ends. Rotate the crankshaft 90° by hand, to determine journal eccentricity.

Do not rotate the crankshaft with the Plastigage installed. If bearing insert and journal appear intact, and are within tolerances, no further main bearing service is required. If bearing or journal appear defective, cause of failure should be determined before replacement.


Place a prybar between a main bearing cap and crankshaft casting taking care not to damage any journals. Pry backward and forward measure the distance between the thrust bearing (center main) and crankshaft with a feeler gauge. Compare reading with specifications. If too great a clearance is determined, a larger thrust bearing or crank machining may be required. Check with an automotive machine shop for their advice.

Connecting rod clearance between the rod and crankthrow casting can be checked with a feeler gauge. Pry the rod carefully to one side as far as possible and measure the distance on the other side of the rod.


If a journal is damaged on the crankshaft, repair is possible by having the crankshaft machined, after removal from engine to a standard undersize. Consult the machine shop for their advice.


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Fig. Fig. 9 Exploded view of the common block assembly

Fill the oil pump with oil, to prevent cavitating (sucking air) on initial engine start up. Install the oil pump and the pickup tube on the engine. Coat the oil pan gasket as necessary, and install the gasket and the oil pan. Mount the flywheel and the crankshaft vibration damper or pulley on the crankshaft.

Always use new bolts when installing the flywheel. Inspect the clutch shaft pilot bushing in the crankshaft. If the bushing is excessively worn, remove it with an expanding puller and a slide hammer, and tap a new bushing into place.

Position the engine, cylinder head side up. Lubricate the lifters, and install them into their bores. Install the cylinder head, and torque it as specified. Insert the pushrods (where applicable), and install the rocker shaft(s) (if so equipped) or position the rocker.

Install the intake and exhaust manifolds, the carburetor(s), the distributor and spark plugs. Mount all accessories and install the engine in the car. Fill the radiator with coolant, and the crankcase with high quality engine oil.


Start the engine, and allow it to run at low speed for a few minutes, while checking for leaks. Stop the engine, check the oil level, and fill as necessary. Restart the engine, and fill the cooling system to capacity. Check and adjust the ignition timing. Run the engine at low to medium speed (800-2,500 rpm) for approximately 1 / 2 hour, and retorque the cylinder head bolts. Road test the car, and check again for leaks.

Some gasket manufacturers recommend not retorquing the cylinder head(s) due to the composition of the head gasket. Follow the directions in the gasket set.