General Motors engineers redesigned and reproduced the crankshafts for small-block V8 and V6/90-degree engines in 1986. The new model used a leak-resistant one-piece rear seal, which required a change in the bolt pattern on the crankshaft flywheel flange. The manual transmission flywheels and automatic transmission flex plates are used with Chevrolet small-block V8 and 90-degree V6 engines. Operators should match the outside diameter of the flywheel flange bolt pattern when selecting a flywheel or flexplate. GM offers lightweight iron flywheels and flexplates suitable for pre-1985 and 1986 onward engines. These flywheels (flexplates) reduce an engine's inertia and improves the throttle response.
Things You'll Need
- Torque wrench
- Alignment pin
- Flexplate component
- Thread sealant
Torque all crankshaft bolts to the appropriate sequence of 58 feet per pound. Insert the alignment pin between the new flexplate component and the crankshaft hub for guaranteed alignment. Torque all crankshaft locking bolts to sequence of 60 degrees.
Torque all crankshaft bolts another 60 degrees in sequence. Do not over-torque the crankshaft bolts by combining steps 1 and 2 and torquing the bolts 120 degrees at one time. Confirm that the torque value reads at least 266 feet per pound with a torque wrench.
Turn on the ignition and start the vehicle. Allow the vehicle to run in idle until it reaches the normal temperature. Sit in the cab and listen for unusual vibrations or sounds at various rotations per minute, or RMP. An abnormal vibration indicates improper installation of the alignment pin, which caused the flexplate to index incorrectly. The flexplate must be removed and reinstalled if the alignment pin was inappropriately installed the first time. Shut off the engine once reaching the normal operating temperature.
Rotate the crankshaft until the flexplate oval hole becomes visible through the starter access cavity. Apply a small bead of thread sealant to all of the torque converter bolts. Thread and hand-tighten each torque converter bolt.
Torque each bolt within a sequence of 44 feet per pound. Confirm the final torque by tightening each bolt an additional 44 feet per bound while using the same sequence. Do not combine each torque because it will cause damage to your vehicle.
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