Securing Flywheels onto Crankshafts for Engine Integrity

  • Post last modified:October 10, 2025

Mounting a flywheel onto a crankshaft is one of the highest-stress applications in an engine. The joint is subjected to massive and rapidly fluctuating torsional shock (from combustion pulses), high inertia loads (especially during start-up and shifting), and severe heat from the engine block. Flywheels are typically secured with bolts and a precision register fit, but the retaining compound fills any minute clearance, eliminating the possibility of fretting corrosion, shifting, and bolt fatigue. This application demands the absolute highest structural strength to ensure engine reliability and longevity.

INCURE WeldLock™ 365 Retaining Compound

For securing flywheels—where maximum shear strengthhigh-temperature resistance, and torsional stability are paramount—the WeldLock™ 365 is the only choice. Its superior strength converts the registered fit into a permanent,high-integrity bond, resisting the relentless shock and cyclical loads inherent in internal combustion engines.

Feature & BenefitTechnical Insight for Flywheel AssembliesConversion Value
Highest Strength (365)Cures to an extremely high-shear strength, rigid plastic, providing maximum resistance to torsional shock and cyclical fatigue.Zero Fretting: 
Eliminates all micro-movement between the register and the crankshaft, preventing accelerated wear.
High Temperature ResistanceWithstands continuous operational temperatures up to 200∘C (392∘F), essential for components bolted directly to the hot engine block.End the Heat Threat: 
Ensures the bond remains rigid and strong under maximum engine thermal load.
Fills Close Clearance GapsIdeal for the precision register fit (less than 0.05 mmdiametral clearance) of crankshaft components.Maximizes Contact: 
Converts the fit into an integrated component, optimizing balance and load distribution.
Oil & Fuel ImmunityInert to engine oil and combustion byproducts, ensuring the integrity of the joint is protected within the engine environment.Reliability Assured: 
The bond remains permanently intact throughout the engine’s lifespan.

Application Steps: Locking Flywheels for Maximum Engine Reliability

Preparation (Critical): Thoroughly clean both the flywheel register bore and the crankshaft mating surface. Remove all oil, grease, paint, and residue. Use a degreasing solvent (like acetone or brake cleaner) and wipe until both metal surfaces are perfectly dry.

Application: Apply a continuous, liberal bead of WeldLock™ 365 evenly around the crankshaft register or the inside circumference of the flywheel bore. Ensure the compound completely covers the mating area.

Assembly: Mount the flywheel onto the crankshaft. Install the flywheel bolts and torque them to the manufacturer’s specified pattern and value immediately.

Curing Time (Mandatory): Allow a full 24 hours for the compound to reach full cure strength before starting the engine or subjecting the assembly to load.

Stop risking crank and flywheel damage, and ensure your engine’s power transmission is absolutely permanent.