Engine Connecting Rod 8-94391791-0 8-98018425-2 For ISUZU 6HK1 4HK1 6HK1T NPR NQR NRR FSR FVR Hitachi ZX Excavator — OEM Verified Forged Steel, Full-Floating Pin Bushing, Lock-to-Lock

The Engine Connecting Rod with OEM references 8-94391791-0 and 8-98018425-2 is a verified direct-fit replacement for ISUZU 6HK1 (7.8L) and 4HK1 (5.2L) diesel engines. This connecting rod is the critical link between the piston and the crankshaft, transmitting combustion force from the piston pin to the crankshaft journal and converting linear piston motion into rotational power. The 6HK1 is a 7,790 cc inline-6 OHC diesel used in ISUZU FSR, FVR, and FVZ trucks as well as Hitachi ZX-series excavators, while the 4HK1 is a 5,193 cc inline-4 used in NPR, NQR, and NRR commercial trucks.

This connecting rod features a full-floating piston pin design with a serviceable small-end bushing, a forged steel construction (40Cr or 42CrMo4, normalized and induction-hardened), and a lock-to-lock bearing retention design that secures the bearing shells precisely in the rod and cap. The rod is available in 4HK1-length (205 mm center-to-center) and 6HK1-length (210 mm center-to-center) configurations. The 8-98018425-2 reference is the more current and widely stocked number, while 8-94391791-0 is the earlier/legacy reference associated with the 6HK1 platform.

• Material Verified: 40Cr forged (multiple supplier listings) or 42CrMo4 normalized and induction-hardened; one supplier specifies forged 4340 steel.
• Dimensional Data Verified: Center-to-center length 205 mm (4HK1) / 210 mm (6HK1); large-end bore 61 mm; small-end bore 38 mm. Another source lists 78 mm large-end / 40 mm small-end / 33 mm thickness / 188 mm center-to-center for a specific 6HK1 variant — confirm the exact variant.
• Weight Verified: 1.85 kg (rod assembly, without bearings) per Russian technical listing; 2 kg per another supplier.
• Design Feature Verified: Full-floating piston pin design with a serviceable small-end bushing; ISUZU replacement bushings require material removal to achieve proper pin fit.
• Equipment Coverage Verified: Compatible with Hitachi ZX200-3, ZX225, ZX240-3, ZX270, ZX330; JCB; Case CX series; and ISUZU NPR / NQR / NRR / FSR / FVR / FVZ trucks.

• Deep metallic knocking from the engine block (rod knock): The most recognizable symptom. A worn large-end bearing or stretched rod produces a heavy, rhythmic knock that intensifies under load and may diminish when the cylinder is disabled during diagnostics.
• Low oil pressure and metal debris in oil: Bearing material suspended in the oil, often with a glittering appearance, indicates rod bearing degradation.
• Excessive piston pin noise (double knock): A worn small-end bushing produces a sharp double-knock at idle and low speed, especially noticeable on cold start.
• Bent or stretched rod after overheating or hydrolock: A connecting rod subjected to thermal distortion or liquid ingress may be bent beyond specification even without visible cracking. Rods should be measured for bend and twist during any major overhaul.
• Visible cracking at the rod cap or beam: Cracks in the forged beam or at the cap mating surface require immediate replacement — a fractured rod can exit the block and destroy the engine.
• Uneven bearing wear pattern: A rod that is bent or twisted will produce an asymmetric bearing contact pattern, indicating the rod itself must be replaced, not just the bearings.

Compatible with Hitachi ZX200-3, ZX225, ZX240-3, ZX270, ZX330 excavators, as well as JCB and Case CX series equipment.

1. Confirm the original rod dimensions: Measure the removed rod’s center-to-center length (205 mm vs. 210 mm), large-end bore, small-end bore, and lock orientation (same-side vs. opposite-side). Match the new rod to these dimensions exactly.
2. Check rod bend and twist: Even a new rod should be verified for bend and twist on a rod alignment fixture before installation. A bent rod will destroy the bearing and may damage the crankshaft.
3. Fit the small-end bushing: If the bushing is not pre-fitted, press in the new bushing and ream/hone to achieve the specified piston pin clearance. ISUZU replacement bushings reportedly require material removal — do not assume a drop-in fit.
4. Install bearings and lubricate: Seat the bearing shells in the rod and cap, ensuring the lock tangs engage the lock slots correctly. Lubricate the bearing surfaces and crank journal with assembly lubricant.
5. Protect the crank journal: Use rod bolt guides or tape over the rod bolts during installation to prevent scratching the crankshaft journal.
6. Torque rod bolts correctly: Use new rod bolts where specified. Torque in stages to the workshop manual specification, and measure rod bolt stretch if required by the manual. Do not substitute torque for stretch on TTY bolts.
7. Check side clearance and oil clearance: Verify connecting rod side clearance on the crank journal and bearing oil clearance with plastigauge or micrometer measurement. Both must be within specification.
8. Verify piston pin fit: The piston pin should slide through the small-end bushing with the specified interference/clearance. A pin that is too tight will seize; one that is too loose will knock.
9. Rotate the assembly and re-check: After torquing all rods, rotate the crankshaft through two full turns and confirm smooth rotation with no binding or interference.

• Oil changes: Use the correct diesel engine oil and adhere to ISUZU recommended intervals (typically 10,000–15,000 km for commercial truck applications). Degraded oil accelerates rod bearing wear.
• Oil pressure monitoring: A drop in oil pressure or the appearance of a knock warrants immediate investigation — do not continue operating with suspected rod bearing degradation.
• Overhaul inspection: At any major engine overhaul, measure rod bend/twist and inspect the small-end bushing and large-end bearing surfaces. Replace rods that are bent, cracked, or show heat discoloration.
• Matched sets: When replacing rods, use a matched weight set and the same lock orientation across all cylinders to maintain engine balance and bearing retention integrity.

• Standard packing: Neutral carton with protective wrapping; wooden pallet available for bulk export orders.
• Package contents: 1 × Connecting Rod (bearings, bushing, and rod bolts not included unless explicitly stated — confirm at inquiry).
• Set options: Single rod / matched set for one engine (4 pcs for 4HK1 / 6 pcs for 6HK1) — specify at inquiry.
• Suitable for: ISUZU engine rebuilders, Hitachi / JCB / Case equipment repair shops, commercial truck fleet maintenance departments, spare parts distributors, and export wholesalers.
• Related parts available: Rod bearings, small-end bushings, piston pins, rod bolts, and complete 4HK1 / 6HK1 overhaul kits.