ATK GM 365 LQ4 550 HP LQ4-LB-1 Stage 1 Long Block

Description

Pushrod deflection and lifter bore scoring sap top-end acceleration on commercial utility haulers under continuous highway transit. The ATK GM 365 LQ4 550 HP LQ4-LB-1 Stage 1 Long Block remedies valvetrain instability through an industrial engine rebuild. This 6.0L 8-Cylinder build develops 550HP, requiring mechanics to verify cam thrust plate O-ring seal seating to stop internal oil leaks.

Cast from ASTM A48 Class 35 cast iron, this ATK engine core incorporates free-breathing A356-T6 aluminum heads and a 4140 forged steel crankshaft. Starter draw demands 170A on 12V systems. Bare engine weight reaches 465 lbs inside 28in length, 26in width, 27in height dimensions with 6.0 quarts oil capacity.

Key Features of ATK LQ4-LB-1

Transport shops buy ATK GM 365 LQ4 550 HP LQ4-LB-1 Stage 1 Long Block assemblies to deploy serious naturally aspirated iron-block power into commercial truck engine compartments. Deep-skirt iron block construction braces the rotating assembly against catastrophic case warping during protracted uphill trailer towing.

• Standard 4.000in bore and 3.622in stroke geometry preserves proven iron-block LS reliability.
• High-velocity aluminum cylinder heads optimize fuel atomization for crisp throttle transitions.
• Hydraulic roller valvetrain components eliminate cam break-in failures associated with flat-tappet designs.
• Scat forged steel I-beam rods resist bending forces during hard trailer engine braking.
• LQ4-LB-1 commercial core line-hone tolerances guarantee optimal hydrodynamic oil clearance.
• Deep-skirt iron block casting provides exceptional structural stiffness under high cylinder pressure.
• Heavy-duty double roller timing set maintains exact valve timing across severe duty cycles.

Test Bench Dyno Limits

Dyno validation confirms raw performance metrics on each LQ4-LB-1 long block engine. Peak output records 550HP at 6200 RPM along with 490 ft-lbs torque at 4600 RPM. Oil gallery pressure maintains 58 PSI hot at 195°F oil temperature. Cylinder compression balances out at 190 PSI across all ports with 3% variance. Crank runout limits to 0.0003in TIR. Exhaust gas temp tops out at 1320°F under maximum dyno torque resistance.

Bay Constraints Maintenance Schedule

Throttle return linkage pull measures 5 lbs force. This high-performance iron LS engine is NOT suited for original low-pressure fuel delivery systems, factory stock 87-octane fuel, or transverse front-wheel-drive chassis.

• Flush break-in engine oil and replace the filter element after 500 highway transit miles.
• Set hydraulic roller lifters to factory preload specs when performing cold adjustments.
• Retorque valve cover perimeter bolts to 106 in-lbs following initial temperature cycles.

Factory Guarantee Crate Inclusions

Adhering to the verified ATK assembly standard, this heavy-duty unit carries a 2-Year 24,000-mile commercial warranty. Each shipping crate contains the assembled long block engine, oil pan, valve covers, front timing cover, oil pump with screen, and an official signed dyno verification sheet.