ATK GM 350 390 HP HP89M Stage 2 Mid-Dress Performance

Description

Cam lobe erosion and timing slip sap work truck acceleration under heavy payloads. The ATK GM 350 390 HP HP89M Stage 2 Mid-Dress Performance powerplant solves field fleet downtime through a turnkey industrial engine rebuild. This 5.7L 8-Cylinder build delivers 390HP, though technicians must verify ignition advance curves to avoid detonation on standard pump gasoline.

Using an ASTM A48 Class 30 gray iron block, this ATK engine core incorporates A356-T6 aluminum cylinder heads and an iron crankshaft. Cold electrical starter draw registers 165A on 12V systems. Total dry weight measures 445 lbs inside a 28in length, 26in width, 27in height envelope requiring 5.0 quarts oil.

Key Features of ATK HP89M

Service facilities buy ATK GM 350 390 HP HP89M Stage 2 Mid-Dress Performance engines to bypass the time sink of sourcing intake manifolds and dress accessories separately. The factory-matched aluminum intake manifold optimizes mixture velocity into the combustion chambers for broad street torque.

• Standard 4.000in bore and 3.480in stroke geometry maintains proven small block serviceability.
• Mid-dress packaging includes the performance intake manifold and water pump for expedited bay installs.
• Hydraulic roller valvetrain components eliminate cam break-in failures associated with flat-tappet designs.
• Fast-burn combustion chambers in the aluminum heads promote complete fuel burning efficiency.
• HP89M commercial core machining guarantees deck parallelism across both cylinder banks.
• High-strength rod bolts resist stretch during extended high-rpm passing maneuvers.
• Heavy-gauge stamped steel valve covers prevent nuisance perimeter oil leaks onto exhaust headers.

Test Stand Dynamometer Specifications

Dyno validation confirms raw performance metrics on each HP89M long block engine. Peak output records 390HP at 5300 RPM along with 410 ft-lbs torque at 3900 RPM. Oil gallery pressure maintains 55 PSI hot at 195°F oil temperature. Cylinder compression balances out at 180 PSI across all ports with 3% variance. Crank runout limits at 0.0003in TIR. Exhaust gas temp tops out at 1290°F under maximum dyno torque resistance.

Operational Exclusions Setup Protocols

Accelerator pedal pull resistance requires 5 lbs force. This mid-dress small block is NOT compatible with computer-controlled drive-by-wire pickups, front-wheel-drive configurations, or modern variable valve timing chassis control modules.

• Drain break-in motor oil and renew the oil filter after the first 500 road miles.
• Confirm valvetrain preload at one-half turn down from zero lash during initial checkups.
• Check water pump mounting bolt torque at 30 ft-lbs after the initial engine warm-up run.

Factory Guarantee Crate Inclusions

Assembled to strict ATK assembly standard guidelines, this engine provides a 2-Year 24,000-mile commercial warranty. Each shipping crate contains the mid-dressed engine, intake manifold, water pump, valve covers, oil pan with pickup, and an official signed dyno testing sheet.