Product Description
The ATK HP31 Chevrolet 350ci TBI High-Performance Crate Engine is a professionally assembled small-block V8 designed for compatible 1987–1995 Chevrolet and GMC trucks originally equipped with a 350 cubic-inch throttle-body-injected engine.
Delivering an advertised 290 horsepower and 373 lb-ft of torque, this performance engine provides an upgraded power configuration while retaining compatibility with many original GM truck components.
The HP31 is built around a seasoned 1987–1995 Chevrolet OE engine block featuring four-bolt main construction and a one-piece rear main seal. Its traditional 350 cubic-inch displacement combines proven Chevrolet small-block architecture with carefully selected performance components.
The engine uses an OE reground crankshaft, 5.7-inch powder-metal connecting rods, hypereutectic pistons, moly piston rings, and a 9.1:1 compression ratio. These components provide the internal foundation for the HP31’s performance configuration.
One of the key performance upgrades is its hydraulic roller camshaft, featuring 198° intake and 210° exhaust duration at .050-inch lift. This camshaft works with the OE TBI cast-iron cylinder heads to support the engine’s advertised horsepower and torque.
The cylinder heads feature 67cc combustion chambers, 1.94-inch intake valves, and 1.50-inch exhaust valves. Combined with stamped-steel rocker arms, the valvetrain preserves much of the traditional GM small-block construction.
The ATK HP31 is designed to work with many original vehicle components, making it attractive for classic Chevrolet and GMC truck owners who want improved engine performance without completely changing the vehicle’s original TBI architecture.
However, the vehicle’s engine control module requires appropriate calibration for proper operation. ATK also recommends compatible intake and exhaust upgrades when aiming to achieve the advertised performance figures.
As a base engine, the HP31 includes the main engine assembly and internal components but does not include every external accessory. Its configuration allows customers and professional installers to select compatible intake, ignition, cooling, and fuel-system components based on their vehicle requirements.
For Chevrolet and GMC truck restoration projects, the ATK HP31 350ci TBI Performance Engine offers a useful combination of traditional GM compatibility, improved engine output, and professionally assembled internal components.
Key Features
290 Horsepower Performance
Produces an advertised 290HP for compatible Chevrolet small-block TBI applications.
373 lb-ft Torque
Delivers 373 lb-ft of advertised torque, supporting strong performance in appropriately configured GM trucks.
Chevrolet 350ci Small Block V8
Features the traditional 5.7L Chevrolet small-block architecture used in numerous GM truck applications.
Designed for 1987–1995 TBI Trucks
Intended primarily for compatible Chevrolet and GMC trucks originally equipped with 350ci throttle body injection.
Four-Bolt Main Engine Block
Built around a seasoned OE four-bolt-main block with a one-piece rear main seal.
Hydraulic Roller Camshaft
Features a performance hydraulic roller camshaft designed for the engine’s power characteristics.
OE TBI Cast-Iron Cylinder Heads
Uses GM-compatible TBI cylinder heads with 67cc combustion chambers.
9.1:1 Compression Ratio
Equipped with hypereutectic pistons and a 9.1:1 compression configuration.
Double-Roller Timing Chain
Features a double-roller timing set as part of the performance engine assembly.
Original Component Compatibility
Designed to retain compatibility with many stock engine components, subject to proper calibration and application fitment.
Performance Base Engine Configuration
Provides the assembled engine foundation for customers using suitable existing or replacement external components.
Technical Specifications
| Specification | Details |
|---|---|
| Manufacturer | ATK High Performance |
| Model | HP31 |
| Engine Category | Performance Base Engine / Long Block |
| Engine Family | Chevrolet Small Block V8 |
| SKU | ATK-HP31-350TBI-1897 |
| Displacement | 350ci / 5.7L |
| Cylinder Configuration | V8 |
| Advertised Horsepower | 290 HP |
| Advertised Torque | 373 lb-ft |
| Engine Block | 1987–1995 OE Block |
| Main Bearing Configuration | 4-Bolt Main |
| Rear Main Seal | One-Piece |
| Bore | 4.040 Inches |
| Stroke | 3.480 Inches |
| Compression Ratio | 9.1:1 |
| Crankshaft | OE Reground |
| Crankshaft Balance | Internal Front / External Rear |
| Connecting Rods | OE Powder Metal, 5.7 Inches |
| Pistons | Hypereutectic |
| Piston Rings | Moly |
| Camshaft Type | Hydraulic Roller |
| Intake Cam Duration @ .050 | 198° |
| Exhaust Cam Duration @ .050 | 210° |
| Intake Valve Lift | .435 Inches |
| Exhaust Valve Lift | .462 Inches |
| Lobe Separation Angle | 116° |
| Timing Chain | Double Roller |
| Cylinder Head Material | Cast Iron |
| Cylinder Head Type | OE TBI |
| Combustion Chamber | 67cc |
| Intake Valve Size | 1.94 Inches |
| Exhaust Valve Size | 1.50 Inches |
| Rocker Arms | Stamped Steel |
| Rocker Ratio | 1.5:1 |
| Oil Pan | Rear Sump |
| Oil Pan Capacity | 5 Quarts |
| Oil Pump | Melling Standard Volume |
| Fuel System Compatibility | GM TBI |
| Recommended Fuel | 91+ Octane |
| Engine Control Module | Calibration Required |
| Condition | Professionally Remanufactured |
Engine Block / Internal Configuration
| Component | Details |
|---|---|
| Engine Block | Chevrolet OE Cast-Iron Block |
| Block Years | 1987–1995 |
| Engine Displacement | 350 Cubic Inches |
| Bore × Stroke | 4.040″ × 3.480″ |
| Main Bearings | 4-Bolt Main |
| Rear Main Seal | One-Piece |
| Crankshaft | OE Reground |
| Connecting Rods | OE Powder Metal, 5.7″ |
| Pistons | Hypereutectic |
| Compression Ratio | 9.1:1 |
| Piston Rings | Moly |
| Timing Chain | Double Roller |
The HP31’s small-block construction allows it to work with many factory-based Chevrolet 350 TBI vehicle configurations when professionally installed and correctly calibrated.
Cylinder Head / Valvetrain Configuration
| Component | Details |
|---|---|
| Cylinder Heads | OE TBI Cast Iron |
| Combustion Chamber | 67cc |
| Intake Valve Diameter | 1.94 Inches |
| Exhaust Valve Diameter | 1.50 Inches |
| Camshaft | Hydraulic Roller |
| Intake Duration @ .050 | 198° |
| Exhaust Duration @ .050 | 210° |
| Intake Cam Lift | .435 Inches |
| Exhaust Cam Lift | .462 Inches |
| Lobe Separation | 116° |
| Rocker Arms | Stamped Steel |
| Rocker Ratio | 1.5:1 |
Fuel / Intake Configuration
| Component | Details |
|---|---|
| Fuel System Compatibility | Throttle Body Injection |
| Original Application | 1987–1995 GM 350 TBI |
| Intake Manifold | Not Included |
| Compatible Intake | Original GM or Appropriate Aftermarket TBI |
| Recommended Aftermarket Intake | Edelbrock 3704 |
| Fuel Injection Assembly | Not Included |
| ECM Calibration | Required |
| Recommended Fuel | 91+ Octane |
The HP31 is designed for customers retaining a compatible GM throttle-body-injection system. Proper engine control calibration is required for the upgraded engine configuration.
Ignition / Electrical Configuration
| Component | Details |
|---|---|
| Ignition System | GM TBI-Compatible |
| Distributor | Application-Specific |
| Recommended Spark Plugs | Autolite 605 |
| Spark Plug Wires | Factory-Compatible Replacements |
| Spark Plug Gap | .035 Inches |
| Engine Computer | Not Included |
| ECM Calibration | Required |
| Ignition Timing | Set According to Applicable Engine Calibration |
Cooling / Lubrication Configuration
| Component | Details |
|---|---|
| Oil Pump | Melling Standard Volume |
| Oil Pan | Rear Sump |
| Oil Capacity | 5 Quarts |
| Recommended Oil | Conventional 10W-30 |
| Oil Filter | Compatible Wix or K&N |
| Water Pump | Not Included |
| Cooling Equipment | Application-Specific |
| Maintenance | Follow ATK Engine Documentation |
Engine Balance / Drivetrain Configuration
| Component | Details |
|---|---|
| Front Crankshaft Balance | Internal |
| Rear Crankshaft Balance | External |
| Recommended Harmonic Balancer | PowerBond PB1046-N |
| Recommended Flexplate | Pioneer FRA-159 |
| Rear Main Seal | One-Piece |
| Torque Converter | Stock-Compatible Configuration |
| Transmission Compatibility | Application-Specific |
What’s Included
| Included Component | Details |
|---|---|
| ATK HP31 Chevrolet 350ci Engine | 1 Unit |
| OE Four-Bolt-Main Engine Block | Included |
| OE Reground Crankshaft | Installed |
| Powder-Metal Connecting Rods | Installed |
| Hypereutectic Pistons | Installed |
| Moly Piston Rings | Installed |
| Hydraulic Roller Camshaft | Installed |
| Double-Roller Timing Chain | Installed |
| OE TBI Cast-Iron Cylinder Heads | Installed |
| Stamped-Steel Rocker Arms | Installed |
| Oil Pan | Included |
| Oil Pump | Included |
| Valve Covers | Included |
| Timing Cover | Included as part of engine assembly |
| Intake Manifold | Not Included |
| TBI Injection Unit | Not Included |
| Carburetor | Not Included |
| Harmonic Balancer | Not Included |
| Flexplate / Flywheel | Not Included |
| Water Pump | Not Included |
| Distributor | Not Included |
| Additional External Accessories | Not Included Unless Specified |
Vehicle / Installation Compatibility
The ATK HP31 is designed primarily for 1987–1995 Chevrolet and GMC trucks equipped with a 350ci TBI engine.
| Vehicle Application | Compatibility Considerations |
|---|---|
| Chevrolet C/K Trucks | 350 TBI Engine Configuration |
| GMC C/K Trucks | Engine Mounting and ECM Calibration |
| Chevrolet Suburban | Application-Specific Fitment |
| GMC Suburban | Application-Specific Fitment |
| Chevrolet Blazer | Compatible 350 TBI Applications |
| GMC Full-Size Utility Vehicles | Engine and Drivetrain Verification |
| Custom Truck Projects | Suitable Chevrolet Small-Block Configuration |
Vehicle year and engine displacement alone do not guarantee fitment. Original engine configuration, transmission, electrical system, oil pan clearance, and emissions requirements must be checked.
Ideal Applications
Classic GM Truck Restoration: Suitable for restoring compatible Chevrolet and GMC trucks with 350 TBI engine systems.
Performance Engine Replacement: Provides a performance-oriented replacement option for applicable 1987–1995 GM truck configurations.
Truck Rebuilding Projects: Useful for professionally planned engine restoration and rebuilding projects.
Automotive Workshops: Suitable for professional engine replacement services requiring a compatible Chevrolet 350 TBI long block.
GM Small-Block Projects: Provides a familiar engine foundation for suitable Chevrolet small-block applications.
Product Advantages
The ATK HP31 combines a proven GM 350 small-block platform with a performance hydraulic roller camshaft, upgraded internal components, and OE-compatible TBI cylinder heads.
Its 290HP and 373 lb-ft torque rating makes it an attractive performance replacement for compatible GM truck owners seeking additional power while preserving much of their vehicle’s original engine configuration.
The base-engine package also allows professional installers to select and reuse appropriate external components.
Safety & Installation Notice
Professional automotive installation is recommended.
Confirm engine fitment, ECM calibration requirements, fuel delivery, intake compatibility, ignition equipment, drivetrain components, cooling equipment, and applicable emissions regulations.
This engine should not be assumed legal for pollution-controlled vehicles without verifying the specific installation’s compliance.
Warranty Information
2-Year Limited Warranty
Reviews
There are no reviews yet.