ATK High Performance GM 383 TBI Stroker 320 HP Stage 1 Long Block – HP05
The ATK High Performance GM 383 TBI Stroker 320 HP Stage 1 Long Block is engineered for enthusiasts seeking more torque, horsepower, and throttle response from their factory TBI-equipped small block Chevy. Designed as a direct bolt-in upgrade for 1987–1995 GM trucks, SUVs, and cars with throttle body injection, this crate engine delivers the perfect blend of streetable performance and reliability.
Key Features
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Horsepower: 320 HP @ 4,500 RPM
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Torque: 410 lb-ft @ 3,500 RPM
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Displacement: 383 cu. in. (6.3L) Stroker
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Compression Ratio: 9.3:1 (optimized for pump gas)
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Block Material: Seasoned OE cast iron
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Cylinder Heads: Reconditioned iron heads, 1.94” intake / 1.50” exhaust valves
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Camshaft: Hydraulic flat tappet cam for improved low-end torque and midrange pull
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Induction: Works with factory GM TBI system (requires ECM recalibration for optimal performance)
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Balanced Assembly: Internal balance for smooth operation
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Oil Pan: Standard 5-quart
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Fuel Compatibility: Unleaded pump gas
Included Components
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Complete assembled long block
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OE reconditioned connecting rods
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Hypereutectic pistons
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Performance camshaft & lifters
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Timing set
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Cylinder heads installed and torqued
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Oil pump & pick-up tube
Recommended Upgrades
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Performance TBI unit or modified injectors
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Headers & free-flowing exhaust
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ECM tuning for maximum gains
Applications
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1987–1995 GM trucks & SUVs with 5.7L TBI
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Classic Chevy street trucks
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Budget-friendly stroker swaps
Why Choose ATK?
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Built with high-quality components
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Dyno-tested for proven performance
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Backed by ATK’s industry-leading warranty
⚡ Turn your TBI small block into a torque monster with the ATK GM 383 TBI Stroker HP05 – the perfect balance of OEM fitment and big-displacement grunt.
Comparison Chart: ATK HP05 vs. ATK HP74 vs. BluePrint BP383
| Feature / Spec | ATK HP05 GM 383 TBI Stroker | ATK HP74 GM 350 Vortec | BluePrint BP383 GM 383 Stroker |
|---|---|---|---|
| Displacement | 383 cu. in. (6.3L) | 350 cu. in. (5.7L) | 383 cu. in. (6.3L) |
| Horsepower | 320 HP @ 4,500 RPM | 315 HP @ 5,000 RPM | 430 HP @ 5,500 RPM |
| Torque | 410 lb-ft @ 3,500 RPM | 385 lb-ft @ 3,800 RPM | 450 lb-ft @ 4,500 RPM |
| Compression Ratio | 9.3:1 | 9.1:1 | 10.0:1 |
| Cylinder Heads | Reconditioned iron heads, 1.94” / 1.50” valves | Vortec iron heads, 1.94” / 1.50” valves | Aluminum heads, 2.02” / 1.60” valves |
| Camshaft | Hydraulic flat tappet | Hydraulic flat tappet | Hydraulic roller |
| Fuel System Compatibility | GM TBI (ECM tune recommended) | Carbureted or Vortec EFI | Carbureted (can be adapted to EFI) |
| Intended Use | 1987–1995 GM trucks/SUVs, direct TBI replacement with more power | Street trucks, muscle cars, hot rods | High-performance street/strip |
| Warranty | 3 years | 3 years | 30 months |
| Fitment Notes | Direct fit for OEM TBI vehicles | May require intake manifold match | Requires performance intake & fuel system |
Frequently Asked Questions – ATK HP05 GM 383 TBI Stroker
1. Will the ATK HP05 work with my stock GM TBI system?
Yes, it’s designed to bolt in and work with the factory GM TBI setup from 1987–1995. For optimal performance, we recommend an ECM recalibration and upgraded injectors.
2. Do I need a different torque converter or transmission upgrade?
In most cases, the stock transmission will work fine, but if you have high mileage or plan to tow/haul, consider a fresh rebuild or a shift kit.
3. What is the break-in procedure for this engine?
Use conventional 10W-30 break-in oil for the first 500 miles, avoid sustained high RPMs, and change the oil & filter at 500 miles. Follow ATK’s official break-in guide.
4. What fuel octane is recommended?
The HP05 runs on 87 octane pump gas, but using 89 or 91 octane may provide slightly better performance under heavy load.
5. Can I run headers with this engine?
Yes, headers will improve performance and efficiency. Pair them with a free-flowing exhaust for maximum gains.
6. How much horsepower can I expect after ECM tuning and bolt-on upgrades?
With a performance TBI unit, headers, and a custom tune, it’s possible to see 340–350 HP while maintaining reliability.
7. Is this engine emissions-legal?
Yes, when installed in its intended model years (1987–1995) with factory TBI equipment and emissions controls intact.
8. What warranty coverage does ATK provide?
ATK offers a 3-year warranty against defects in materials and workmanship. Performance modifications may void coverage—check terms before upgrading.
