How much horsepower can a TBI 350 make?
In brief, a Chevrolet 5.7-liter V8 with throttle-body injection (TBI) typically produces roughly 190–230 horsepower from the factory, with some late‑1980s to early‑1990s variants nudging toward the low 240s. With common bolt‑on upgrades and a tuning job, enthusiasts often reach about 260–320 horsepower, and with forced induction the figure can exceed 400 horsepower given the right supporting equipment.
To understand why those numbers vary and what it takes to push a TBI 350 toward higher power, this article explains the baseline, the limiting factors, and practical upgrade paths for streetable builds on this era engine.
Stock horsepower baseline
These figures reflect typical factory ratings for the 5.7L V8 used with throttle-body injection in GM trucks, vans, and some full-size cars during the late 1980s and early 1990s. Actual numbers can differ by vehicle, emissions package, and whether the rating is SAE net or older gross measurements.
- 1987–1990 GM trucks and vans with a 5.7L TBI: approximately 190–210 horsepower, with torque commonly in the 300–320 lb-ft range.
- 1991–1993 models: roughly 210–230 horsepower, with torque typically around 320–350 lb-ft.
- Mid‑ to late‑1990s applications with continued EFI evolution: commonly about 230–240 horsepower, with torque near 320–350 lb-ft.
In practice, these numbers vary by exact model, market, and calibrations used by the manufacturer for emissions and drivability. For precise figures, check the vehicle’s original window sticker or GM documentation for the specific VIN engine code.
Why those numbers vary
The horsepower you see on a TBI 350 is influenced by emissions equipment, intake/exhaust configuration, and the specific calibration used in a given model year. Changes in fuel delivery, ignition timing, and even seasonal recalibrations can shift the published figure by a few horsepower, so the headline number isn’t always the full story of how the engine will behave in real-world driving.
Paths to higher power on a TBI 350
Below are common upgrade categories and the typical horsepower impact they can offer on a TBI 350. The ranges assume you’re installing compatible parts and running a proper tune, with attention to fuel delivery and cooling needs.
- Bolt‑on exhaust, intake, and throttle body upgrades: typically 15–40 hp gains.
- Camshaft swap combined with optimized ignition and fueling: about 20–80 hp gains, depending on the cam profile and compression setup.
- Cylinder head work or aftermarket heads with improved flow: roughly 20–70 hp additional after other supporting modifications.
- Ignition system improvements and ECU tuning: about 10–30 hp gains
- Forced induction (turbo or supercharger) with appropriate fuel system and intercooling: typically 150–300+ hp gains, highly dependent on boost level and supporting hardware.
Note that increasing power reliably often requires addressing fuel delivery, cooling, and engine internals. A well-planned build with proper fuel, ignition, and cooling upgrades is essential to maintain drivability and longevity.
Important constraints to keep in mind
While the potential for horsepower is real, the TBI era 5.7L block isn’t built for extreme performance without upgrades. Pistons, rods, and bearings may become stressed with high compression or boost; the fuel system and ignition components must keep pace; and cooling must be adequate for higher loads. Budget, reliability, and daily drivability should guide how aggressively you push the power target.
Real-world takeaway and expectations
For most enthusiasts aiming for a balanced streetable setup, a TBI 350 with a sensible mix of bolt‑ons and a tune can reach the mid‑200s to low‑300s horsepower. More aggressive cam and head work can push this higher, while forced induction dramatically increases power but adds complexity and maintenance. Always plan around octane requirements, fuel delivery capacity, and cooling performance to avoid drivability issues.
Summary
The TBI 350 typically makes about 190–230 horsepower in stock form, with some variants at the higher end of that range. Upgrades such as exhaust, intake, and tuning can push power into the 260–320 hp range for naturally aspirated builds, while forced induction can surpass 400 hp with comprehensive supporting upgrades. Real-world results depend on year, emissions equipment, and the quality of the build, so a careful plan is essential for reliable, higher-powered performance.
