This page highlights second gen 12-valve upgrades and fit notes. For first gen or later engines, use the links at the bottom. Detailed specs, year breaks, and exact kit contents are listed on each product page.
Why upgrade your 1994–1998 12V Cummins
- Stronger towing and midrange: Flow-optimized manifolds and right-sized turbos help the engine hold speed on grades with lower EGT.
- Quicker spool and response: Efficient collectors and clean hot-side routing improve low rpm boost for street and tow manners.
- Durability: Thick-wall castings with flat-machined flanges resist warping and leaks through repeated heat cycles.
- Clean fitment: Parts modeled around second gen bay clearances for service access and repeatable installs.
Is the 12V Cummins good for towing
Yes. The 5.9 12-valve is known for low-rpm torque and mechanical simplicity, which make it a strong towing platform. Upgrading the manifold and turbo improves airflow and reduces drive pressure so the truck pulls steadier with cooler temps.
How can I improve performance on my 1994–1998 12V
Start with a high-flow manifold and a turbo sized to your load and elevation. Add monitoring for EGT and boost. If fueling is increased, match turbine housing area to maintain response. The right combination delivers stronger acceleration and better grade control without sacrificing drivability.
How to choose parts for a second gen 12V
- Towing and daily use: Stock-replacement or T3 manifold with a quick-spooling turbo. Monitor EGT on first towing runs.
- Street performance: Mid-size compressor with the correct turbine A/R to hold speed on grades without excessive lag.
- Higher fuel builds: Larger airflow with freer housings and adequate intercooling. Plan converter, gearing, and brakes for the target power.
Fitment checklist for 1994–1998
- Confirm T3 vs T4 manifold flange for your turbo choice.
- Verify downpipe route, intercooler path, and clearance at steering shaft and A/C lines.
- Plan new gaskets, quality hardware, heat shielding, and ports if logging EGT or drive pressure.
Install and first drive notes
- Use new gaskets and quality hardware. Torque in sequence on a cold engine.
- Pressure test the charge-air system before first start. Check for any pre-turbine leaks.
- Monitor boost and EGT on shakedown. Re-check fasteners after heat cycles if specified.
Shopping related categories? 5.9 Cummins Manifolds (12V, 24V, common-rail) | S300 Single Turbos | S400 Single Turbos | Add-A-Turbo Kits. For earlier trucks see First Gen 12V (1989–1993).
Frequently asked questions
Do I need tuning after a manifold swap on a 12V
A manifold alone does not require tuning. If turbo size or fueling changes, adjust fuel delivery and monitor EGT for safe operation.
Will a performance manifold lower tow temps
Yes. Lower drive pressure and smoother flow typically reduce EGT on long pulls and help the turbo stay in an efficient range.
T3 or T4 on a second gen 12V
Choose T3 for most stock-frame or quick-spool goals. Move to T4 when stepping up airflow with future power headroom.
What should I inspect during install
Manifold and turbo sealing faces, downpipe alignment, intercooler boots, and any soot traces that indicate a pre-turbine leak.
