Dorman 674-870 Exhaust Manifold Kit Review: Complete Repair Solution That Actually Delivers

When your check engine light illuminates and diagnostic codes point to exhaust manifold failure, you’re faced with a choice: shell out thousands at the dealership or tackle the repair yourself with quality aftermarket parts. After extensively testing the Dorman 674-870 Exhaust Manifold Kit on multiple vehicles, we can confidently say this complete kit bridges the gap between professional-grade quality and DIY affordability.

What immediately impressed us about this exhaust manifold kit wasn’t just the manifold itself—it was Dorman’s thoughtful inclusion of every gasket, bolt, and piece of hardware needed for a successful installation. There’s nothing worse than being elbow-deep in a repair only to discover you’re missing a critical component. Dorman eliminates that frustration entirely.

Why the Dorman 674-870 Stands Out in the Aftermarket Parts Market

Having worked with countless exhaust manifold replacements over the years, we’ve learned that not all aftermarket parts are created equal. The Dorman 674-870 distinguishes itself through engineering improvements that address the very reasons your original manifold likely failed in the first place.

During our hands-on evaluation, we discovered that Dorman didn’t simply copy the OEM design—they enhanced it. The casting quality feels substantial in your hands, with smooth interior passages that promote proper exhaust flow. The heat-resistant coating applied to the manifold surface provides additional protection against the thermal cycling that destroys lesser manifolds over time.

Everything You Need in One Box: The Complete Kit Advantage

Opening the Dorman 674-870 package for the first time, we were genuinely impressed by the completeness of the kit. Here’s exactly what you’ll find inside:

• Precision-cast exhaust manifold built to exact specifications
• High-temperature exhaust manifold gasket designed to withstand extreme heat cycles
• Premium-grade mounting hardware including bolts and studs
• All necessary installation components for a proper seal

This comprehensive approach saved us an estimated 2-3 hours that would have been spent sourcing individual components from multiple suppliers. For DIY mechanics and professional technicians alike, time is money—and this kit respects both.

Our Real-World Installation Experience

We installed the Dorman 674-870 on a compatible vehicle to evaluate fitment, installation ease, and immediate performance. The manifold slid into position with satisfying precision—no wrestling, no forcing, no filing down mounting points. The bolt holes aligned perfectly with the cylinder head, which isn’t always a given with aftermarket parts.

The included gaskets deserve special mention. They’re constructed from multi-layer steel with graphite facing, providing the heat resistance and compression characteristics needed for a lasting seal. During our torque sequence, the gasket compressed evenly without any concerning creaking or cracking sounds that sometimes accompany inferior gaskets.

Installation time clocked in at approximately 3-4 hours for a moderately experienced DIYer with basic hand tools. Professional mechanics will likely complete the job in 2-3 hours. The time investment is absolutely worthwhile when compared to dealership labor rates that can exceed $1,000 for this repair.

Performance Testing: Does It Actually Fix the Problem?

After installation, we conducted comprehensive testing to evaluate real-world performance. The check engine light—previously illuminated due to exhaust manifold cracks—remained off through multiple drive cycles. Our OBD-II scanner showed no pending codes related to exhaust leaks or oxygen sensor irregularities.

Engine performance returned to expected levels. The previously noticeable ticking sound at cold start—a telltale sign of manifold cracks—completely disappeared. Throttle response felt crisp and immediate, suggesting the new manifold was flowing exhaust gases efficiently without restrictions.

We monitored exhaust temperatures using an infrared thermometer and found even heat distribution across the manifold surface, indicating proper casting quality and consistent exhaust flow through all ports. After 500 miles of varied driving conditions including highway cruising and stop-and-go traffic, we detected no exhaust leaks, unusual noises, or declining performance.

Build Quality That Addresses Common Failure Points

Original equipment exhaust manifolds typically fail at predictable stress points—usually where the thinnest casting meets the highest heat concentration. During our inspection of the Dorman 674-870, we noticed reinforced sections at these critical junctures.

The casting thickness measures consistently throughout the manifold body, with strategic reinforcement ribs that distribute thermal stress more evenly. These design improvements address the thermal fatigue that causes manifolds to crack after years of heating and cooling cycles.

The threaded ports for oxygen sensors and studs feature clean, precise threads that accept sensors without cross-threading concerns. We tested multiple oxygen sensor installations and removals—all smooth and secure without excessive force required.