Peterbilt 387 Exhaust Parts

Frequently Asked Questions About Peterbilt 387 Exhaust Parts

What exhaust stack sizes fit the Peterbilt 387, and how do I measure for the right diameter?

The Peterbilt 387 typically accommodates 5-inch or 6-inch diameter exhaust stacks, though some models can handle 7-inch with modifications. To measure correctly, check your existing exhaust pipe's outer diameter at the connection point, not the stack opening. Most 387s from 2000-2010 came standard with 5-inch systems. If upgrading from 5-inch to 6-inch, you'll need new clamps and possibly a reducer, depending on your turbo outlet size.

Will aftermarket exhaust parts void my warranty or affect emissions compliance?

Aftermarket exhaust components downstream of the DPF/muffler (like stacks and tips) won't affect emissions compliance or void powertrain warranties. However, replacing or modifying components before the DPF, including flex pipes or Y-pipes on 2007+ models with emissions equipment, may impact compliance. For pre-2007 387s without DPF systems, you have more flexibility. Always verify your state's specific requirements and keep original parts if you need to return to stock for inspections.

What's the difference between aluminized and chrome exhaust parts for longevity?

Aluminized steel parts typically last 3-5 years in normal conditions and cost about 40% less than chrome. They develop a matte gray appearance over time but maintain structural integrity. Chrome parts can last 7-10 years with proper care but require regular polishing to prevent pitting and rust spots, especially in winter climates with road salt. For best durability in harsh conditions, consider 304 stainless steel options, which outlast both but cost more upfront.

Do I need special brackets or modifications to install curved exhaust stacks on my 387?

Most curved stacks for the 387 use the same mounting points as straight stacks, but you'll need to verify clearance from the cab and sleeper. Curved stacks typically require 8-12 inches of clearance behind the cab. Some installations need extended brackets (usually 6-8 inches) to position the curve properly. Check that your existing exhaust hangers can support the additional leverage from curved stacks, as they put more stress on mounting points than straight pipes.

Why do my exhaust clamps keep loosening, and what's the proper installation torque?

Loose clamps usually result from under-torquing, thermal cycling, or using wrong-sized clamps. For 5-inch systems, torque band clamps to 60-80 ft-lbs; for 6-inch, use 80-100 ft-lbs. Always use new clamps when installing parts - reused clamps lose tension. Apply high-temp anti-seize to threads and retorque after the first 500 miles when parts have heat-cycled. Preformed clamps work better than flat bands for maintaining consistent pressure on Peterbilt 387 applications.