W Body Store

Downpipes - What you want to know

A few years ago the only downpipe on the market for your GM 3800 vehicle was the unit made by R/T. Fast forward to today and there are a slew of downpipes available for your car. So what's right? What's good? What should you look for when shopping for a downpipe? We're going to cover that in this technical writeup. Fasten your seatbelt; you're about to become a downpipe expert.

Bore Dimension

The main restriction in the stock downpipe is it's inner diameter. Shortly after the flange the stock downpipe goes down to a 2.1" inner diameter pipe. A pipe this size is not optimal for the best airflow on a supercharged motor and isn't even considered acceptable for the naturally aspirated motors. So what should you look out for? Well, if going for optimal flow look for the downpipe with the largest bore. It might interest you to know that none of the pipes currently on the market are a true 3 inches in diameter, so you'll want to look for the pipe with the largest inner diameter closest to 3 inches. As seen in the picture below W Body Store's 3" downpipe measures 2.88" in diameter, the largest on the market at the time this article was written.

Large downpipe

Weld Quality

Something that seems so meaningless is actually one of the most important details to consider on your downpipe. When purchasing a downpipe from anyone, ask for a picture of their weld work. Sloppy welds seem to be the norm rather than the exception. We've noted that most of the pipes on the market actually have pinhole leaks in them. Running a competitor's downpipe? Look under your car around the downpipe's welds for black streaks. These streaks are leaks where exhaust has leaked from the pipe and carbon deposits have formed. We found upwards of 20 leaks on one of the best selling pipes in the market! We pride ourselves in the quality that goes into each W Body Store Downpipe. A picture of our weld work can be seen here.

Weld Job

Flexpipe Length

This is a very important detail to note also. Some pipes on the market utilize 2" long flexpipe portions. While using a shorter flexpipe will save money, it will not stand the test of time when connected to a motor making, in some cases, upwards of 400 ft/lbs of torque. Look for a pipe that uses a 4" long flex piece. W Body Store gives you a 4" long flex pipe standard. Only the highest quality components are used in our downpipes.

Downpipe Material

Don't let anyone convince you that stainless steel is the only acceptable material a downpipe can be made of. This is a marketing ploy. Stainless steel, while a great addition to any pipe, is not required due to the heat that the pipe sees. The heat wards off any condensation and therefore any material, even mild steel, should last the lifetime of the car. With that said, all of our pipes are constructed of Stainless Steel.

T409 vs. T304 Stainless Steel - Our competition keeps touting how great their choice of material is when it just doesn't matter. Both T304 and T409 will never rust through and the only difference between the material is one will be shinier than the other though both will be covered in road grime and not visible to the user!

Catalytic Converter

Yet another important detail, some of our competitors are using generic catalytic converters for their downpipes. W Body Store uses ONLY Magnaflow High Flow Catalytic converters.


There you have it... You're now an expert on downpipes! Go share your new found knowledge with the world. Now you can see why we've sold more downpipes than any other 3800 specific vendor and why our downpipes are often regarded as the best. Like all of the products we offer, we pride ourselves on using nothing but the best components and the best vendors. We're confident that you will love your 3 inch downpipe and if you don't we'll take it back!