To Header or Not to Header

A high-performance car needs custom headers, right? Not so fast. When I asked my engine builder, Brian Thompson, about custom headers he said that he could make me a set and take my money, but that there would be absolutely zero performance improvement. The LS7 manifold is well engineered and has individual hydro-formed tubes inside as shown above. He's aware that some people have made gains when they switched to custom headers, but that was because they changed something else (i.e., removed the cats). He's done lots of R&D for GM on LS motors and he knows what he's talking about. So going with headers provides no performance gain and you will have more heat and less space. The LS7 manifolds look really nice ceramic coated and that's my plan...

The biggest challenge in using the manifold is that it has a funky flange. While there are aftermarket ones available, they lack the recess to properly squeeze/retain the gasket. So I bought a set from Ken, another SL-C builder, who cut them from a set of catalytic converter pipes left over when an owner of a very low-mileage C6 Corvette Z06 upgraded to custom headers (sucker!). 

Qty. Part Number Description Unit Price
1    LS7 Exhaust Flange (Custom Modified) $140.00
2  15272179  GM Exhaust Manifold Gasket  $20.88
1   Cermaic coat LS7 Exhaust Manifolds  
1   Apply HeaderShield to LS7 Exhaust Manifolds $1,268.00
2   TBD Mufflers  
2   TBD Catalytic Converter  

How Ken makes his exhaust 

How Mark makes his exhaust 

Peter's exhaust

 My friend Peter's exhaust sounds great! Some notes:

  • LS7 manifolds

  • Corvette catalytic converters

  • 3" pipes

  • Mufflers used to be called "hushpower DBX" but rebranded to Flowmaster DBX; webpage here

  • Simple setup, pipes start at the LS7 flange and are welded to the cats, from the cats there is a connection to a bit of pipe, welded to each muffler. The mufflers are then joined by a pipe at the muffler outlets to a center oval exhaust pipe.

  • Very easy to take on/off, effectively it is 3 pieces after the manifolds, the right / left pipes/cat assemblies and then the two mufflers/exhaust pipe. He was even able to get my transaxle in/out without taking any of the exhaust out.

  • Oval piece is custom made.

Exhaust Tips



  • Pan to Bottom of Chassis: 2-3/8”

  • Transaxle Rear to Bottom of Chassis:

  • Oval Tubing: 2.5” oval

    • Race Mufflers 3”: 2-1/8” x 3 ½”

    • Pro Fabrication NC ?

    • Spin Tech

    • Vibrant Performance