SS Headers on LS400

[Lextreme II]

Anyone with a first generation LS400 with SS headers? If yes, does the stock cats fit perfectly or you have to modify the cats in order to make them work?

 

[JBrady]

David the stock cats will NOT fit without modification. The 3 bolt header outlet flange is not the same size as earlier cars.(pre 1998)

Also, since the headers are longer than the early manifolds the cats will be moved farther back and lower than stock. You could possibly have a shop modify the cats to fit or relocate them under the car.

 

[Lextreme II]

I am asking because i have my turbo cross pipe attach to the passenger side stock header and would like to change the passenger side to increase flow.

 

[JBrady]

I am asking because i have my turbo cross pipe attach to the passenger side stock header and would like to change the passenger side to increase flow.

You would need to use a late model 3 bolt flange (available from S&S), shorten your downpipe 1-2" and weld the flange on in the correct position.