First, make sure you have the correct sized muffler inserts for your application. Sanderson 1.875" inserts are for small block engine applications, and the 2.250" inserts are for big block engine applications.

For NEW installations - Notice that one end of each Sanderson muffler insert is partly closed off with a welded washer. Insert the muffler into one of the pipes of the header with the closed-off end first. Drill a hole through the bottom of the header pipe which will also go through the wall of the muffler. Insert a bolt through that hole and tighten it with the nut on the inside. (Some customers have used sheet metal screws to hold the mufflers in place, but such screws tend to quickly vibrate loose.) When the mufflers are securely fitted in all eight pipes, the headers are ready to put on the engine.

Sanderson Headers does NOT provide holes for mounting the muffler inserts due to possible liability issues. Safe installation and proper securing of the insert is the responsibility of the customer or installer.