Do I need to clean the mating surfaces before installing this gasket?

Yes. Scrape away old gasket material and carbon buildup from both the header and cylinder head surfaces. Clean metal-to-metal contact ensures the seal holds under heat and pressure.

Will this gasket work with an aftermarket header?

Aftermarket headers may use different bolt patterns or mounting geometry — verify the bolt hole spacing and surface finish match this gasket before purchase.

What torque spec should I use when bolting down the header?

Refer to your vehicle's service manual for the correct fastener torque. Over-tightening can warp the gasket; under-tightening causes leaks.