Blown Gasket between exhaust manifold and hfc

indyn

Agree with what Staples mentioned. Most likely you'll notice a burnt part on the gasket, happens on the drivers side most of the time. I've seen this with HFC and the ART pipes no matter what I used i.e. graphite crush, metallic and copper as well and that too with RTV gasket maker applied.

Apparently under high heat applications such as this, the gasket and everything around it shrink a little causing the bolts come loose a little, so most of the time its good to go back after two three heat cycles to tighten the bolts again. Thats what I did and its been holding up so far.

FYI raspy nature of cat or catless pipes is due to blown gaskets or leaks rather than the pipes itself.