Side exhaust mounting confusion

[L88 crazy]

I bought a pair of Allen's factory replacement 2 inch side exhaust pipes for my 72. My Vette has a small block Chevy with 2 inch exhaust manifolds. I mounted them the manifold studs to the provided hole at the bottom of the doors. After a week or so I checked the pipes for looseness and they were about to fall off the car!! The manifold nuts had walked themselves loose. Did I mount the pipes wrong? What are the proper mounting points than?

 

[AdvancedAutoCC]

I bought a pair of Allen's factory replacement 2 inch side exhaust pipes for my 72. My Vette has a small block Chevy with 2 inch exhaust manifolds. I mounted them the manifold studs to the provided hole at the bottom of the doors. After a week or so I checked the pipes for looseness and they were about to fall off the car!! The manifold nuts had walked themselves loose. Did I mount the pipes wrong? What are the proper mounting points than?

Any time you do exhaust work, you need to retighten any fasteners after several heating and cooling cycles, this is especially important with header bolts. Manifold flange nuts will relax tension after several cycles. Brass nuts in particular are prone to this.