I recently bought a 68 Firebird 400 4 speed convertible with dual exhaust. Its my first classic. Love love love the car. Its a driver and has issues but hope to improve things while I enjoy having it.

Right now my biggest problem is the driver side muffler rattles like crazy. It has 'sonic turbo' mufflers. When i first start the car cold it rattles like something is gonna fall off. If i reach under the car, grab the muffler with my hand and squueze the metal halves together the top half of the muffler 'pops' down and the rattling to stops. As soon as i let go the top half pops back up and rattles.

When the muffler is hot it rattles less but it is still noticeable. NOT the kind of noise a classic should make. How can i fix this? The exhaust is fairly new but should I get a new muffler? (after googling sonic turbo mufflers maybe they just look new, they haven't been built for decades)

Thanks for any help in my Firebird journey!

Welcome,

You probably need to tighten up the clamp that goes over the pipe unless you don't have one on there.

Probable a bad muffler that has given away on the inside. Probable the only fix is to replace it.

Sounds like the internal baffles are burned loose. New muffler or in the meantime, Take muffler off and shake out whatever is loose inside, or get a large hose clamp and clamp a piece of metal to the top of the muffler, tighten it until the top oil-cans down on the loose baffle to quite things down until new muffler purchased.

Pipes on a convert have very little clearance between the tunnel and the reinforcement pan. Even the slightest misalignment of the system from manifold to crossover will cause a terrible rattle.

Thanks everyone! I thought new mufflers might be in the future. For now a tuna can and a large hose clamp have quieted the rattle.