Clanking noise from exhaust

[Bigb55]

I have a 1974 K5 with a 350 and sm465. Recently it has started making a clanking noise that emanates from the rear of the exhaust. Heard at idle, it's a pretty rythmic tap but hard to tell if it speeds up with throttle.

The sound can not be heard near the engine bay (other then hearing it from where the exhaust exit is). Sounds similar to a bearing going out but can't hear it at the pan. Can't hear it at the heads either.

I checked the timing and adjusted it to ~10° BTDC from ~16° BTDC. It certainly runs better not. But clank is still there. Figured it might be misfiring.

Also the clutch shudders when decelerating and in neutral. Like coming to a stop. Clutch holds gear and doesn't slip or shudder in gear. It started around same time as the clank sound started. Could the flywheel or clutch be going out and causing it? Or just a coincidence? Could a muffler gone kaput?

Any ideas where to look? So I don't end up tearing apart the whole engine?

Or use it for an excuse to get a new crate engine?

 

[rampage]

Sounds similar to a bearing going out ...

Probably a muffler bearing that dried up from lack of grease. Or maybe loose exhaust flange bolts or internals of the catalytic converter/exhaust broke loose. Use the end of a cut off broom stick or similar wooden dowel. Hold one end to your ear and press the other points along the muffler system to see where it’s loudest. Any chance you could post up a video of it making that noise?

 

[Bigb55]

Probably a muffler bearing that dried up from lack of grease. Or maybe loose exhaust flange bolts or internals of the catalytic converter/exhaust broke loose. Use the end of a cut off broom stick or similar wooden dowel. Hold one end to your ear and press the other points along the muffler system to see where it’s loudest. Any chance you could post up a video of it making that noise?

Ha muffler bearing good one.

Checked header bolts and other exhaust parts for loseness. All tight. And it's pre cats so doesn't have them.

Could something in the heads be loose and getting amplified by the exhaust? Where it would be quiet at the heads but noticeable at exhaust ?

I'll try and get a video of the sound.

 

[diesel4me]

Muffler baffles can break loose and make rattles,clunks,and other disturbing noises...some double walled exhaust pipes make weird noises as the two pipes expand & contract too..so can a catalitic converter with the catalyst broken loose..

Maybe some mice are nesting in the muffler--seen some cars with mufflers packed full of shelled nuts,acorns,and other things before at my friends shop..one car that sat only a month had to be towed to his shop,it started,but stalled almost immediately and refused to start again..he suspected a clogged converter,but it was the muffler..

It may be the clutch causing the noise and its being amplified by the exhaust..I've had 3 finger pressure plates have one or more finger screw up and become loose,and they rattled and made for chattering starts until it finally refused to disengage..after having 3 of the 12" three finger type pressure plates fail rapidly,I switched to a diaphragm type ,the pedal effort was so much less I wished I'd done that right away..depressing the pedal with a 3 finger type is about the same as using a universal gym with 100 lbs of weight on it with your left leg..

 

[dyeager535]

Without hearing it, impossible for me to put the sound you are describing to a particular cause, but have you made sure your exhaust is solid?

It's a tight squeeze getting the pipe(s) over the axle and around the tank, with a poor install, cheap or worn out mounts, the exhaust can move around enough to contact various parts of metal towards the back...frame, gas tank, gas tank skid plate if equipped. Further forward, it can rub on the crossmember if run over the top of it.

 

[TJ1978]

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