87 350 tbi exhaust chirp

[Sam71395]

Do you still have the factory manifolds? Is the air injection system still intact? Could it be related to that somehow?

Sometimes the internal baffles in a muffler will break the tack welds and move around. Could your noise be a metal to metal rubbing inside the muffler(s)?

I do still have the factory manifolds, smog equipment was removed by previous owner. the best way I can describe the noise is a chirp, the only time I have heard somthing close to it is one time I had a small engine with a bad head gasket and when it would run some compression would escape past the head gasket and it would sound very similar to what I'm hearing now

 

[82sbshortbed]

A video would help maybe. If it will pick it up.

 

[squaredeal91]

Could be an intake manifold gasket Sucking air in the valley?? If it were a Diesel it would have runaway lol.

 

[Sam71395]

Could be an intake manifold gasket Sucking air in the valley?? If it were a Diesel it would have runaway lol.

theres a thought, this truck sat for about 8-9 years prior to me owning it, maybe those could have dried out, is there a way to check for this?

 

[Rusty Nail]

out on it in
Whew!

Im voting for transmission cooler line rub.

 

[Sam71395]

THE CULPRIT HAS BEEN FOUND the holes in the manifold from the smog pump still had the fasteners in them with the holes in the middle welded closed, I'm assuming the exiting exhaust gasses whistling over them was causing my sound, similar to how you can blow over the top of a pop bottle and the bottle whistles. replaced them with normal bolts and the chirp is gone completely

 

[Rusty Nail]

That is the same thread as a Cummins oil pan drain plug I'm thinkin.

 

[Sam71395]

That is the same thread as a Cummins oil pan drain plug I'm thinkin.

possibly, I'm not sure, just found a couple of bolts layin around and put them in

 

[Redfish]

THE CULPRIT HAS BEEN FOUND the holes in the manifold from the smog pump still had the fasteners in them with the holes in the middle welded closed, I'm assuming the exiting exhaust gasses whistling over them was causing my sound, similar to how you can blow over the top of a pop bottle and the bottle whistles. replaced them with normal bolts and the chirp is gone completely

That's why I asked about the manifolds in post #14. @bucket posted something about it a while back on his 454SS thread.

Mine was getting air in through part of the old smog system and causing me some backfiring issues.

Glad you found it and got it resolved.

 

[RecklessWOT]

Could be an intake manifold gasket Sucking air in the valley?? If it were a Diesel it would have runaway lol.

lol a bad enough intake leak can cause basically a "runaway" on a gas engine too. Lucky my truck is TBI, it sucks WOT when you start it because of a bad intake gasket that was neglected since before I bought it and finally just let go completely, but luckily it can't get fuel once you shut it off...

 

[TerryRH]

Wish I'd have seen this sooner. I have the same chirp, and recently found it was a bad intake gasket.