Exhaust question
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Joined: May 2002
Posts: 59
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From: IN
Exhaust question
My 86 Iroc (305 tpi) had a rotting y-pipe, it was really getting bad to drive, fumes coming in the car, sounded like crap. So I changed the y-pipe and now I have an exhaust leak on the passenger side. It sounds bad when the engine is cold but goes away when it is warm, with hood up I can see the initial exhaust blast come up out of the passenger side of the engine bay. When I changed the pipe there was a cast iron spacer block sandwiched inbetween the manifold and pipe. Is there supposed to be a gasket there? I could have sworn the manifold and and spacer had flat mating surfaces and no gasket (never found one anyway when I took it apart) and the pipe side had the normal bevel surface. I may have had this problem with the old y-pipe and never knew it, it had holes everywhere noises couldn't be pinpointed 
Supreme Member
Joined: Mar 2000
Posts: 13,414
Likes: 6
From: Central NJ, USA
Car: 1986 Firebird
Engine: 2.8 V6
Transmission: 700R4
Sounds like my 2.8's y-pipe, with the gasketless flange. Was yours angled to fit inside the y-pipe end, and flat for the manifold end? If so, there shouldn't be a gasket, try retigtening the bolts.
As a side note, I found a performance benefit by hogging out the center of those cast iron donuts. Mine had a step in it, where it looks like GM's boring machine might've done some work. I smoothed the step out, and thought "hell with it", and widened it out some more. I could definately feel an improvement with the go-pedal. I used a round metal file for the initial work, then a stone in a die grinder to polish up the inside. I tried to take pictures, but they came out like crap...
You could also check that side's donut to make sure the exhaust mating edge is completely flat, same with the manifold output.
I've had the driver's side loosen up a few times (I'm too scared to crank the nut on), and it's the same symptoms you just described. 'Fact, when this happens, if the motor's cold, I can actually slide the donut around with my finger. Good thing it hasn't fallen out yet!
Last time, I let the flange vibrate loose for so long, that it wore down the lower manifold-to-y-pipe bolt. I'd tighten the nut, then it'd loosen, then it'd get tight...after a minute or so, I removed the nut altogether, and felt the stud threads. They were worn down! So I stacked some washers on the stud, and CRANKED the nut down. Lets see if it moves now! I wonder if the same thing happened to your manifold stud threads.
As a side note, I found a performance benefit by hogging out the center of those cast iron donuts. Mine had a step in it, where it looks like GM's boring machine might've done some work. I smoothed the step out, and thought "hell with it", and widened it out some more. I could definately feel an improvement with the go-pedal. I used a round metal file for the initial work, then a stone in a die grinder to polish up the inside. I tried to take pictures, but they came out like crap...
You could also check that side's donut to make sure the exhaust mating edge is completely flat, same with the manifold output.
I've had the driver's side loosen up a few times (I'm too scared to crank the nut on), and it's the same symptoms you just described. 'Fact, when this happens, if the motor's cold, I can actually slide the donut around with my finger. Good thing it hasn't fallen out yet!
Last time, I let the flange vibrate loose for so long, that it wore down the lower manifold-to-y-pipe bolt. I'd tighten the nut, then it'd loosen, then it'd get tight...after a minute or so, I removed the nut altogether, and felt the stud threads. They were worn down! So I stacked some washers on the stud, and CRANKED the nut down. Lets see if it moves now! I wonder if the same thing happened to your manifold stud threads. 
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