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Discussion Starter #1
So, for a while now, after I had my engine rebuilt with 10:1 pistons, I had a ping at low engine load. This lasts until the motor has been running for about 45mins to an hour, then it goes away. It also pops and burbles on decel, which isn't a bad sounding thing, but it isn't a Lambo I realize :wink2:

I also had exhaust fumes in the cab that is annoying when the hard top is on. Today I found that I could feel exhaust pulses from the manifold to down pipe connection, so I tightened things up. The inner two bolts were a little loose. Well, it still pings but it's barely perceptable, and it stops much sooner, about 20minutes. And no more popping on decel when shifting gears.

It's almost like I found a vacuum leak and fixed it. Is an exhaust leak close to the engine a bad thing in that respect? Did it cause a lean or rich condition, causing the pinging and exhaust popping?
 

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But Mad North-Northwest
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That’s upstream of the oxygen sensor, so a leak there will mess up your mixture, yes.

I would replace the gaskets and retighten: it’s not very hard to do in-situ assuming the bolts aren’t rusted in place.
 

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Discussion Starter #3
That makes sense, thank you! The gasket was replaced last year, as I had wanted to get rid of the exhaust leak. I had to take it to a muffler shop since one of the bolts was spinning in the manifold. I think that it loosened up, or they didn't get it tightened enough; they did all of the work on a lift while I waited. This was a pretty decent looking gasket; in case one of the flanges are warped, I wonder if I could double up the gaskets?
 

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But Mad North-Northwest
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Pretty sure I used brass nuts there. They don’t loosen with heat cycling.
 

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Discussion Starter #5
Well, they loosened up again. I'm irritated with this; that one corner close to the engine has failed 2x where the stud starts to spin. I'm hoping that this isn't the case again. I could still feel a puff of exhaust a few moments before it became too hot to keep my hand there.
 

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Discussion Starter #7
Yeah, here's a photo of an S3 on top with studs.

I'm still thinking of doubling up on the exhaust gasket if the stud turns out to be solid. And finding brass nuts...
 

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