Aztex_Slingshot
Carlisle, NY
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I thought for sure the issue was piston slap, because it sounded just like the noise my last GMC made which was diagnosed with the dreaded slap. It turns out that the noise is from a broken stud on the passenger side exhaust manifold. Does anyone know what could cause that to happen? It seems to me that perhaps they were over torqued at the factory, but I'm certainly not a mechanic. So the dealer gave me a "quote" of between $400-$500, and that's if the stud comes out, otherwise the head will have to be removed and taken to a machine shop...ouch!
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Gale Hawkins
Murray, KY
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The 454 version of the engine warped exhaust manifolds and if you have done much hard pulling at slower speeds they have gotten hot I am sure. In the MH it was typically a 50K+ mileage experience. The big block Fords were the same.
Not sure I would take this to a lot of dealers. A local exhaust shop that may be even staffed by the owner may have much higher skills of this issue. My shop was able to weld a nut on the stud and back it out then had both exhaust manifolds milled back into specs.
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ib516
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My 2001 Chevy Venture had 3 broken exhaust manifold bolts I had to fix. Thankfully, they were all on the front side of the engine, but it was still a pain.
Nothing really "causes" it to happen, other than inferior quality or undersized bolts/studs. The heat and cool cycles cause stretching and contracting and that eventually causes a failure with cheap parts.
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msjdbman
SW Michigan
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Many times, the back pressure of a restricted exhaust system causes excessive heat build up in the manifolds and stud/bolts, especially in tow vehicles where there is extended periods of heavy loads. It is surprising how just a muffler that allows better flow can reduce this significantly. Another helpful trick is allowing the engine to idle for a few minutes prior to shutdown. It helps dissipate the heat that has accumulated in the manifolds so that there is less expansion/contraction of the studs/bolts.
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superdutyjayco
Central Ohio
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Gale Hawkins hit the problem on the head. I've worked on many small and big block chevies in motorhomes and trucks pulling big loads. You should try putting one of those manifolds back on. The manifold actually contracts between the exhaust ports when they cool down. A quality set of headers is a good option, and generally less money than replacement stock exhaust manifolds.
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Ron3rd
Upland, CA USA
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Gale Hawkins wrote:The 454 version of the engine warped exhaust manifolds and if you have done much hard pulling at slower speeds they have gotten hot I am sure. In the MH it was typically a 50K+ mileage experience. The big block Fords were the same.
Not sure I would take this to a lot of dealers. A local exhaust shop that may be even staffed by the owner may have much higher skills of this issue. My shop was able to weld a nut on the stud and back it out then had both exhaust manifolds milled back into specs.
"Not sure I would take this to a lot of dealers. A local exhaust shop that may be even staffed by the owner may have much higher skills of this issue."
Excellent advice. DO NOT TAKE IT TO THE DEALER. A good exhaust shop will fix you up in no time.
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retento
Rocky Mount N.C.
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I have been telling folks to check their exhaust manifold bolts for months... I had one missing on the left fron of my 2001 8.1. Friend of mine thought he had the dredded piston slap until he tightened his manifold bolts... Piston slap disappeared, go figure!!! No suprise why they break.... Could they have those manifold bolts any smaller...? Little metric POS bolts.......
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JJBrown
Whitby, Ontario, Canada
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Just had the dealer fix a broken stud on my 05 Denali under warranty.
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Perrysburg Dodgeboy
Perrysburg, Ohio USA
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Not sure why you would say not to take it to a dealer other then cost, but I'm sure the guy at the dealer can handle removing a busted bolt just as well as any exhaust shop. And if the head needs to be removed I think the dealer may be better at that then an muffler shop.
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Gale Hawkins
Murray, KY
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Perrysburg Dodgeboy wrote:Not sure why you would say not to take it to a dealer other then cost, but I'm sure the guy at the dealer can handle removing a busted bolt just as well as any exhaust shop. And if the head needs to be removed I think the dealer may be better at that then an muffler shop.
Don
Don muffler shops should not have to remove the head due to higher skills. Dealerships are part swappers in many cases. 
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