Those of us with Cummins QSM11 engines are all too familiar with exhaust leaks at the manifold to cylinder head interface. Everything we read about it centers around running the engines at the wrong fuel consumption / load range. We typically take pitch out of the propellers to reduce load and fuel in the desired operating ranges which lowers the exhaust gas temperatures. That and change the manifold gaskets and bolts should fix the problem right? Not so fast..... As it ends up all that heat can warp the mating face of the manifold then exhaust erosion can further degrade the surface. So, in the first picture the manifold is trued in the mill and an indexing cut of 0.002 inch was run over the surface with a fly cutter. You can see where the cutter did not touch the material at the end of the manifold. For this part of the manifold a total of 0.025 inch was removed for proper sealing (second picture). The second half, obviously needs the same amount cut off but it also had significant warpage.
So, don't assume that changing gaskets and bolts will correct the exhaust leaks; if you are going to all the effort, get the manifolds machined....
Tom
So, don't assume that changing gaskets and bolts will correct the exhaust leaks; if you are going to all the effort, get the manifolds machined....
Tom
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