Joe;

 

Thanks for info.  When the crack occurred last Feb, where was that – also at the header to muffler tube weld?  I expect that to be the worst stress point because of the axial expansion of the muffler being greater than that of the engine between the ports.  BTW; do you have the stock exhaust gaskets on there?

 

My setup is similar, and potentially worse because it looks like the headers are shorter, and the dimensional change from rotor 1 to rotor 3 will be greater due to the longer length (photo).  I have a SS baffle over the exhaust in a similar manner as yours (photo).

 

My engine/exhaust has about 12-14 hours on it; dyno runs plus on the plane testing, and no cracks at this point.  Lots of full power cycles on the dyno, some up to 7000 rpm. 

 

I think the design has too many welds/joints subject to thermal and mechanical stress which Inconel, being brittle,  cannot handle

I don’t know that inconel can be considered brittle, it bends and stretches.  It is very strong, has good high temp strength, is very corrosion resistant; and considered to have good fatigue resistance, which increases as temperature is increased.  Its behavior is dependant on heat treatment (and of course which alloy – 600, 718 or 800).  Unfortunately we don’t know what we have, nor what sort of post weld treatment it received.

 

I’m very interested in seeing your new design when you’re ready to show us that.  I’m guessing the probability is quite high that I will be doing something else at some point.

 

Al