It 's a style III/IV-I for a lycoming IO 320 D1B, the crack is at the junction
of the pipes coming from cylinder 1 and 2.
The tailpipes aren't tied together. This exhaust come from Snowline.
No, I don't use anything. No anti-seize (I don't know this product) and no
exhaust insulating wrap.echappement

Patrick

Patrick,

 

I have a type IV - slightly different configuration than your pictures show.  On mine, the slip joint for cyls 1 & 2 shows movement of about 1/8 th inch and was liberally coated with anti-seize before assembly.  Since I can only see the movement marks when the pipes are cold, I conclude that they are pushed together during flight conditions and if they couldn't slip that would place strain somewhere on the pipe.  However, its appears that your crack is on the top - as though the pipe was being worked up and down? 

 

Some people have supported the pipes at the firewall with an automotive type hanger and some (like me) have tied the tail pipes together with a stainless steel band squeezed in the middle.  I wonder if there is some interaction between the engine vibration, exhaust pulses, prop air pulses, loose tail pipe and the weight of the long pipe that could lead to such a crack. 

 

I did have the weld at a Y-joint crack on a new engine/pipe combination after less than 18 hours of flight, but that was caused by the #4 cylinder pipe hanging down 1 inch (for some unknown length of time) because the mechanic failed to use lock washers when the pipes were mounted.