Guess the failure?

[GraemeSmith]

#1 EGT has blown out of the pipe

Dammit Murray! And on my last flight - it did! Exhaust streaming into negative pressure area and getting drawn into air intake - rough engine resulting and no EGT 1.

Seriously....

No 3 was ready to let go too.

560 hours on the pipes which remain in excellent shape under the exhaust wrap.

Just replaced them all. It's only money........ :-)

[Murray Parr]

#1 EGT has blown out of the pipe

Dammit Murray! And on my last flight - it did! Exhaust streaming into negative pressure area and getting drawn into air intake - rough engine resulting and no EGT 1.

Seriously....

I tried to warn you! lol

All jokes aside, is it possible you had a restriction causing excess back pressure given the gasket blew out prior to this?

[GraemeSmith]

Restriction. Pretty sure no. Even the birds round here don't try and build nests in tail pipes! Though they try everywhere else.

Probe failure - flat out old age

[Murray Parr]

The gasket might have blown due to warped flange (Can happen from over tightening or just too many times tightening it). Run a straight edge across the flange will determine if this is so, you can also set the flages to be slightly concave so when the nuts tighten, it returns to flat.