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Failed Exhaust Valve Seat

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Failed Exhaust Valve Seat

Postby davehw » Wed Jul 11, 2018 11:20 pm

:o Hello Jabiru owners and users.
Have just joined this group, and wondering if anyone has had an exhaust or inlet valve seat come loose?
Being a L2 and L4 with the RAA, I have just come across this happening in a J120 with 600 hours on engine/airframe. BUT NEW VALVES FITTED 22 HOURS AGO !!!
2 photos attached. cheers, Dave.
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Re: Failed Exhaust Valve Seat

Postby diablo » Thu Jul 12, 2018 3:02 pm

Hi

yes there have been reports of valves guides dropping and they seem to be relating to engines that are running hot with high CHTs. It is something to look out for on all Jabiru powered aircraft. Engines that continuously with very high CHTs (training or aircraft with inadequate cooling) eventually fail due to continuous cycles of expansion and contraction of aluminium.

Best steps that can be taken to stop it happening is :

1. Ensure tappets are correctly adjusted at specified intervals
2. When climbing, increase speed and airflow be reducing angle of climb
3. Monitor all CHTs

To improve Cylinder Head cooling, look at the tips and improvements that have been posted on this website under engines. The changes and improvements to airflow, really work !
Sent from my "Electronic Numerical Integrator And Calculator" E-N-I-A-C
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