Head porosity found during annual

[Guest]

23 hours ago, Pinecone said:

Agreed.

But porosity is not a crack.  Yet.

The simplest way to determine the condition is to drop the exhaust then dribble a little LPS#1 down the head between the fins, the look inside the exhaust port.  The LPS on the carbon in the port acts exactly like dye penetrant.  I’d bet that it’s cracked.

[Yourpilotincommand]

Nice compressions. Did a borescope reveal any cracks?  Then… I would consider replacing only the cracked cylinder.  I shall assume we all now have borescopes. Definitely get Savvy subscription. I’m sure the first question they ask… what did the borescope say?

btw… my girlfriend went to get an oil change at the dealership the other day. They told her the transfer case needed seals and the brake rotors are worn out for $3k. She declined. I crawled under and didn’t find a single leak.. bone dry, and the rotors looked almost new.

[PT20J]

I

15 hours ago, M20Doc said:

The simplest way to determine the condition is to drop the exhaust then dribble a little LPS#1 down the head between the fins, the look inside the exhaust port.  The LPS on the carbon in the port acts exactly like dye penetrant.  I’d bet that it’s cracked.

That’s a good trick. I’m betting on cracks also. I researched aluminum casting porosity and found that it is a known manufacturing defect caused by gas bubbles in the molten aluminum during the casting process. BUT, it only causes tiny voids that don’t really affect anything. They show up as minor surface pits when a casting is machined. The voids are not numerous or large enough to form a channel all the way through the metal. 

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[Jsno]

I would replace the cylinders.  Compression check is only part of the puzzle when evaluating cylinders, not the only determination of their health.  The way I look at is is when you are flying at night, hear a loud bang, then silence, the price of new cylinders will quickly not matter.