Good compression or not - TSIO 520NB RAM VI?

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Frostyline

Filing Flight Plan
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Frostyline
Hi, Appreciate any insight! Looking at a Cessna 340A that has both Cont TSIO-520-NB engines (RAM VI 335 HP) at 130 hours SMOH by RAM. One engine has one cylinder 62/80 and rest are all above 70; another engine has four cylinders at upper 60s and two at 70s. Are those acceptable given it only has 130 hours SMOH? Thank you!
 
Generally anything over 60 is ok but right after overhaul that seems low. That said, it depends on a lot of things that you don't mention in your post. Was that cold or hot? What types of cylinders? Did you use Continentals new method etc...
 
I do not know how they did the compression test and type of cylinders they used for Overhaul. Just wondering why the compression seems low at such low hours by only looking through the log book. I am trying to buy it so don’t know this is a red flag or not before I go any further. Thank you!
 
Frostyline said:
Hi, Appreciate any insight! Looking at a Cessna 340A that has both Cont TSIO-520-NB engines (RAM VI 335 HP) at 130 hours SMOH by RAM. One engine has one cylinder 62/80 and rest are all above 70; another engine has four cylinders at upper 60s and two at 70s. Are those acceptable given it only has 130 hours SMOH? Thank you!
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Something doesn't seem right, but before I'd say it is bad, I'd like to know where the leak is.
The FAA's guidance on this is "no exhaust leaks"
 
A. Call RAM. Hear what they say.
B. If this is part of a prebuy, make sure they boroscope all cylinders. This is much better check than compression testing.
C. Make sure the test was done with the cylinders hot. A cold compression test on a Continental engine is worthless.
 
Frostyline said:
Hi, Appreciate any insight! Looking at a Cessna 340A that has both Cont TSIO-520-NB engines (RAM VI 335 HP) at 130 hours SMOH by RAM. One engine has one cylinder 62/80 and rest are all above 70; another engine has four cylinders at upper 60s and two at 70s. Are those acceptable given it only has 130 hours SMOH? Thank you!
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If I was considering a plane running 670 hp from two TSIO520s, I would go in knowing cylinder replacements were in the future.
 
Lance F said:
A. Call RAM. Hear what they say.
B. If this is part of a prebuy, make sure they boroscope all cylinders. This is much better check than compression testing.
C. Make sure the test was done with the cylinders hot. A cold compression test on a Continental engine is worthless.
Click to expand...
Agree with calling RAM, But just know, a cold compression check will catch a cylinder with morning sickness.
 
How many hours has it flown recently? From my experience, low use engine comps tent to get better with use. As long as the valves seal well, you're fine.

Borescope the cylinders, and take pics of the exhaust valve burn patterns, it means a lot more than your differential comp check numbers.

It's not rocket surgery, follow the Conti guidance on determining the serviceability of the cylinders...
 
I was once told, "Anyone who tells you that they've got a Continental with all six cylinders above 70 is lying."

So far, he's been correct. I don't think I've ever seen my IO-550's cylinders all above 70, but here I am, with nearly 2100 hours on the engine and still going.

I wouldn't worry about the compressions too much. Borescope it, and if everything turns out there and elsewhere, buy it and fly the hell out of it. But... Wait a minute, we convinced you to go with a 310 instead, right? ;) Same advice applies.
 
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