Anyone know how to inspect cam lobes in an O-320 (E2A) without pulling a jug?

[Robert Rice]

Want to buy a low time yet very old Cherokee with few hours over years. Owner will not let me pull a jug to inspect.
Does anyone know of a way to inspect for cam/lifter spalling without pulling a cylinder?

 

[455 Bravo Uniform]

Remove and cut oil filter, if it has more than 10 or so hours on it. If not, is it airworthy to be flown a lot, then check?

Oil lab test? Though you may have nothing to compare to, and it may not be foolproof indicative.

Perhaps insert borescope in the oil fill? Some engines this works. I can see a couple cam lobes on my Continental IO-470. (From the oil drain perhaps?)

That’s all I can come up with.

 

[Dan Thomas]

Lycs are hard to examine without removing a cylinder. The bottom of the crankcase makes inspection via the oil drain nearly impossible. The O-320's oil filler goes into the sump, not the crankcase where all the moving stuff is.
Pull a magneto. If the gears in there have rust stains, it's a bad deal. The same blowby moisture that corrodes gears and cylinder walls is the same moisture that starts cam and lifter damage.

If the owner has been ground-running it without flying it, I plan on an immediate engine replacement, and offer accordingly.

 

[Racerx]

Got a feeling the same owner that won't let you pull a jug probably won't let you pull a mag.

Where it based? I'd walk or price it accordingly.

 

[Llewtrah381]

My A&P "examined" mine on my O-360 by pulling off the valve covers and measuring how high up the pushrods came (or something similar). I think it provided a relative comparison rather than an absolute one; it showed one lobe was 0.030" shorter than the others. Then again, it may have been total travel distance and been absolute. It's not a direct visualization but it was an assessment that was simple to do. I'm not an A&P, so I may have the exact technique wrong. It set me back an hour of shop labor plus $8.50 for gaskets.

This wasn't specifically to check for spalling but it could help (I had some increased iron in oil analyses but no metal on filters).

 

[NavAir]

Got a feeling the same owner that won't let you pull a jug probably won't let you pull a mag.

Where it based? I'd walk or price it accordingly.

Really? I wouldn't allow anyone to pull a cylinder on my engine, much less a prospective buyer (unless there was an issue with it). Magnetos, no problem pulling one (or both). I agree with checking oil analysis data, cutting the oil filter,run history, etc.

 

[Robert Rice]

Got a feeling the same owner that won't let you pull a jug probably won't let you pull a mag.

Where it based? I'd walk or price it accordingly.

It is priced accordingly - so maybe I pays my money and takes my chances...

 

[Robert Rice]

Really? I wouldn't allow anyone to pull a cylinder on my engine, much less a prospective buyer (unless there was an issue with it). Magnetos, no problem pulling one (or both). I agree with checking oil analysis data, cutting the oil filter,run history, etc.

Based in Kokomo, previously Minnesota. I'll ask Mx to pull a magneto and look for rust - bore scope the cylinders and hope for the best.

 

[Robert Rice]

Remove and cut oil filter, if it has more than 10 or so hours on it. If not, is it airworthy to be flown a lot, then check?

Oil lab test? Though you may have nothing to compare to, and it may not be foolproof indicative.

Perhaps insert borescope in the oil fill? Some engines this works. I can see a couple cam lobes on my Continental IO-470. (From the oil drain perhaps?)

That’s all I can come up with.

Its been getting yearly oil analysis - I'll check with blackstone but according to the original Mx they have been normal (he has no stake in this bird). Borescope - yes good idea. and pull a mag and look around.

 

[bbchien]

Does the AC have a good panel?
That’s the only thing that might make it worth an engine with that history. What you also want to see are the MAINS.

 

[Robert Rice]

Does the AC have a good panel?
That’s the only thing that might make it worth an engine with that history. What you also want to see are the MAINS.

No, just a descent paint job and interior PA-28 at a low price and low hours. I may need to spend more money on it down the road.

 

[Magman]

Last week I just did the 500 Hour Mag Service belonging to a Cherokee 140.

I had done the previous one as well during “ The Project ”.

When I first met the aircraft it had not flown in over 20 years.

It was up on JACKS! Not for Mx; but for the times the nearby river would

( not IF) flood! All cylinders were removed and the Cam looked good

with no internal rust. Since then it has flown 500 hrs over about a 10 year

period with no issues. Ya never know.


A couple clues as to Cam condition follow:

Does it make Minimum Static RPM as verified with a hand held Tach?

If not the aircraft is Not Airworthy pending further diagnosis.


Another crude check of the condition is to check Dry Lifter Clearance.

An accurate assessment requires extensive disassembly but you can see

if in the ball park by Rocker Cover removal only. It takes about 1 hour to do.


Turn prop and observe valve open fully. Let it sit for several minutes to

allow the Lifter to bleed down.

While keeping pressure on Rocker Arm against Pushrod rotate prop till

valve closes and cylinder is at TDC. Check clearance at valve end of

rocker arm. Do not release pressure until check is completed. It is crude

and might give you a false positive but if clearance is excessive then

a bad lobe is suspect.


This is predicated on the engine being properly assembled in the first place.

There are folks that are not aware of or ignore Dry Lifter Clearance. If they

put it together don’t walk away. Run!