0300A - inspecting lifters?

[rmorton]

I'm a new 170B owner (1955 with 0300A). It sat for 15 years in Missouri before I bought it this past summer. I'm slowly going through everything I can before it gets a thorough annual in a few weeks.

The topic at hand is trying to inspect the lifters for corrosion. A friend bought a 182 that had similarly sat for a period of time. He flew it for about a year before metal started showing up in the oil analysis. Taking the advice of a well meaning friend, he went ahead and had a major overhaul done. An A&P told him later that he likely only had corrosion on his lifters. Had he inspected the lifters upon purchase and replaced them, he could have gotten more time out of the engine without overhaul. This friend is insisting I get the lifters inspected before I put much time on it. The only mechanic I've talked to said the 0470 lifters can be inspected without pulling cylinders but the 0300 lifters are integral with the engine case.

Can anybody shed some light on this for me? I'm told the cam is down in the oil on the 0300 and should be fine, but the lifters are not and are exposed to potential corrosion after sitting for 15 years. Is there any "relatively easy" way to examine the lifters on the 0300?

[Bruce Fenstermacher]

The hydraulic unit body or follower as it is sometimes called is the outside of the hydraulic lifter assembly. They are what rides on the cam lobe and they and the cam are subject to rust. The lifter hydraulic unit is inside of the follower, likely still holding oil and protected from corrosion.

On a C-145/0-300 you can remove the hydraulic unit without splitting the engine case halves however as your engine is likely to have original style cylinders with staked in pushrod tubes, you cylinders would have to be removed to get the pushrod tubes out of the way of the hydraulic unit covers. The hydraulic units themselves may or may not be held into the followers with a C-clip depending on the year of manufacture of the follower and both types of followers are interchangeable so you might have one or more with or without clips. This is important to know which I will explain later.

The follower and the cam is what you would really like to examine. That can't be done completely without removing at least 3 cylinders. Any combination of #1 or #2, #3 or 4 and #5 or #6. When I've done this inspection, this was the case because, at the time small, flexible affordable bore scopes suitable for such an inspection hadn't come on the market yet. And so I did not look for a way to weave a bore scope to view each cam lobe and follower. I highly doubt it is possible however and would count on removing at least 3 cylinders. Any corrosion, pitting or galling found will require splitting the case to remove the cam and follower(s) for further inspection. Depending on the depth of the damage, followers and cams can be reground to a point. Of course you will be overhauling this engine at this point.

As for the C-clip in the Hydraulic assemblies. If any of your assemblies don't have c-clips, the push rod socket that rides on top of the hydraulic unit can easily be pulled out of place and turned by the suction of oil between the socket and the pushrod as the push rod is removed after removing the rocker arm. IF THIS HAPPENS AND YOU TURN YOUR CRANK, the cup will split the follower and you will be splitting the case to replace it. Until you know you have C-clips installed in all your hydraulic units, best practice is to leave the pushrod in the tube until you can blow a quick blast of air down the push rod to blow it off the cup leaving the cup in place. IF AT ANY TIME you are fooling with the push rod, extreme care should be taken moving the crank and stopping immediately on any resistance and backing off the crank. If you know what it looks like looking down a push rod tube with a bright light, you may be able to see if the cup is jammed. FYI no small Continental engines had C-clips in the hydraulic assemblies unless modified so keep this in mind if you ever are wrenching on any Continental up to the C-145/ 0-300

[c170b53]

I think I’ve posted this pic before, maybe not

Excellent info Bruce and this is what you hope is not the condition of your lifter’s face. Notice most of the wear is in the center of the lobe which makes it difficult to see even after pulling a cylinder. Requires cleaning the face when viewing inside the block which adds to the difficulty. Its my belief that the most likely cylinder to be affected would be number 6 because of the deck angle of the engine in a 170. The reality in my view is worry about after it starts making metal as either you have the beginnings of damage or you do not. Only downside is if there is significant metal produced, metal will get trapped in the journals and the crank gets scored but likely that would take time.

[darhymes]

I cannot comment on lifter condition inspection since my oil analysis and filter inspections have not alarmed me enough to do so.

I did replace all the pushrod tubes with Real Gaskets kits during the last annual. The modification allows some access to the lifters and cam after the original pushrod tubes and lifter cover are removed (without removing the cylinder). Bruce's instructions to blast some air through the pushrod worked just as advertised. Probably saved me from a huge headache...

[Bruce Fenstermacher]

... The modification allows some access to the lifters and cam after the original pushrod tubes and lifter cover are removed (without removing the cylinder). ..

The Real Gasket push rod tube mod or later cylinders with essentially the same mod incorporated will give you easier access to the hydraulic unit. But you still can't pull the follower and inspect the face or see any of the cam.

As Jim notes, with 3 cylinders pulled one needs to inspect each follower face and cam lobe carefully. This requires a good light and small mirror and someone to slowly turn the crank and thus the cam to different positions though I'll bet most defects will be able to be seen someplace without much rotation of the crank.

[rmorton]

I appreciate the detailed instructions and cautions Bruce. This sounds a little beyond my shade tree mechanic experience. I’m tending to agree with Jim that maybe I not go to that much trouble until metal starts showing up in the oil analysis. The motor only has about 600 hrs since MO, but it’s the 15 yrs sitting that concerns me. It would be nice to know if there’s corrosion or not before I spend more money on other things. It has fresh oil now, how soon should I change it again and get an oil analysis?

[Bruce Fenstermacher]

For the most part oil analysis is best when there is several samples to see a trend. Your first unless a metal content is so out of wack, will only be a gauge to compare the next to and so on until a trend is shown.

When I removed cylinders looking for the source of metal we found in the screen, we were looking for piston pin cap wear. We also found two bad followers, one worse than the other and wear to the cam lobes they rode on. We estimated if it hadn't had a bad piston pin cap, that engine may have run another 100 hrs, maybe more who knows. We never really saw any metal in the oil from the followers and cam. just the aluminum from the cap. We of course were only doing eye ball oil analysis.

[n2582d]

Ryan,
You wrote,

… I'm told the cam is down in the oil on the 0300 and should be fine, but the lifters are not and are exposed to potential corrosion after sitting for 15 years. … .

Curiosity got the best of me so I measured how much just the sump of an O-300 holds. Sitting level six quarts comes to about a quarter inch below the top flange.

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Six quarts of water

Of course, in the plane the case does not sit level and additional oil would fill the bottom of the accessory case. The centerline of the camshaft is about 1.5” above where the crankcase joins the sump. The tappets are on the same horizontal plane as the camshaft. Even with eight quarts of oil much, if not all, of the camshaft and lifters do not sit bathed in oil.

If you don’t already have access to one, it might be worth investing in a borescope. I bought a Vividia VA-400 here. It’s impossible to see the tappets with a borescope looking through the oil filler neck or by removing the fuel pump plate on the front right side of the case. That would be too easy! But, as you can see in the following photos, you should be able see most of the tappet faces by inserting the the probe through the two oil plugs. Removing the rockers would give a better picture by allowing the tappet face to be moved away from the cam lobe. The #3 exhaust and #4 intake tappets will be hard to get a good look at.

Click to Enlarge

Click to Enlarge

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Finally, study Continental’s SID 05-1B “Inspection Guidelines for CM Camshafts and Hydraulic Lifters” found here.

[Bruce Fenstermacher]

as you can see in the following photos, you should be able see most of the tappet faces by inserting the the probe through the two oil plugs

Never thought about going through the oil pan. Might be interesting to see what exactly you can see that way. Also wonder how much baffle around the sump will actually hinder this effort as well at exhaust and motor mount. None of these are a snap to remove.

It is said that Continentals do better than Lycoming because the cam is under the crank and the last thing for oil to drip off of a it sit. The Lycoming cam being on top it the first thing to drip dry in contrast. Never thought any of it would be in the oil at anytime as the rotation would really foam up the oil not to mention the drag imposed on the operation of the engine.

[DWood]

Deleted

[n2582d]

Bruce,
I agree, access to the the forward oil drain plug would involve removing at least the center baffling and carb airbox. Don’t think it would be necessary to remove intake or exhaust. In any case, I’d start by seeing what I could through the rear oil drain. As Jim alluded to, the cleanliness — or lack thereof — of the tappet surface might be an issue in checking for corrosion. If it is an issue, one idea might be to zip tie a long straw to the borescope to squirt the tappet with brake cleaner. Or make friends with your proctologist — they’re great with a borescope and really know how to clean what they’re examining!

[jklaerner]

I have also looked at mine with a Borescope after changing oil, through the pickup screen port at the bottom of the accessory case. It’s not perfect, but does get you a good look without pulling baffling around the oil drains

[jklaerner]

An IA I know recommends Aeroshell Plus even for Continentals as it has the additives to protect the cam and lifters.

I was told never to do this if you still have the old pull type starter as it negatively affects the clutch mechanism.

[gfeher]

I was told never to do this if you still have the old pull type starter as it negatively affects the clutch mechanism

My 170B has the original pull starter and I've been running it with Aeroshell 15W-50, which has the same additives as Aeroshell Plus, since I bought it almost 10 years ago, without any starter clutch issues.

[rmorton]

Apparently, I misunderstood or was told incorrectly about the cam being in the oil. I appreciate all the good photos and explanation. I do have a endoscope that can serve as a borescope, so I will try poking around when we drain the oil. According to that Service Information Directive, the inspection is unnecessary until material shows up in the screen, or an audible tapping is heard. However, it also points out that frequent engine running is the key to preventing corrosion on the cam lobes and lifters (no surprise) and if the engine is not run frequently, change oil 4x/year. I'm positive that hasn't happened in the last 15 years.