To buy or not to buy

[edbooth]

A question for those of you that have been inside of your continental 0 300. I am not familiar with the continentals. Can you remove the pushrods and pull the lifters through the lifter bore? My goal is to inspect the cam lobes through the lifter bore. There appears to be a service directive regarding this but I can't tell if it applies to the 0 300.

You cannot see the cam thru the lifter bores, the cam follower that the lifter sets in gets in the way. The only way to move those is to split the case. ....

[GAHorn]

I like the idea of pulling a jug or two but understand this involves somewhat major surgery. Pulling the baffles is a pretty good job itself Would an annual would take us pass the interior of the cylinders? Even with a scope? Would really like seeing the crank and inspecting some came lobes would, i hope, give me enough info for a pass/fail. And if fail, I buy the airframe for $8000 and put an 0-470 in it. Case solved! Oh, they would still have to agree to that wouldn't they...

I HATE the idea of your "pulling a jug or two"...or doing any other disassembly of this engine....unless you like the idea of introducing the chances of creating new oil leaks and possibly exposing it to the possibility of spun bearings, cracked/broken fasteners/thru-bolts, etc etc.
If the airplane is as clean as you've already discovered, the engine is likely just as fine. Simply sitting is not in itself a huge risk, if it's been indoors and in a reasonably dry climate like N. TX.
If you like this airplane, ...Annual the airplane and buy it before someone else, less cautious, snaps it up. The Annual Inspection should reveal any serious discrepancies, and anything discovered after you own it is the risk of ordinary airplane ownership.
(And if I were the seller, I wouldn't allow you to open up my engine or fly it "an hour" until you've made a deposit and a letter of intent assuming the risk of the flight. It's unreasonable to expect a seller to assume the risks of your determination to own a "good as new" 60 year old airplane. Any warranties expired a few decades ago.)

[Extrakatana]

Thanks to everyone for their responses. The best way to learn is through experience and I appreciate tapping into yours.

TCM's SID 05-1 obviously doesn't apply to the O-300 since it definitely shows the followers coming all the way out.
http://www.tcmlink.com/pdf2/SID05-1.pdf

Has anyone scoped through the filler neck? Can you see any of the gear train on this engine? Anywhere else that might be able to be scoped that would ease my stay up at night mind that there might be corrosion inside this dormant engine?

[GAHorn]

Does the engine RUN?
Is it SMOOTH?
Does it make static RPM?
Does it have good compression according to a differential compression test?
Is the oil filter clean?

Guess what? It's a good engine!

Yes, if you look into it's bowels there will be gunk and junk and dark stuff. Healthy engines are not surgery rooms. They make dirt. They are never sparkly clean. That is NORMAL.

Did you ever hear about the guy who was so worried about his girlfriends virginity that he lost her to another?

[canav8]

Is the aircraft in an environmentally controlled hangar or outside? Ask the owner if he has hand propped the engine every once in a while or did he run it. If the engine didnt get up to operating oil pressure and the engine was just hand propped, the owner wiped all the oil off the cam lobes and corrosion has set in on the lobes. That and rings could be the next to go. Your cam will go flat in a short period of hours if there is corrosion on the lobes. You might be able to get the compression up by running it but it is more probable that the oil was wiped off the cam lobes and corrosion has set in. Good Luck, D

[GAHorn]

Unfounded horror story. Read whats already been said about this engine.

[canav8]

Unfounded horror story. Read whats already been said about this engine.

Thanks George. Disregard previous post. Go fly the plane!

[c170b53]

George's suggestion of checking static rpm will probably tell you more about the overall health of the engine than horrorscopes. That's not to say everything is perfect as he suggests but it's a basic starting point.
Just because a cam is worn doesn't mean the engine wouldn't be smooth. A cam lobe and follower could wear through their hardened surfaces and continue to wear. If the screens were cleaned, a small flake or two might not make a new owner aware the wear is present until a static RPM check was carried out
In my opinion the screen will tell you when your experiencing a major failure in the engine.

[BEEZERBOY]

run it, compression check it, check the screens, get a spectrographic oil analysis. scope the bores looking for scrape marks indicating stuck/broken rings, if you see skid marks in the bore.... pull that one. I would not pull cylinders just for fun... you should be able to pretty much tell the health of the engine by these standard methods. do an annual on the airframe. when you run the static RPM check be sure the right prop is on there... that sets static. also check the accuracy of the tach, since they are known to lie. try to pick a standard day to do the run, or make compensation

[GAHorn]

One more trivial thought on all that.... one random spectroanalysis oil sample will not tell you anything much...save your money.

Unless you are going to use oil analysis on a regular and regimented basis, using the same laboratory (and not all labs are the same or use the same methods)..... don't bother with a one-time sample in the false belief it will tell you a dang thing more than cutting open the filter will.

Such gymnastics of oil analysis and engine disassembly will only delay and confuse the consummation of the purchase, and provide virtually nothing in assurances beyond what the 100-hr inspection will reveal. IMO

[n2582d]

Has anyone scoped through the filler neck? Can you see any of the gear train on this engine? Anywhere else that might be able to be scoped that would ease my stay up at night mind that there might be corrosion inside this dormant engine?

I've never done it but it seems to me the logical place to "horrorscope" the O-300 would be through the oil drain holes. Should be able to see the cam lobes quite easily. Checking for sump corrosion would be a priority if I were in there with a scope. The challenge would be cleaning the residual oil well enough from the bottom of the sump to see anything.

[Extrakatana]

Thank You for addressing that question Gary...and insightful. My main concern other than the cylinders, which is common knowledge that can be scoped, is the cam lobes. TCM has a directive on how to visually inspect the lobes (obviously important) but apparently doesnt apply to the O-300. The condition of the cylinders and cam will give better understanding.

Can anyone confirm if the cam can be inspected through the oil drain?

I have heard the word screens plural. This engine has a spin on oil filter. Would it still have a screen? Or screens? I know lycoming has a screen and filter in my 360. Don't know Continentals.

Agree one oil analysis wont do much. All good responses thanks!

[cessna170bdriver]

Thank You for addressing that question Gary...and insightful. My main concern other than the cylinders, which is common knowledge that can be scoped, is the cam lobes. TCM has a directive on how to visually inspect the lobes (obviously important) but apparently doesnt apply to the O-300. The condition of the cylinders and cam will give better understanding.

Can anyone confirm if the cam can be inspected through the oil drain?

I have heard the word screens plural. This engine has a spin on oil filter. Would it still have a screen? Or screens? I know lycoming has a screen and filter in my 360. Don't know Continentals.

Agree one oil analysis wont do much. All good responses thanks!

I've never tried it, but I'd say the oil drain holes are the best bet for access for scoping the cam. If you're an association member, go to the members only page and download the 2nd Quarter 2006 170 News. On page 15 you'll find a photo of the bottom of my engine during assembly, before the oil sump was installed. There in all its glory is the camshaft. You'll have to look in both drain holes, as the carburetor intake plumbing in the sump will block access between the front and rear. I don't think looking down the oil filler is going to get you much at all. IIRC, it turns into a channel inside the accessory case about the size of your thumb that leads to the back of the sump.

If you want to look at the gear train, the best bet is to pull a mag and look directly (check page 8 of the 3rd Quarter 2006 170 News). I'm with George though, that the best diagnosic is to check the screens and/or filter. If there is physical damage to moving parts you'll most likely find the results there.

[Extrakatana]

Did a more thorough inspection today under the knowledge a complete annual would follow if all looked good today.
Scoped all of the cylinders.....looked good and saw hone marks. Was able to look at 2 lobes on the cam through the dipstick tube.....all looked good. Did a static test and changed the oil/checked the filter. Progressing and will post some pics once this works out.
Thanks for the help.

[T. Gandy]

I must be a lucky stiff. I bought two airplanes by looking them over and talking to the owner - a 1946 Champ and a 1947 Stinson Voyager. I might have had a mechanic do a prepurchase on the Stinson, but it was 1500 miles away. It doesn't hurt to be thourough, but if an airplane is going to burn you, you may never see it coming no matter how close you look. As engines go, the only 100% guarantee of what you have is a tear down - not going to happen.

IMHO, if you like the airplane and the owner and if the owner has a good reputation (didn't someone say they knew this owner?), pull the trigger and buy it. Like a car, you can tell a lot about how an airplane has been treated by how the exterior/interior look. Scratches, dents, torn/worn fabric, bad tires or under inflated tires always point to a possibly tired plane on the inside, too. In a lot of ways, the outside reflects what's on the inside.