0-300d powered 170 getting a prebuy and annual. I’ve made the classic mistake of getting a little attached to the idea of buying it.

It had sat for several years without flying, so I had the shop borescope the engine as the first step. The found rust on the cylinder walls and are suggesting removing all 6 to get them honed, I assume they’d check the valves etc and repair whatever needs to be dealt with.

I’d really like to buy this thing, would this be a deal breaker for most people? I have the budget to do it, and beat up the seller on price so even with this work I’m probably OK on the total price, just not getting a great deal...

How many years did it sit and how much rust?
The O300 sits Better than others (cam under crank) but you can still get rust on the cam lobes after years of sitting.

For the labor cost to clean up the old cylinders, I’d seriously consider just buying new.

From what I can gather, it sat for almost 4 years, in a relatively dry environment. I was hoping it escaped corrosion, but it didn’t. I don’t know how much rust, enough that the a&p thinks they should come off.

It’s at almost 1200 smoh, buying 6 new nickies would almost push me into just doing a field Major at that point right?

Maybe I should forget the budget and put the stoots io-390 on there.

The cost of six new cylinders is no where near the cost of an overhaul.

The bottom end on an O300 is pretty solid and rarely has problems. But the crank, sump and accessory cases are getting harder and harder to find. Would suck to tear it down and have to find a sump.
Plus O/H means mags, starter, generator...it adds up to do it right.

I’d be tempted to hone the cylinders, throw new rings in it and see how many more hours I could out of it. If you have the cash, try to pick up another O300 to overhaul at your leisure for when this one gives out but keep flying in the meantime.

Really depends on how the rest of the airframe looks and what you’re getting it for.

I got mine for pretty close to free but will have a lot more than that in it before she’s flying
Buying an old airplane is the cheapest part of owning an old airplane.

David has lots of good advice above [emoji1360]

My take: Let's assume you settle on a price and buy it.

Don't bother with a top overhaul as your initial step. Give it an Italian tune up then look at the cylinders again.

2650 cruise at 5' MSL leaned to the max. Make sure you have gliding distance to land on field.

https://en.wikipedia.org/wiki/Italian_tuneup

Aryana wrote:David has lots of good advice above [emoji1360]

My take: Let's assume you settle on a price and buy it.

Don't bother with a top overhaul as your initial step. Give it an Italian tune up then look at the cylinders again.

2650 cruise at 5' MSL leaned to the max. Make sure you have gliding distance to land on field.

https://en.wikipedia.org/wiki/Italian_tuneup

That’s what I would do too. If your going to either top it or hone/re-rering then attempting an Italian tuneup doesn’t cost you anything and might actually result in getting some additional time out of the engine as is.

All good advise above. These are good engines. You may want to check total time and what was done at the last overhaul. Is the crankshaft standard, better chance of it being used again, new cam and lifter bodies, information if you have to go deep. New cylinders and pistons? The pistons can be a weak link if they were not new as the ring lands can be worn out of limits, and could be the case if they were new, this if you are going to hone. Discuss this with your A&P but remember at some point between TBO this happens and it is ok your are not at TBO yet. Some A&Ps will not reinstall parts if they are out of limits, you need to know to make your decision.

Rust is a hard call to make as what to do, if you are going to run it, change the oil after maybe 5 hrs. The rust will remove material from the rings, the pits unless really deep will not hurt the cylinders. The engine will tell you whats going on with oil consumption and compression. I wouldn't be to concerned with oil consumption unless very excessive. Oil consumption can go up with rust and then back down in some cases, as the rings reseat.

Hawk & I have had this issue with a couple C-182's and their O470's and a O300 in a recent purchase of a C-170

1 of the O470's had been sitting for 6 yrs. The other had been sitting for 10 yrs. The O300 sat for a couple of years.

We followed Mike Busch procedures about powerplant resurrection and "so far, so good". All three engines are performing well and getting better with each flight.

We kept them all close to the airport for the 1st few hours and ventured out further and further until we were comfortable.

Here is a link to Mike's article about powerplant resurrection:

https://www.savvyaviation.com/wp-conten ... ection.pdf

This procedure is like breaking in a new engine and we got lucky. Of course, we bought the planes at prices that afforded an engine o/h if necessary. You might want to read the article and determine if this might work for you.

Rich

Thanks for the advice. I’ve used the Italian tune up trick on some old cars, but the downside of that going south is less severe...

To add another layer to this problem, I will need to take the thing on a long ferry flight to get it to its new home (yes, I know that buying long distance is dumb, but sometimes you have to say f it...).

I guess that makes me lean in the direction of getting the cylinders honed so that I’ll have more peace of mind on the trip. On the other hand these engines seem most likely to come apart in a dramatic way within 10-20 hours of any major surgery...

I’ll read that mike Busch article. Thanks

Good article.

Never thought of fogging the engine before starting it. Might have to start. I have done that before it gets parked.

I pull the spark plugs, use the starter to pre-oil the engine, then fire it up. If all seems right in the warm up and very thorough runup, I will fly it good and hard. I don't bother doing a boroscope or compression check until after (unless I'm suspect of something). Done several this way. I haven't pulled jugs for corrosion in the cylinders. It's so far been because of bad valves or broken rings.

Also, the cylinders that the exhaust valves were off their seats will fail the compression check (which is why I dont bother til later). The carbon in the seat or valve will swell up slightly by moister or whatever and not allow the valve to seal. Sometimes you might have a "dead" cyl when running up until you get it warm and bring the RPMs up to high enough internal pressure. usually 12-1800 rpm. At least thats been my experience

Logistics question- the airplane does not have a current annual, so I can’t just fly it hard for five hours. On the other hand the a&p would probably not want to sign it off as airworthy in its current state. Would a long, aggressive ground run after fogging it etc get it to the point where it could pass a compression test and get signed off?

You will need a A&P sign off for a Ferry Permit. A hard initial engine run with rust in cylinders can cause cylinder over heating from the added friction the rust causes. This can cause piston scuffing and cylinder damage, I observed this in one case. Depending on the amount of rust the guys who have had the best luck, lubricated and ground run for short periods keeping temps down, bore scoping, until most of the rust was cleaned up, compression check. Fly short period, change oil to remove the rust and material that came from the cylinders and rings. Running hard later would be ok and probably good. In view of the time the plane has set after the rust has mostly cleaned up if you should go this route, oil change would be good before flight. And 5 hrs later.

In 50 years observing the rust issues, depending on the amount of rust present I have seen more engines turn out ok than not. I don't know how much the life was shortened. And a few required a top overhauls later as the oil consumption was excessive, the rust cut groves in the rings. The one mentioned above with the scuffed cylinders required replacement of course.

Pre oiling is desirable and can be done easily by pluming into the the oil pressure out let on the case, remember to remove the elbow as there is a restrictor in there. I have used those little pumps on a electric drill.

What are the cylinder compressions as tested per Continental SB 03-3 (engine warm)?

Aryana wrote:What are the cylinder compressions as tested per Continental SB 03-3 (engine warm)?

No idea, it hasn’t run in 3-4 years. Prior to sitting, compression was great in all 6.

I can’t see getting a ferry permit, it’s not local to me, and I doubt there’s anybody interested in flying a questionable engine around for a while...

Sounds like the consensus is to fog it, pre-oil it, ground run a few times without letting temps get too high, and see if we can get decent compression numbers. If so finish the annual and fly it like a new engine for break in, change the oil at 5 hours or and hope for the best...

Dirt911 wrote:

Aryana wrote:What are the cylinder compressions as tested per Continental SB 03-3 (engine warm)?

No idea, it hasn’t run in 3-4 years. Prior to sitting, compression was great in all 6.

I can’t see getting a ferry permit, it’s not local to me, and I doubt there’s anybody interested in flying a questionable engine around for a while...

Sounds like the consensus is to fog it, pre-oil it, ground run a few times without letting temps get too high, and see if we can get decent compression numbers. If so finish the annual and fly it like a new engine for break in, change the oil at 5 hours or and hope for the best...

I would change the oil after the first few runs AND at 5 hours.

Are you sure you want to do this? I understand the connection to wanting to buy something, but you are talking about an airplane across the country with a known issue and perhaps other unknown issues. Both my airplane purchases were relatively long distances, but I walked away from more than one when it wasn't up to snuff. If you can afford the worst case, would you rather overhaul this engine or find a 170 with an O-360 and pay up front. The best deal I didn't buy cost me $1000 in inspection and airfare, and that airplane ended up crashing a couple of months later on a ferry flight.

jcadwell wrote:Are you sure you want to do this? I understand the connection to wanting to buy something, but you are talking about an airplane across the country with a known issue and perhaps other unknown issues. Both my airplane purchases were relatively long distances, but I walked away from more than one when it wasn't up to snuff. If you can afford the worst case, would you rather overhaul this engine or find a 170 with an O-360 and pay up front. The best deal I didn't buy cost me $1000 in inspection and airfare, and that airplane ended up crashing a couple of months later on a ferry flight.

Totally fair point. My initial reaction to the mechanic telling me what he found was to move on. But this 170 has some mods I really want, it has a great history and is nicer than most I’ve seen. Plan is to fly it for a couple years while saving my money and then make a decision to commit financial harakiri and do an engine swap, rebuild the 0-300, or buy a 180.

So yes, I think you’re right that it would be smarter to move on, but buying a 60 something year old airplane is pretty dumb to start with, so f it, might as well hit every branch on my trip down the dumb tree.

What are some of those mods you really want? We can probably talk you out of them...or at least tell you what they're actually worth...

I’ll tell you a mod you don’t want.... that o-300-d.

Don’t get me wrong, I’m cool with the o-300-a/b/c or even a c-145 as they work fine for a two place airplane assuming you put a climb prop on it, but the o-300-d is a different animal. It requires a different prop (which might make the paperwork a pain), has the right angle starter adapter (so no b&c starter), and you get the extra weight of a vacuum pump you don’t want (get a g5 or dynon).

I bet the airplane is north of 1425lbs, and much of it is that engine.

Stuff to think about....

The O-300-D is the same as the rest of the 6 bolt O-300's except for the right angle starter adaptor which allows for a vacuum pump.
You're not required to run a vacuum pump. You can block it off with a plate.
The right angle starer isn't so heavy to add any meaningful weight to the plane.

The prop is the same as all the rest of the 6 bolt O-300's. (EM vs DM or MDM) Nothing special and the 170 association has the STC for sale cheap if the paperwork isn't in order.