Owner assisted overhaul O-300

[moparrob66]

Considering the incredible wait time and expense involved in having an engine overhauled by an engine shop, I'm looking for alternatives. I know a local A&P could do a field overhaul, which could be faster and less expensive. Why couldnt I do all the dirty work and track down the best price on each part and put it together under the supervision of an A&P?

 

[Doc Holliday]

Considering the incredible wait time and expense involved in having an engine overhauled by an engine shop, I'm looking for alternatives. I know a local A&P could do a field overhaul, which could be faster and less expensive. Why couldnt I do all the dirty work and track down the best price on each part and put it together under the supervision of an A&P?

I don't see why not. Go for it.

 

[TCABM]

[mention]Jim K [/mention] to the white courtesy phone.

 

[Bell206]

Why couldnt I do all the dirty work and track down the best price on each part and put it together under the supervision of an A&P?

Sure. But best to pick the A&P first before you do any work on your side. Not all mechanics perform overhauls or assisted work. So that may be your biggest hurdle vs the actual overhaul. Good luck!

 

[Racerx]

Would have to find an A&p willing to do it. Some might be reluctant to sign their name off on it or not want to deal with overseeing such a project. That's where having a rapport with your a&p comes in. I suspect when @Jim K did this his mechanic knew he was more than competent already.

 

[Daleandee]

A friend recently did this with the IO360 in his Commander. Learned a lot, saved a little, and from what I understand, had a blast!

 

[Jim K]

Very few A&P's are willing to do major engine work. If you have a good relationship with someone, talk to them and see what they think. I had been working with my IA for 4 or 5 years, and had been doing progressively bigger jobs under his supervision. It also helped that he worked in an engine shop ~20 years ago, so while it had been a while since he'd been in an engine, it wasn't completely foreign to him (it is for a lot of A&Ps).

I will tell you that you won't save much time. I was being told six months, and I did mine in five. Four of that was waiting on the cases and machine work. Knowing what I know now, I think that could potentially be sped up if you're willing to pay a fee to "expedite". I did save a lot of money. I was quoted 50-60K for my io-540 iirc. I wound up around 25. 6 of that was a new cam kit, but I was able to overhaul my cylinders and didn't need any other parts beyond what is required for an overhaul. The real numbers are in the end of my thread: https://www.pilotsofamerica.com/community/threads/ffs-i-need-a-new-hobby.149050/post-3615897

You'll need access to Veryon, which is the company that Lycoming (and everyone else) has farmed out their publications to. Everything is online. I got an old 1980's physical copy of the Lycoming Direct Drive Overhaul Manual and printed and inserted all the updates since that printing, which was maybe 20 pages. My IA allowed me to piggyback on his subscription, so I can't tell you what it'd cost to get your own. I think pretty much any A&P is going to have access as it's the only way to get all the documents you need to do the job. You'll need to go through all the service letters and instructions for your engine in addition to the AD's, and a lot of that stuff is only available on the service.

SB-240W tells what's required to call it a major overhaul. Paul Dye wrote an excellent series for Kitplanes that can still be found online detailing the process. It's not hard if you're comfortable with a torque wrench and carefully following procedures. There's surprisingly few special tools. There is a LOT of time spent researching.

 

[Magman]

IMHO -If you hav prior auto experience, the FIRST thing to do is forget it.

You must go by techniques and tolerances per TCM.

Saying Chevy or Ford is better will not make you popular.

I’ve done some projects this way that went very well with my statement

in mind.

 

[Papa Pilot]

Considering the incredible wait time and expense involved in having an engine overhauled by an engine shop, I'm looking for alternatives. I know a local A&P could do a field overhaul, which could be faster and less expensive. Why couldnt I do all the dirty work and track down the best price on each part and put it together under the supervision of an A&P?

Exactly what I did. It helped that I had the confidence of my A&P by demonstrating my mechanic skills with various lesser tasks.

I disassembled the engine and did all the legwork sending out the internals for inspection. Paid for all the shipping back and forth. I also did the legwork associated with overhauling the engine appliances. Last piece was to chase down parts to comply with a few engine ADs (e.g., lower engine mounts).

Meanwhile my A&P overhauled the cylinders and ordered the necessary parts for reassembly. When I got everything back from inspection/overhaul, I essentially gave my A&P boxes of freshly inspected parts and a bunch of paperwork. In return, I got an overhauled engine. Start to finish was about 4 months.

I basically did all the "administrative" tasks instead of having my A&P do it. Another way to think about it is doing the general contracting when building a house. Saves you a boatload of money.

 

[moparrob66]

I've done 3 auto V-8 overhauls and I did everything by the book. Learned a lot and saved a lot. Any recommendations on a A&P in the Boise area who might be open to this? I'll probably buy a ran-when-pulled core to overhaul as my engine runs great but is way past TBO. I'd rather have the plane down just long enough to R&R as I dont want it sitting engineless for months.

 

[Larry Korona]

Working with a local shop, I overhauled my O320-E2D. I disassembled everything, took the case, cam etc to local overhaul shops, living in Tulsa OK, made the process much easier as everything was done locally. Purchased new cylinders and all hardware. Then it was just a matter of putting everything back together with the assistance from the shop. Learned a lot, and managing the process, made me confident in the final product. Would definitely recommend it provided you have the time and patience.

 

[Half Fast]

Considering the incredible wait time and expense involved in having an engine overhauled by an engine shop, I'm looking for alternatives. I know a local A&P could do a field overhaul, which could be faster and less expensive. Why couldnt I do all the dirty work and track down the best price on each part and put it together under the supervision of an A&P?

I did exactly that with my O-360 last year. No reason at all you can't do it, assuming you have an A&P who is willing and has the requisite experience.

@Salty also OH'd his own IO-360 a few years ago and might want to chime in.

In my case, we began the process in late Nov 2024, and I took the first test flight in late June 2025. I did make the deliberate decision not to do any shipping over the holidays, so that probably cost a few weeks, and I had to deal with some spells when my mechanic was unavailable. Plus, by the time we were finished the plane needed a fresh annual and I had to wait a week or two for my A&P to get to it. Still, I don't think an engine shop would have been faster, and may well have been slower.

As far as expense, the OH, including engine removal and reinstallation, cost ~$27k. The only parts that weren't replaced with new ones were the cases, the connecting rods, and the rocker arms. Everything else is brand spanking new. I worked with Aircraft Specialties and DivCo for most of the stuff, but also got some items from Colorado Air Parts, J&J Airparts, and Wilco Aircraft Parts. My new cylinders are Superiors that I bought from Spruce.

There is a LOT of time and effort involved in researching parts, determining what's been superceded by what, what approved alternate parts are, finding who has what in stock, getting pricing, tracking and inventorying part deliveries, etc. (And of course, the folks who have the best price for an item never seem to have any inventory.) Doing this yourself will take quite a load off your A&P.

If you have a good hangar to work in and have a decent set of tools that you know how to use, there's no reason you can't do most of the job yourself. It's a great learning opportunity, and you'll know exactly what sort of engine you have when all is done.

Plus, there are few thrills greater than leaving the runway for the first time behind a fresh engine you OH'd yourself and that's only had a few minutes of ground running....

 

[Jim K]

Plus, there are few thrills greater than leaving the runway for the first time behind a fresh engine you OH'd yourself and that's only had a few minutes of ground running....

Thrill..that's a word for it...

 

[Half Fast]

Thrill..that's a word for it...

Logically I understand that I couldn't really hold the plane in the sky using my sphincter muscle, but I sure tried.

 

[moparrob66]

So in my search for a core to OH, how important are logs? Does my fresh OH start with a new logbook if the originals are missing? Does its history matter if its gone through according to the Continental manual(s)?

 

[moparrob66]

Another reason for doing the core is that I dont have a hangar. I'd rather not have it engineless and tied down. Any reason the R&R couldnt be done in a weekend?

 

[Half Fast]

So in my search for a core to OH, how important are logs? Does my fresh OH start with a new logbook if the originals are missing? Does its history matter if its gone through according to the Continental manual(s)?

Only the engine manufacturer, or their designated agent, can zero-time an engine. You will have an engine that is zero hours since major overhaul (SMOH), but the total hours will continue. It's important to know the hours on the core, but the details of prior log entries become moot once you do the OH.

 

[Half Fast]

Any reason the R&R couldnt be done in a weekend?

It's possible. Almost inevitably, though, you'll find you're missing some little dumb fastner or washer or hose fitting or something, you'll have to order one, and you'll wait a week for it to show up.

 

[Jim K]

So in my search for a core to OH, how important are logs? Does my fresh OH start with a new logbook if the originals are missing? Does its history matter if its gone through according to the Continental manual(s)?

Technically, it's the same engine even if the only thing you reuse is the data tag, so you write up the Major Overhaul as a log entry. If there are no logs, I suppose you start a new logbook, total time "unknown". I think most everyone understands that a MOH involves measuring and inspecting everything, so anything before is more or less moot.

The problem with buying a core with no logs is that you have zero clues as to the condition of the internals. The crank is really the thing that matters. Everything else is economically replaceable. I think a new crank for my engine is about $15K. Even with logs, there might not be any mention of grinding the crank, but hopefully the bearing part numbers (and/or receipts..) show up. When I did my overhaul I included the measurement sheet with measurements for every part.

Of course, even at that you still don't know if the crank has gotten scarred since the last OH. I was fortunate to find a disassembled engine with all the major parts yellow tagged when I bought the core for the RV-14. If you can mic the crank you at least know what you're getting, but most of the cores I see are unopened, making it a roll of the dice. Do whatever you can to load them in your favor.

Another reason for doing the core is that I dont have a hangar. I'd rather not have it engineless and tied down. Any reason the R&R couldnt be done in a weekend?

It's possible. Almost inevitably, though, you'll find you're missing some little dumb fastner or washer or hose fitting or something, you'll have to order one, and you'll wait a week for it to show up.

Thanks for saving me the typing @Half Fast

 

[Half Fast]

The crank is really the thing that matters. Everything else is economically replaceable. I think a new crank for my engine is about $15K.

Spot on.

I had to replace my crank, and it was by far the single most expensive item. For my O360 it was a little under $8k.

 

[Bell206]

So in my search for a core to OH, how important are logs?

In your scenario, they can be important. For one you will still need a total time in service for that engine. So whether its listed in the logbooks or you calculate it based on those records it still needs to be determined. An engine with unknown TT or other history may also keep a mechanic from assisting with this.

Does my fresh OH start with a new logbook if the originals are missing?

You can, but it does not zero time the engine.

Does its history matter if its gone through according to the Continental manual(s)?

Yes and no. In your case it will depend on the mechanic who signs off the overhaul.

 

[AV8R_87]

In my case, we began the process in late Nov 2025, and I took the first test flight in late June 2026.

Can I borrow your time machine, please?

 

[Half Fast]

Can I borrow your time machine, please?

Thanks! I’ll fix it.

 

[pfarber]

If you are going to IRAN (or overhaul to serviceable limits) then you need the serviceable specs for all parts and the tooling and skill to measure to the .0001 of an inch. Also gonna need some NDT gear to check for cracks. Things get a little simpler if you already decided to replace all wear parts with new... its spendy, but simpler.

The real issue is if you find a part out of spec (say a crank journal) now you are back to the waiting for a shop again. There is nothing special about grinding a journal,,,, but finding a place that won't slam the door when you say 'airplane' again, is the hard part.

I'd budget at least $1k for QUALITY mics/gauges and you will need a temp controlled room for accurate measurements. I have yet to meet an AnP that's ever supervised a build and then signed off on it. People say they are out there. I bet you would need a years long relationship of MX interaction before you gained their trust, and even then many simply wont.

 

[decalogue]

I’d get the STC to put a 180hp 360 in it, find a gently used 360 and prop on barnstormers or the like and go that way.

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Spending money on a 300 doesn’t seem a good use of time or money

 

[Bell206]

I have yet to meet an AnP that's ever supervised a build and then signed off on it. People say they are out there.

There are several examples of assisted OHs on PoA to include other heavy mx projects like an entire recover that was assisted by mechanics. But while there are mechanics who provide those assisted services, there's definitely been a reduction in those types of mechanics for number of reasons. So why not fill that void and offer assisted engine OHs since you seem to understand the basics of it?

 

[Magman]

Currently I almost exclusively work with long time clients doing

Owner Assist projects. There are some Ground Rules that must be followed

If these relationships are to continue.

1. Creativity is at a minimum. There are set procedures that cannot be

altered. Attempting short cuts rather than approved service techniques

is counter productive.


2. Since I will be signing I must oversee to the extent necessary. A rebuild

project may entail several trips to monitor progress and plan ensuing

steps. Other times I might insult YOU by insisting that I am present

for things like torquing a cylinder installation.


If you are “ thin- skinned” and can’t deal with having to re-do safety wire,

change wire routing and other tasks than Owner Assist is not for you.

 

[moparrob66]

I have a couple A&Ps I need to meet and who knows, maybe I'll keep the plane?

 

[Half Fast]

In my case, and that's only one example, actually assembling and installing (the part that requires A&P supervision) was less than half the job, maybe 1/3 of the total effort. Another 1/3 was taken up by removal and disassembly, and another 1/3 (maybe more) was spent researching ADs, part numbers, alternates, suppliers, etc., and managing procurement and outsourced shop work.

 

[flight_addict]

Exactly what I did. It helped that I had the confidence of my A&P by demonstrating my mechanic skills with various lesser tasks.

I disassembled the engine and did all the legwork sending out the internals for inspection. Paid for all the shipping back and forth. I also did the legwork associated with overhauling the engine appliances. Last piece was to chase down parts to comply with a few engine ADs (e.g., lower engine mounts).

Meanwhile my A&P overhauled the cylinders and ordered the necessary parts for reassembly. When I got everything back from inspection/overhaul, I essentially gave my A&P boxes of freshly inspected parts and a bunch of paperwork. In return, I got an overhauled engine. Start to finish was about 4 months.

I basically did all the "administrative" tasks instead of having my A&P do it. Another way to think about it is doing the general contracting when building a house. Saves you a boatload of money.

I recently did the motor mount bushings on my o-300a and I probably shouldnt have loosened the mounting brackets to do this, but I did and now it seems the thru-bolt is leaking at the mount bracket while the engine is running. Any suggestions or experience with this?

 

[Dan Thomas]

The real issue is if you find a part out of spec (say a crank journal) now you are back to the waiting for a shop again. There is nothing special about grinding a journal,,,, but finding a place that won't slam the door when you say 'airplane' again, is the hard part.

For a car, maybe there's nothing special. For an aircraft crank, it needs re-nitriding after grinding, and those shops are scarce. Only the littlest Continentals (like the A-65) did not have nitrided cranks.