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December 6th. 2025 and the engine is back. In the end it was just a set of rings.

I pretty much got it back on the mounts on my own but I did get a bit of help to seat the final rubber. That was a couple of days in the end. Now I should have hooked up the small alternator and a couple of pipes while the engine was a few inches off the mounts. I thought I could struggle with the lack of clearance later… That decision soon came back to bite me.

Yes, heres’ the first gottcha, all that stuff had to come out now.

The plug at the back of the alternator needed another 1/4″ or so to fit in and I couldn’t do it with the engine installed. Yeah, should have done it when it went in. So a bit of work to get there, then 2 seconds for the plug, then it all back in again. Chalk up another day gone.

I’ve bought a larger heat exchanger. This ones a bit longer than the last. Laminova ECD54-329 the previous was the 250mm version. I hope this will improve the cooling balance between the coolant/cylinders and the oil. If not I am going to need a bypass system which would be more pipes and complexity. I had quite some challenges fitting this longer unit.

It really doesn’t fit. I tried denial for a while. That radiator is just too close.

So by mid January I pulled the radiator, had the corner chopped off by my excellent welder friend and now there is good clearance. Of course I had a lot to go through before that happened.

This is after two weeks work fitting electrics and pipes, I realised I needed to pull the engine out again. Just one little -4 size pipe for the oil pressure simply could not be fitted. You couldn’t even see it and braille skills required! I had no idea that was going to be so difficult and I was reluctant to pull the engine again given how tough it is to get the mounts sitting just right.

Now we are at 30 December 2025. I got my little oil pipe on with the engine removed back a few inches. In the end I had two very skilled LAME’s help me get it back on the mounts. This is not a one person job. During the process I was asked, “Get me a bigger hammer” Now coming from fixing guitars as a background I don’t tend to think that way on airplanes. You need to know what you are doing. I will say the engine now sits on its rubber Lord Mounts better than it ever has.

Finally, ready for some leak testing before the first ground run.

I’ve decided to leave off the exhaust wraps for now. I think I need more heat in the cowls after flying to help it cool down at a closer rate to the coolant. Particularly while I am using straight mineral oil.

It has been a huge job to this point.

Before the first start attempt I did run the fuel pumps. I can get full pressure without the engine running which is great. I had a few leaks and addressed them. A couple of things not done up enough.

24 Jan 2026 I ran the engine. It started on the third try. I was pretty happy with that. It meant I hadn’t stuffed up all the electronics and ignition leads for a start. A few things on the first brief run had to be tightened up. I then got a start on the first crank and ran for a few minutes at 1000rpm and then up to 1500rpm. Well that extra pressure showed up a significant coolant leak. Otherwise I seem good.

Well you can see what leaked out overnight.

On investigation and some research it looks like the O rings in my water pumps have failed. I never touched them during the reinstall and they didn’t leak before. The idea fits perfectly with them run wet for a while and then the coolant drained and the system dry for over 6 months. So I pulled the fittings and had to drive home again (1hr 45mts each way) after hoping to be close to flying. We have the weekend then a public holiday so I might get two little O rings mid week. I think there are about four other leak points. I’m not sure if just a tighten will do it but the O-rings are a game stopper.

Replacing those is not negotiable so that’s the next step. Then another run. Of course I need a ‘spotter’ each time to let me know if there are leaks or problems as I can’t see the engine from the cockpit. If the other areas are leaking, I may need to replace fittings. They have to be perfect in the coolant system compared to oil or even fuel. Water is thin! Wish me luck…

As I explained in the post ‘‘engine-rebuild-1‘ the engine became so tight I couldn’t start it. Its been to the engine shop and lived there for five months. This puts my circumnavigation plans back until 2027 now.  First up they ‘pulled the jugs’ or in plain speak, removed the cylinders.

As it turned out the ‘bottom end’ of the engine was perfect, no rust, no problems. Nothing to see here. That was good news as I was expecting a bulk strip with a rusty camshaft and who know what else.

In the cylinders things weren’t too bad either.

A tiny bit of surface pitting but of no concern.

The bores only needed a light hone with the ‘dunny brush’ and the valves were no problem. This shot is after the work with a lot of preservation oil. The cylinders were not glazed either so run-in or break-in worked out OK.

Eeeerrrkkk!!

The rings however….

Huge amounts of rust at the rings, locking them solid.

Even after a clean up these are not so pretty.

There was also corrosion just at these intake ports but not down the tubes. It was confided just to the heads area.

New rings were of course required. These came from the engine builders in the USA.

They don’t seem to be a standard part, they are different to the old rings. The top ones have TOP 5.319 which would be the bore size. I have 390 cylinders, I assume bored out, and oversized pistons given they are marked with xx.

The oil rings have no markings. The following is what was sent to help the install and I’ve put it here so I have a permanent record in an easy to find place.

Here is some specs. *Cylinder base nut torque spec. Lube the threads and the matting surfaces of the spherical nut generously with Carrillo bolt lube I sent you I can take a pic for reference, use the Lycoming torque sequence but using our final torque value of 60 ft pounds on the 1/2″ and 32.5 ft pounds on 3/8″ studs. Make sure you torque wrench is 90° to the engine vertical centerline as its super easy with base wrenches and the higher value to cover torque as they are always in a awkward area its not near aa easy as a regular Lycoming.

*Pistons are directional I will send a diagram so you can confirm nothing gets flip flopped.

*Piston rings must be installed using a ring expander if you try to roll the piston rings on you will very potentially experience ring issue or micro welding as the ring side clearance is tight and the square ring desing will damage the groove, always oil the rings and grooves before install, make sure the ring rotates freely in the groove while compressing the ring slightly. Stagger rings 180° so staring at the piston the ring end gap will be top ring 12:00. 2nd 6:00 and then I do the oil at 11:00 or 1:00 just slightly offset from 12:00. Top Ring end gap. .029″-.044″ 2nd Ring end gap. .029″-.047″ (2nd ring should be .0025″ to .0045″ larger than the top ring gap Oil Ring end gap. Min .020″ These values fall in spec but for your build I would not open them up if they are above the minimum value and I already added .0035″ to the 2nd rings chances are you will not have to touch them but must confirm.

*cylinder honing notes. I don’t know if they need to touch them up but they can’t go too big on the cylinders they will have to check the dimensions. If they do hone they need to target for a rvk 80 and a rpk under 10 are the 2 most important values. Hopefully they have a profilometer maybe confirm with them so they can check surface finish, its very critical. One other thing to note the ring goes right to the top of the sleeve like .020″ from the top so very close there is an additional. 070″ of room before they crash into the head, they should have no issue with this unless their is a tooling clearence problem but its worth noting as its not typically how lycoming does it they normally have tons of room. Piston to cylinder wall clearence is .0065″ to .012″ If they struggle on the hone we could always resleeve your cylinders if needed.

*A thin base shim gasket was shipped that will be installed on the cylinder first then your standard lycoming o-rings. The engine deck surface and cylinder surface must be extremely clean and dry before install, a grey scotch brite pad is ok to clean up little scratches or debris, teeat it like a automotive head gasket instal no nics or high spots, from scratches, ect. Clean and dry. Will send pic for install reference.

*Cylinder install. We need to talk about this before done as very critical and easy to mess up critical components if not done right, I can discuss procedures that will make it easier and less likely to cause any damage but here is overview so you have an idea of what is required. when installing the cylinders on the plane we will talk first. During the procedure its very easy for the cylinder to rick and for the skirts to hit the studs so extreme caution is needed, but need a smooth flat surface that is level to the crank and can set height right (I can send pics and will discuss more as this sets you up most for success, failure, or just pulling your hair out! Lol), remove the lower coolant fittings with the 2 allen bolts so it sits flat on the surface, load the pistons with inner clips already installed and push them in to wear the wrist pins can slide in still in the relief cuts so once the oil ring is in just a hair further, the rotate the engine to where the rear ro is highest up then install wrist pin and clip, rotate so you instal the front wrist pin and clip then push cylinder on and follow lycoming torque sequence for thru bolts not single cylinder. (Can send diagram for sequence if needed) Thanks and keep me posted and I will send you a few diagrams on the torque spec, piston orientation, etc.

These are the instructions verbatim. Nothing further was sent. The engine shop back here in Australia were happy to go ahead and are very confident the engine is correctly back together.

I was very please to get the engine back to the van for transportation. It was a mammoth day with 10 hours driving to get it to my hangar.

I mowed the lawn on my last trip, so this is 5 months growth while the engine was getting a new set of rings. The shop here have great people and do quality work but they can’t find more staff so things take a crazy amount of time to get done. I am both grateful and frustrated at the same time.

Back to business, the reinstall is proving to be an enormous job with a lot of challenges. I’ll update all this in another post.

What happened to the engine? Why did the Rings rust?
Haaa we are finally here. Water causes rust. My coolant level hasn’t moved during the test flying. There are no cracks in each cylinder  and they all had similar amounts of ring rust. This rust is confided to the heads.

The rust got WORSE the more I flew. That’s crazy. It got so bad that the engine became harder and harder to start until is didn’t. The rust was stopping the rings from moving and they were catching in the bore as I tried to crank the starter. No dice.

A borescope confirmed terrible rust after the ‘no start’ that was not present at the beginning of the test flying. I did a check before the program began. We had a little surface rust initially but it diminished with ground runs and a couple of oil changes and filter cleans. I was always concerned about the engine tightness from Day 1, perhaps this is not the worse thing that could have happened.

Condensation! (or Sweating)
Yeap. It must be producing water from the atmosphere that runs down the cylinders and collects on the rings. For ‘break-in’ I use Aeroshell 100 straight mineral oil and that has no ‘detergents’ or rust inhibitors, so we have no corrosion protection either.

I believe when warm, moist air comes into contact with a cold surface, the air right at that surface cools down. Since cooler air can’t hold as much water vapor as warm air, the excess moisture condenses into liquid water droplets on that surface. As best I can tell it depends on the dew point or humidity at the time as to how much or little temperature difference (DeltaT) can cause the problem. Probably around 20-40F gap would be enough to give me this very expensive situation. That’s not much at all.

With my cooling flaps open after landing, given under the cowls would be heat soaked, I now produce a rapidly cooling surface while my coolant at 160-200F stays much warmer. So I get a temperature mismatch. My rapidly cooled external cylinder surfaces drop below the dew point of the surrounding hot engine bay air = sweating. 

This also produced the 5 month gap in my program (as I keep saying) and I’m already another month gone in getting the reinstall started. I might be flying again in February 2026. Then I have to bed the rings in which might be 20-40 hours before I can resume the test program.

I think I might leave the cowl flaps closed after landing now! Maybe lean out the engine then and be in no hurry to shut down. Its a plan. Once the run in is completed I’m thinking Camguard oil additive might be good too when I go to the Aeroshell 15W50 Oil or something similar.

Removing the engine for its bulk strip was, as expected, a big job. Unlike air cooled and a basic magneto and carb engine, this one has a lot more things hanging off it.  July 6th 2025 I made the decision, or rather the engine told me, it needed a proper doctor and serious surgery.

These shots are with things intact.

During removal I took around 200 photos. Just close ups of each item as I removed them.

Along with the photos I have 6 pages of notes. This will give me some kind of order for the reassembly as well as a few things to watch out for.

A lot of work went into making these things fit. Clearance to the cowl is around 1/4″ in places.

One thing I will be doing is replacing that Laminova unit with this longer one. I ‘think’ it will fit but the install will be a challenge. The brackets took me about a week last time to figure out and fabricate.

All over the hangar are boxes like this now full of engine parts.

It was easy to get off the plane once every thing was removed. Of course there were a few hidden things that needed undoing. Going back it I’ll have to have the engine not quite on the mount and add a few pipes and bits before seating it in place.

All out. Kind of sad after so few flying hours. Going back in might be a couple of weeks work instead of the four days to get it out.

I never thought I’d need this engine hoist I bought for the initial install…again.

This is the VW van I have borrowed, a perfect size for this job. It wasn’t available for a few weeks after engine removal but it didn’t matter as the engine guy was away in the USA.

This is in Cobram, Victoria loading it onto ‘the floor’ at the engine shop. It’s about 350km from my hangar. It was seven hours on the road that day. It would take around 1 hour by air if the engine was happily in the plane and I didn’t mind using a bit of fuel. Driving, compared to flying, may not be my favourite thing.

Now I wait….

My new AC-Aero Gladiator LIO-390 engine has had 30 hours of flying. It now needs to be removed and sent to an engine shop. Maybe a bulk strip, which is effectively where the engine is disassembled with the case split open and parts are inspected. Until they look pull the cylinders off we won’t know. At a minimum I will need a new set of rings.

Here’s how things look before I start pulling items off and remove the engine from my plane. It is not going to be a small job.

As it comes apart I will be taking a lot of photos and writing myself notes. Yes, its going to be yet another journey. My plans for round the world next year might have to wait until 2027!

What Happened?
Good question. Lets start with before the first engine start after getting everything installed on the plane.

You can see or rather hear there is a bit of groaning going on here as I slowly pull the prop through by hand. This engine is tight. This is way back on 22nd of September 2024.  I was told at the time by the licensed guys in the hangar that this sometimes happens with newly overhauled engines, it usually resolves in a few hours of flying in their experience.

You are looking at the inside of my cylinders.

Yes, that yellow colour does not mean I have gold plating.

I was still worried about my groaning powerplant so I bought an endoscope for looking inside the cylinders. They are usually called borescopes for engines but this is what was on the box. Anyway the cylinders were full of rust!

What happened?
It turns out that my engine was delivered without preservative oil. Something conforming to MIL-C-6529 Type I is the norm. Now to be fair, I’m sure they did put a small amount of preservative in it, probably from a spray can. This is mentioned in the log book. The engine did have desiccant spark plugs which is the cream on top.  Another factor is that the engine is not meant to be full of oil when shipping to Australia from the USA. Maybe this is why nothing much was inside to prevent rust? It was a good 12 months that I spent putting the thing on my plane before we found this problem.

OK, should I have thought of this? Well you’d think I’d get a heads up from the engine builders if it was sent with just a spray of inhibitor and nothing else. It is standard practice to inhibit any engine that might be sitting around for more than a few weeks. I would no more check that this had been done than I would check the wheel nuts on a new car. I did not check every exposed nut for correct torque either. I put inhibiting in this category. All this time I was in a hangar with professional aircraft mechanics, it never occurred to them either. Why check for something that is always done as a matter of practice. So still my fault? Yes, I’d say so. I should have been totally paranoid about rust and done the job myself.

What next?
On advice, I changed the oil again, checked the filter and ran it for a few hours. Then I got my endoscope out, had another look and changed the oil and filter again. There was less rust the second time although definitely rust particles in the filter. Same again, I ran it for a few hours and did the filter, oil, endoscope. Well, less rust this time and short of pulling the cylinders I kept going with the taxi tests and then flying.

I do have to say I had numerous problems with the delivered engine some of which are documented elsewhere in this blog. Compression were very poor (although to be fair they were done on a cold engine) and it took a long time to get it tweaked so it would even start.

What happened next?
I did my first flight and another 30 hours of the test program. I had it starting on the first try for a while but it became progressively more difficult. The last few flights needed 3 tries to get a start. Finally I just could not start the engine at all. The tightness when pulling the prop through had continued as a major concern to me. It wasn’t right but I was flying and it seemed to run well once it was going. The fuel map was all over the place but that can be tweaked manually.

With the no start I did another 6 teeth on the flywheel and had to get the ring gear replaced. Ouch. I had some great advice from a USA engine guy and tweaked the timing to ensure zero TDC (top dead centre)  for the start. All back together it still would not start and this time I didn’t ‘push it’. The previous start failure had kickback which caused the damage. This can occur with the voltage low. My batteries are quite new and I have them on float between flights. I started pulling the prop through as a check and it was tight, really tight.

OK this might explain the no start. So much friction that I can’t get enough rotation speed? I had replaced the sparkplugs since the last attempt and this time they didn’t even get to fire. Here comes some videos so you know what I mean….

You can see how tight the prop has become (plugs in).

Here with the top spark plugs out we should have the thing spinning pretty freely. Nope it is still tight.

Of course the engine is cold because I couldn’t start it. I went for a ‘better’ video 30 minutes after the last one and the prop is now much looser. WTF???? I believe something has moved inside the engine given it now has reduced friction. Time for a look inside….

#1 Cylinder

#2 Cylinder

#3 Cylinder

#4 Cylinder   I’ve put a lot of photos up I know. Maybe someone will look at these and add some knowledge from their experience. Either way I have to do the obvious.

What Next?
With a no start and this cylinder inspection the decision was easy. The rust has increase enormously with flying and running the engine. It only used 1.5 litres of oil in 30 hours as well. The cylinders are just not getting lubrication. The oil rings are not doing the job and give the intermittent tightness something bad is happening deeper in the engine.

I have arrange for an engine shop to do a ‘bulk strip’ if required. Unfortunately they can’t look at it for a couple of months. That does give me time for removal and transport. It’s about 5 hours away by car and there are some logistics to deal with of course. Once we have a complete inspection we will know what needs doing and go from there.

I was never happy with the engine as it was delivered. There were too many things pointing to problems down the track. Fortunately perhaps, the issue has occurred requiring very major work. On the other side of this I will move forward towards my goals with increased confidence in my ride.