Top overhaul

In 2016, five years into building my very own Long-EZ, I "accidentally" became JT’s latest proud owner.

 

Meeting JT for the first time

At the time it seemed like a good idea... Fly JT while building the other one, learn as much as possible and incorporate desirable changes to my own build, then resell JT after my project's first flight. So, after a what I thought was a thorough pre-buy inspection during which a couple of issues were discovered and corrected, JT followed me home.

 

One always buys a used airplane hoping not to run into too many issues, nevertheless issues always seem to have a way of finding you.

Oh boy!

So in 2017, after just one year of occasional flying, JT came down with a case of low compression in all cylinders that couldn’t be helped, no matter what we tried. Interestingly enough, JT never showed any signs of slowing down, but my A&P did not feel comfortable passing the annual Condition Inspection anymore.

Saying that I was bummed would have been an understatement. With roughly 800 hours on the engine, and a suggested TBO (Time Between Overhauls) of 2000 hours, I was horrified at the prospect of performing expensive invasive maintenance on my still new to me airplane.

It turns out that not all engines make it to TBO, and statistically speaking the ones that do are engines that are used very often, like flight schools’ engines. Looking at JT’s logbook it appeared that she flew an average of 50 hours a year since she was finished in 2003. That was a little disappointing, but in line with what most airplane owners experience.

The verdict for JT was a “Top Overhaul”, and it would not be cheap even doing most of the work myself under the supervision of my trusted A&P.

JT's last photos before work began

To better understand what I was getting into, I decided to buy two specific books, Mike Bush on Engines (Mike Bush 2018), and Sky Ranch Engine Manual (John Schwaner 1990, latest edition 2017).

Very interesting book on overhaul pitfalls

If you haven't read this book you are doing IT wrong

These books most definitely helped me understand what I was up against. I cannot say enough good things about both, and I wouldn’t consider working on an aircraft engine without the background information they provided. They scared the crap out of me, and made me very cautious about how performing even seemingly insignificant tasks incorrectly could be disastrous.

I would also dare to say that Mike Bush’s book should be mandatory reading material for all piston engine pilots, as it relates strongly to how to operate one’s engine. Yes… it is that good, and it is critical that you know what’s going on with your engine if you want that relationship to last.

If you have ever worked on a car or motorcycle I’d say this type of work is not any more difficult than what you have already experienced, with a couple of differences… 1) certain “aviation only” tools are required, and 2) everything you touch can potentially kill you.

About point #2, because of what I learned from these books, I decided to not reuse any fasteners, and go new on just about everything that needed to go back on the engine.

Cylinder flange bolt hole. Note the supercritical absence of paint. Why? Read the books!

Brand new hardware. These nuts are not symmetrical.

Case nuts are directional, but you wouldn't know it without reading the  aforementioned books.

Because cylinder removal is the only real opportunity one has to asses the health of internal parts like the super important camshaft, I made sure to have plenty of expert eyes on it, and luckily for me JT’s was in good shape. The alternative would have meant a complete rebuild, something that was definitely not in my 2017 budget.

As always good friends are better than gold, and I relied heavily on the advice of Jim Parkman (owner of KCPK’s Epix Aviation), who helped me pick all the replacement parts I needed, and even trusted me to borrow some of his valuable calibrated torque wrenches to complete the most critical tasks. His advice and support are in large part reason for the success of this maintenance evolution.

Fun fact, this wrench used to belong to my previous employer Atlantic Coast Airlines.

I splurged afterwards and bought an identical torque wrench to Jim's from the Snap-On dealer ($$$$)

As for the cylinders I decided to go new, since the price difference was not as high as the peace of mind I'd get from them, and chose Nickel Carbide coated cylinders from ECI. Ironically, ECI was bought out by Continental Motors, so all of my Lycoming cylinders bear the Continental manufacturing logo.

New cylinder unboxing

The Continental logo made me pause for a second

Sleeping beauty

Pistons were already installed but had to come out for mounting

JT was originally equipped with a Lycoming O-320 E2A core and high compression pistons (160 hp), so I chose not change anything here and went with high compression pistons again made for the O-320 D2J version, so this did not change JT’s power output.

Lots of additional new parts to go with the new cylinders

Taking the piston out of the cylinder

Temporarily installing the wrist pin

JT now (2018) runs a O-320 E2A engine core with D2J pistons, although four years later (2022) this engine will become a fully fuel injected unit (IO-320), but this is the topic for another post.

Baffles, intakes, exhausts, starter, and alternator removed.

Cylinders #3 and #1 from above

Cylinders #2 and #4 from above

Cylinders #2 and #4 from below with intakes and exhausts removed

Cylinder #1 with the valve cover removed

Using my middle finger to push out the rocker arm and bushing

Rocker arms, and pushrods removed.

Removing the 8 bolts holding the cylinder with one of two special wrenches

Making sure #1 steel connecting rod does not fall and dent the aluminum case

Repurposing the used cylinder's orange silicone O-ring to suspend the connecting rod

Pushing out the piston pin, and plugs.

Letting the connecting rod dent the case would create oil leaks on the reassembled engine

Special tools make the job go so much easier

Aside from the lead deposits on top, this piston still looks pretty good.

Rings are still able to move, a little scuffing on the skirt perhaps.

Carbon and lead deposit, and signs of mild scuffing near the edge.

Obviously not new, but not as bad as I was expecting it to be.

From the look of things, these cylinders have been running hot for a very long time, evidenced by the burned paint and pink coloration in a few places. Unlike steel, aluminum slowly degrades with repeated heating cycles, and overheating can quickly weaken the structure of the cylinder head, and spell future disaster. This was one of the factors in my decision of going all new.

 

Pink by the exhaust port (right) is a definite sign of overheating

Here's a better look at the exhaust port

An overall look at cylinder #1

Looks like some more pink around the spark plug hole

 

Dirk (my trusted A&P) and I removed, examined, and replaced cylinder #1, after that I was on my own, though he came back to double check my work a few times. We did find a little scuffing by the pistons on a few cylinder walls, but never came up with a real smoking gun for the lack of compression.

 

After some cleanup

 

The plate allowed me to torque the case through-studs, preventing cranckshaft bushing rotation.

Valves looking very good

Moderate scuffing means contact... not very good.

More light contact... still not good.

Here's what a new cylinders looks like

Oil beads on smooth surfaces, cross hatching retains oil for lubrication.

 

The cleanest these valves will ever be

More new to old comparison

🤔... wonder which one is new...

Comparing the new cylinders to the old one to make sure everithing's the same

Found a few differences with the casting, but not enough to cause any problem.

Cylinder's top side

Looks like the paint was burned off near the spark plug

Overhauling these cylinders would've cost $900 vs $1200 for replacing them.

An extra $300 each for all new metal sounded like a good insurance policy to me

Dirk showing me how to install a new cylinder

All new nuts facing correctly, and properly torqued.

Cylinder #3 was the first one I replaced after Dirk showed me how.

 

Cylinder #3

Not sure if this was rust or burned oil residue

Cylinder #3 removed. Installing the torque plates.

Used silicone O-ring preventing connecting rod damage

Two down, two to go.

 

And... I forgot to take final photos of cylinder #3, but I did get photos of cylinder #2 coming out, and going in.

 

Here I am removing cylinder #2

Removing the piston pin

A closer look

I never let any of the connecting rod ever touch the engine case

Time to install the torque plate

Torque plate installed, and silicone cylinder O-ring holding the connecting rod.

A few days later the plate is off, and the new piston goes on.

Compressing the rings before cylinder installation

Installing the cylinder solo is doable, but another set of hands would have been helpful.

Pushrods inserted (blue ziptie for intake, red for exhaust). Yes... I removed the zipties later.

One thing I never knew before this experience is that there is a silicone O-ring at the base of each cylinder sealing the steel part of the cylinder against the aluminum engine case.

 

A new silicone O-ring installed at the base of the cylinder

The valve rockers were cleaned up, and sent to an overhaul shop to be inspected. They were found to be within specs so I reused them, although I replaced all of the rocker bushings. Interestingly, oil climbs through the hollow push-rods under pressure, transfers through a hole in the rocker arm and a matching hole in the bushing, and lubricates the rocker bushings. Needless to say putting the wrong bushing on the wrong rocker arm blocking the oil passageways would quickly lead to disaster.

 

Worn valve rocker bushing. A good reason to go all new.

Old rockers with new bushings. Highlighting the hidden oil passages.

#1 and #3 completed

#2 and #4 completed

At the opposite end of the pushrods sit the hydraulic lifters. These were cleaned up and reassembled.

 

Hydraulic lifter

Valve clearance is managed by replacing the hollow push-rods with longer or shorter ones as needed to achieve 0.028" to 0.080" of clearance. I had to buy a couple of new push-rods and move a few more around to achieve the desired result.

 

 

 

How to check valve clearance

Clearances (green), pushrod size (yellow).

I stripped the paint off the valve covers, lapped the mating surfaces on a machining grade granite plate, repainted the outside, and used new cork gaskets before closing the top ends of the cylinders.

 

Valve covers repainted

Meanwhile, with the engine partially off its mounts, I was also able to remove the one magneto (Left) and have it sent out for the overdue (non-mandatory in an experimental) 500 hours inspection/rebuild.

Left magneto. Note the lack of clearance from the firewall needed for removal.

Had to partially remove the engine to get this guy out

Magneto parts that were replaced during the inspection

I also took this opportunity to remove and replace the engine rubber shock mounts (Lord mounts), another expensive but much needed item.

Supporting the engine to replace top rubber shock mounts

Top right engine shock mount

This one didn't look too bad

A set of four brand new shock mounts

Here's why you should check them

Shock mount goes between the engine case (gray), and the engine mount (white).

Another mount that needed to get replaced

Bottom left mount

Bottom right mount

Top left mount

Top right mount

 

I did not trust any of the old rubber hoses not to leak after 15 years of service, so I bought new cylinder head oil drain rubber hoses, and new air intake hoses.

 

New drain hose ends

Oil drains from the valve cover area back to the case via aluminum tubes, and rubber hoses.

#1 and #3 oil drain tubes and hoses installed

#2 and #4 oil drain tubes and hoses installed

Old air intake rubber hose connector. All four were replaced.

 

Looking back at pictures I took of the air inlets to the head cooling baffles, the gap that admitted air to the cooling fins appeared to be very small. This certainly contributed to the cylinders running hot. It turns out that the only directions builders had at the time were related to the original O-235 engine, and not the O-320 engine Terry and many others started mounting on Long-EZs around the turn of the millennium. With more power came more heat to dissipate, and the original baffling proved to be insufficient. In JT's case this caused the CHTs to run hot for over fifteen years, and the evidence of excessive heat I discovered on the cylinders starts to make more sense now.

#2 and #4 small cooling air passages

Small #2 cooling air inlet

Small #4 cooling air inlet

Small #3 cooling air inlet

Small #1 cooling air inlet

I decided to open up both intake and exhaust slightly, based on later research papers that were not available at the time Terry built JT.

 

I also wanted to reduce the rattling and premature wearing of the baffling material, so I used silicone baffling material glued to the aluminum baffles.

 

Original baffles were metal on metal, and wore out.

Added silicone baffling material to prevent metal on metal contact

Silicone added to all baffles

Upgraded baffle installed

More baffle TLC in the rear

You get the idea

Eliminating rattling and wear is the name of the game

Baffles for #2 and #4 installed

Baffles for #1 and #3 installed

Because Terry did such a great job making a very tight cowling, the proximity of the exhaust pipes had been cooking the fiberglass in a few spots for some time, so I put a thermal barrier to reduce future problems.

 

Can you spot the hot areas on the bottom cowling?

 

Upgraded the thermal barrier (bottom = old, top = new)

Thermal barrier

I used RTV sealant to glue the barrier to the cowling

The main two areas that were very close to exhaust pipes

Bottom cowling ready to go fly

The exhaust came very close to the fiberglass here...

...and here.

Top cowling had a few hot spots as well

I also ended up adding some silicone baffling material toward the back of the cowling to reduce cooling air pressure losses.

 

Adding silicone baffling material to help seal the top cowl

With the cowl on, this was an open hole for cooling air to leak out.

Now the hole is closed, and the cowl can more easily pressurize in flight.

Had the same issue on the left side

Left side fix

Fix seen from the propeller

While I was at it, I also insulated the electronic ignition coil wires.

 

I think the possible issue is quite evident here

Heat shrinking the ignition wires made me feel much better

Once the engine was back together, we followed Lycoming pre-oiling procedure (Service Instruction No. 1241C) then performed the thankfully unexciting first engine start, after which I concentrated on getting JT ready for first flight.

 

Uneventful first engine start (fire equipment and personnel off camera)

 

 

Breaking in the new engine was done by the book (Service Instruction No. 1427C), and JT has flown roughly 140 trouble-free hours since then.

If I could add one word of caution for those doing the breaking-in of a new engine, it would be to not take off with high cylinder head temperatures (CHTs). I'd consider anything above 370º to be high while on the ground. Personally I'd shut down the engine instead, let it cool a bit, then restart and takeoff while the CHTs are still relatively low.

With so many new internal parts lapping themselves as the engine runs, it is possible for the CHTs to get pretty high on the ground, and getting airborne only to find out that you are already over-temping the engine (above 440º for Lycoming as per Mike Bush suggestions) while still low to the ground, requiring to pull the power way back, or even return quickly for an unscheduled landing.

 

Shutting down the engine on the ground will cool down CHT’s at a rate of approximately 20º/min, so even a 2 to 3 minutes pause will yield big dividends on the first flight, and you’ll be able to run at full power longer before reaching the CHTs limit (if ever). This will enable you to get away from the ground faster, which by itself increases the safety margin immensely, and creates more options should anything else go sideways.

 

After flying JT for some time, I started experimenting with incremental modifications to the lower cowl ramps in order to even out the CHTs among cylinders. Cylinder #2 (rear right) was running hotter than the rest, so I allowed some air to bypass the lower right ramp, to increase the amount flowing to the back of the airplane. 

Cooling ramps for cylinders #4 and #3 before modification

Holes added to cool down #2, and warm up #4.

The slots achieved the desired result, and the CHTs evened out.

In conclusion, this was a very expensive lesson to learn, and definitely one class I wouldn't have wanted to enroll in. In the end though I was happy to have been able to learn how to do this type of work. This experience will definitely make the connection between JT and me much deeper, and a lot more personal going forward.