Lycoming IO-360-A1B6D overhaul due to cracked case.

This engine came from a Cessna Cardinal RG belonging to a friend.  I've flown this plane in the past.  Nice plane and good engine that had a little bit of a vibration in it.  That was compensated with a dynamic balance of the prop, but those stresses take their toll.  I can't say that was the cause, but the engine started leaking oil through a stud on #1 cylinder.  A shop in Oregon investigated the oil leak for him and found the case was cracked through the left lower stud.  My friend removed the engine and brought it to me.  The engine is over 1000 hrs since overhaul and has a pretty significant oil consumption even before it started leaking oil.  My recommendation was that as long as we have to pull everything out of the case anyway, and it is clearly due for some cylinder work, let's go ahead and complete a major overhaul.  In that event, it is unlikely he will ever have to deal with anything major on the engine again.  We'll make decisions on where to send things depending on what we see and how things measure when we tear it down.  

11/18/2024 - Here's why it's in my shop.  This is the engine case just behind #1 cylinder.  Note the crack coming through the case just behind cylinder base stud.  A closer examination below shows that crack runs up the casting along behind the cylinder.  This case wasn't far from total failure.  I don't think this is one DIVCO would fix.



Sorting trays all laid out to keep things organized.

It arrived with Cyl #1 already off.

I put Will Pendergrass to work tearing down the engine with some assistance and supervision on my part.

He's about got it.  Not much more to do but split the case and start measuring parts.  Oh, and a few days of degreasing and bead blasting parts.

End of the day, here's the engine stacked on 3 tables.  Those big ears on the side of the crankshaft are floating counterweights to help smooth out the engine.

The news on the internals was a mixed bag; mostly good.  The cam and cam followers are in good used condition and will be sent to a machine shop for regrind and hardening.  The crankshaft is in good condition, but the main journals are at minimum for new spec and the rod journals are worn a bit beyond minimums.  So, the crank will have to go to a shop for regrinding.  We will also have the crank rebalanced.  The connecting rods are going to Santa Fe to be checked for measurements and balancing along with the wrist pins and cylinders for honing and valve work.  The cylinders appear to be in good condition, but were not new when installed, so this is the second run on them.  We'll have to see how they measure.  The exhaust valves will likely show enough wear that it will be time to replace them and the cylinders will need exhaust valve guides for sure.

One interesting thing I found.  I don't know if someone had attempted to replace the front seal on the engine or it had been assembled this way, but they had used the split front seal rather than the stretched seal.  That is actually an acceptable way to install it if you have to.  But, they had also failed to install the garter spring, which is the spring that goes inside the seal from the back to create some pressure to hold the lips of the seal on the crankshaft.  It also serves to align the seal halves when the seal is split like this one was.  Never-the-less, it wasn't leaking a lot of oil from it.  It is truly rare for me to tear down an engine and not find something wonky inside it from the original build.  

11/19/2024 - I didn't write an update today.   I simply forgot to take any pictures.  We spent all day cleaning parts and bead blasting the lead deposits out of the cylinders.  The crank, cam, and cam followers are all packaged up and ready for Larry (the owner) to drop off at Aircraft Specialties for machine work.  The cylinders, connecting rods, and wrist pins are all packaged up and ready to go to Santa Fe for honing, valve guides, and valve and seat grinding, and balancing of connecting rods.

11/20/2024 -  All the case parts, bolts and nuts in the left tray.  The accessories in the back tray.  And all the parts for the cylinders in the front trays.  This stuff goes on the shelf while the rest of the engine is making its way through various machine shops.  When I start building the engine, this stuff comes back out for cleaning before installation.  Note the rocker arms laying in the trays.  Yes, those are roller rockers, so roll on needle bearings on the shafts rather than bushings and have a roller over the end of the valve to avoid side loading the valves when they open.  I found 3 of the rotator caps that sit on top of the valves were not rotating, so the roller rockers had worn grooves into the caps.  They will need to be replaced.  I'll try to get a photo of that before it goes back together.  Also note the pushrod tube on the far right.  That's #4 exhaust pushrod.  The cylinder base nut next to it was overtorqued and I banged into the tube denting it when the base nut popped loose.  I was able to force a 5/8" dowel rod down through the tube to push the dent out of it so the push rod won't drag and wear a hole through the tube from the inside.

Cylinder after bead blasting.

The exhaust and intake ports after bead blasting all the lead salts out of the ports.

Inside of the cylinder heads after bead blasting.

Valves following bead blasting and cleaning with a wire wheel.  Each baggy has the valve keepers, springs, retainers and valves.

11/22/2024 - No pictures to post.  We searched the local hardware stores for the "right" shade or red paint to match the red Cardinal the engine came off.  No luck so far, so may have to go to the local auto paint store and have them match it.  The owner went to a local paint shop and had them do a color match.  Theymixed some matching paint and put it in spray cans for him to use, then sold him some Y2K PolyUrethane Clear Coat.  It does look nice, but I'm not enthusiastic about spraying polyurethanes in the hangar, and especially without a respirator.  Since it was a nice day, he did the paint work outside.  Yes, I have respirators, but he opted not to use one outside.   

The internal parts from this engine will be going to Aircraft Specialties for overhaul.  My gripe with Aircraft Specialties is that they will almost always grind down a perfectly good crankshaft, whether it needs it or not.  That pads the bill for their machine shop services, but they may also do that for liability protection.  I haven't had any problems with their finished work.  When I measured the crank on this engine, the mains measured just outside of new limits and the rod journals measured .0015" under the limits.  Since it needs to be reground, the crank will go to Aircraft Specialties for regrinding and balance.  The camshaft and cam followers are in good condition, so will also go to Aircraft Specialties for overhaul.


Overhaul process for aircraft crankshafts:  
Regrinding an aircraft crankshaft is significantly different from regrinding an automotive crank.  These cranks are nitrided, so are very hard.  That doesn't make a big difference to grinding, but does affect the process as they need to go through a Nitriding process.  

When the machine shop gets the crankshaft, they always dimension the crankshafts.  They measure each bearing surface in at least  two directions to check for wear.  Then measure the crank flange for runout (or wobble).  The measure the center main bearing for runout (straightness of the crankshaft).  If the crankshaft meets minimium specs to be reground, they grind each journal to spec.  On a Lycoming, they can be ground .003, .006, .009, .010,  .012, and .015 undersized.  Continental  uses .010 and .020 undersize bearings, then it's time to retire the crankshaft.  The rod journals will always be ground to the same undersize and the main journals will always be ground to the same undersize.  But, the rods and mains may be ground to different undersize depending on the condition of the crankshaft.  I had one recently that came back with the Mains ground .006" undersize and the rods ground .003" undersize.  One thing that is different about an aircraft crankshaft is that there are not cut edges on a journal.  Every crankshaft I have seen has a minimum radius of 3/32 of an inch at the edges of every journal.  A sharp edge is a stress riser and will cause the crank to fail.  I've seen one aircraft crankshaft an owner re-installed that had one rod journal that was cut with a sharp edge.  The crankshaft broke at that journal with the crack starting at that sharp edge causing an emergency forced landing in with the plane and proving to be very costly to the owner as the plane was grounded  800 miles from home while an unknown shop overhauled his engine.  The shop may balance the crankshaft at this point, but that is optional and very few crankshafts get properly balanced.  I almost always pay to have the crankshaft balanced.  Most people do not.  But I love a smooth engine.  It is surprising how much they grind off a crank to balance them properly even though it may not necessarily have been a rough running engine.  Once balanced, the crankshaft waits for the shop to do a weekend furnace run.  The shop puts a batch of crankshafts into a furnace where they are heated in an agitated ammonia or nitrogen atmosphere to a temperature between 450 and 600°C.  The furnace temperature is ramped up slowly, then held at temperature for an extended period of time.  The nitrogen reacts with the alloying elements of the steel at the surface of the crankshaft creating the nitrided surface that runs roughly .030" deep into the metal.  The nitrided surface is very hard and resistant to wear and fatigue.  Following the furnace run, the crankshaft goes back to the machine shop for pollishing.  The crank is cleaned once again and the crank journals are polished with an abrasive belt while turning in a lathe.  Once polished they are measured again for dimensions.  The crank has one last stop to make over in the plating shop.  In the plating shop, just the front of the crankshaft (flange and front seal surface) are dipped into a vat for electro-plating with cadmium for corrosion resistance.  Once plated, the crankshaft is ready to be shipped back for return service.  You can see the previous cad plating on this crannkshaft in the photo above.  This crankshaft has been overhauled once before and was run a second time with the journals polished at standard size.  Now they are showing some wear and will have to be reground to under size.  

It's worth noting that this crankshaft has "free floating" counterweights between #3 and #4 rod journals.  The counterweights are on pins and actually move around on those pins.  The weights are there to smooth the engine.  If you think about it, this is a 4 cylinder engine with the same displacement as a truck engine.  I am aways amazed that they can make their horsepower as smoothly as they do.  During the overhaul process, the counterweighs are removed and cleaned.  The mounting pins may be replaced.  There is also a dowel pin at the back of the crank that is used to index the gear that drives the accessories.  That dowel pin is always removed and replaced.

11/25/2024 - The new engine case sitting next to the old case.  We still need to move some plugs, fittings and oilers between the cases.  But gosh, isn't that new case pretty?

Masking off the new case half getting ready for paint.  It should probably be noted that any surface where a bolt seats that requires a critical torque must be paint free.  Specifically, that is where the cylinder and case studs and throughbolts are torqued down.  Additionally, any surface you expect to seal also needs to be paint free.  That is why you see a bolt and washer covering the holes where the bolts seat in the front collar of the case as well as masking over the pushrod tube seats and cylinder seating area.

Painted Cardinal red to match the plane where it will be mounted.

I asked,  "Why the yellow sump?"  Well, 'cause it was already yellow and was easier to repaint the same color.

Masking removed.  Bolts and washers were still in the front collar holes.

Case halves zip tied together for storage and the masking removed from the case halves and accessory case.  It is pretty!  Now it goes on the shelf for several weeks until we get the crank, cam, cam followers, connecting rods, wrist pins, and cylinders back.  We'll also be ordering new pistons, rings, bearings, and all the other associated overhaul parts once we know how far undersize the crank gets ground.

12/3/2024 -  Crank, cam and cam followers were delivered to Aircraft Specialties today.  They estimated 6 - 8 week turnaround.  If so, we'll be building this engine in February.

1/15/2025 - Parts are starting to arrive for this engine.  The crank was turned down M003, .003" undersize on both mains and rod pins.  The crank and cam followers (tappets/lifter bodies) should be shipped this week, but I don't have them yet.  The cam failed to make spec, so a new camshaft was purchased.  The valves and valve guides all meet spec, so the valves and seats were ground and cylinders honed.  All the overhaul parts should be arriving with FedEx this morning.  I'm finishing the center section tank for the Biplane, then will get started building this engine probably the last week of January or the first week of February.


2/1/2025 - The crankshaft is here and it is a piece of art!  The first thing I do to is is take some emory cloth and scuff a helix into the cad plated surface just behind the prop flange.  The front seal doesn't necessarily seal very well on the cad plated surface, but scuffing a helix into it so when the engine is running the helix draws any oil wanting to weep through the seal gets drawn back into the engine.  This trick is from a Continental service bulletin, but I find it works quite well on both Continental and Lycoming engines.

The first order of business was to inspect the new case.  I called a halt to the build first thing as until I got more clarification.  Notice any difference between the new case above and the old case below?

The old case has an "O" ring around every stud and through bolt that goes through the case.  Look at the upper photo of the new case again.  The center and front "through bolts" have no relief cut for an O-ring.  First I checked the parts manual.  My parts manual only calls for the small set of O-rings at the front of the case and the larger set of O-rings around the back studs at the back main bearing.  The other two aren't shown, but it's a lousy drawing that doesn't show the inside of the right half of the case, so is less than clear.  So, I called a friend that had recently overhauled the exact same model engine.  He sent me photos of his, which also has a relief cut for O-rings at every stud.  Is this a machining error?  Or is it a revision?  I know Continental does not use an O-ring in this position, but I've also seen a lot of case leaks on Continentals at the through bolts.  This is the beauty of having another mechanic here on the field that has also done a lot of overhauls.  We discussed it and agreed that this is a newer revision of the engine case and Lycoming must have decided those O-rings were unnecessary.  It doesn't make me feel warm and fuzzy, so I'll use a bit of Hylomar and silk thread around the 4 through bolts to ensure as best I can that they don't leak.  OK, this mystery is resolved to the best of my ability for a Saturday.  On to assembling the engine!

Later when I installed the through bolts, I found they were an interference fit, so the likelihood of them leaking is significantly reduced.  The through bolts were not an interfenence fit when I removed them from the old case.  If they were at one time, they weren't anymore as they came right out with a gentle tap.

Time to get started with the assembly of this engine.  At this point in time, I have the front seal already mounted on the engine.  That front seal is not a split seal.  I remove the spring from the lip of the seal and put it back together on the crankshaft.  I boil the seal in water in the microwave, then stretch it over the prop flange while it is warm using a selection of tire spoons to avoid scratching the crank flange.  Once it is over the flange, it quickly shrinks back to shape and I insert the spring into the back of the seal.  It is always a struggle to get these on, but it always works.  It took three attempts to install this seal before I could get the leverage to stretch it over the flange.  We did a video of installing the seal, but the struggle is real and the language may not have been appropriate for broadcasting.

At this point in time I am putting Lubriplate (TM) Assembly lube on the rod journals in preparation to install the rod bearings.

Rods are installed on the crankshaft, but the rod bolts are not torqued.  Rod bolts and nuts are always replaced on overhaul.

A torque spec on these rod bolts does not exist.  You tighten them down until the bolt stretches to meet the length specified in the overhaul manual.  In this picture, I'm using my 2 - 3" Micrometer to measure the rod bolt length.  I torqued them to 30 ft lb, then stepped them up at 5 ft lb increments until I got the proper stretch.  In the case of this engine, that worked out to be at exactly 50 ft. lb. on my 1/2" torque wrench to make the minimum stretch.  I had written in my manual from a previous overhaul that it was 53 ft.lb., which would have still been within the stretch spec for this engine.

Inserting the front bearing that takes the prop loads.  This bearing is split at the top and bottom in this picture, or at the 90° and 270° positions when the case is sitting in the plane.  The bearing has to be installed onto the crankshaft, then the crankshaft carefully placed into the case while aligning the front bearing onto the alignment dowels by feel as you can't see them under the crankshaft.  It is really easy to put them in and miss the alignment dowels (yes, I did that on my own engine!)  In order to ensure that the bearing is fully seated on the alignment dowels, in this photo I have the bearing in place and am marking the sides of the bearing with a pen along the edge of the case.  When I install the crankshaft with the bearing on it, if the lines drawn on the bearing are not fully seated to the edge of the case, then the bearing is not properly seated onto the dowels.  If you tighten down the case with the bearing not properly seated, you have just damaged a very expensive bearing.

Notice the large flat area in the case just aft of the front bearing in the photo above.  That is the thrust bearing surface for this engine.  Yes, Lycoming has a machined face in front of the #1 rod throw that rides against a machined aluminum surface in the case.  That's what you are pulling against all the time when flying behind your Lycoming engine.  That's not a critisizm as it clearly works.  This isn't a machined surface that getsfilled in and recut when a case or crankshaft is overhauled as that would leave an unacceptable amount of end play in the crankshaft, and there are a lot of Lycoming engines out there with 6000 or even 8000 hours on the case that have been through multiple overhauls.

Setting the camshaft into the right side of the case after lubricating the camshaft bearing surfaces with assembly lube.  The cam followers are already installed under the camshaft with the faces of the tappets lubricated with Moly/Zinc Cam break-in grease.  Note the big hole in the middle of the front saddle where the front bearing sits.  This is the oil transfer port where the prop governor transfers oil through the front bearing into the center bore of the crankshaft to control the prop pitch with oil pressure from the governor.  The black stuff on the face of the cam followers below is the moly/zinc break-in grease.  Each cam lobe was also coated with this grease before the case halves were mated together.

The crankshaft is installed into the left half of the case with the front bearing seated onto the alignment dowels.  The large hole beetween the two halves of the bearing shells aligns with the oil transfer port in the right case half.  In this photo, you can see the oil transfer port also aligned on the crankshaft.  The bearing supports the crankshaft at the front and back of the bearing face, and has an area between the two supports for the oil transfer port.  So, the crankshaft is completely surrounded with pressurized oil inside the bearing shell so oil transfers to the prop all the time, not just when the port aligns with the hole in the bearing.  The prop governor is regulating the pressure at that hole in the front bearing and can run as high as 410 psi.  That is why the oil transfer line and fittings from the governor to the prop hub are required to be steel or stainless steel.  

Painting the left side of the case with Hylomar Blue sealer.  That little bottle of sealer is about $100.

Laying silk thread into the sealing surface of the left half of the case.  You can see in the background that I have both surfaces painted with a thin coat of Hylomar.  The manual only calls for coating one surface, but I find that I get no leaks with this method.

I'm putting a bit of silicone sealant on the outer flange of the front seal, then will push the seal into place.  This is the only place silicone sealant should ever be used in an aircraft engine.

The left half of the case has been mated to the right half of the case.  Note the little pieces of safety wire tied around a couple of cylinder base studs.  That is some .020" safety wire that is wrapped around the camshaft to hold it into the right case half while lowering the right half down onto the left half.  With the cam trapped into it's bearing blocks, it also holds the cam followers captive into the right half of the case.  You can gently lower the right half of the case onto the left half without having all the parts falling out.  Once in place, you snip the safety wire and pull it out.

Also note above that the through bolts are not installed yet.  That's why there are two studs missing at the front of #1 and #3 cylinders on the case.

The engine goes onto the stand for further assembly.  Note that the through bolts are in the case at this point in time.  We polished the heck out of the bolts and still found them to be a quite snug interference fit.  They had to be driven in with brass drift and 2# hammer.  It would be kinder for the through bolts if I did this with a lead hammer... if I owned one.

Fuel divider and a few other goodies getting installed onto the case.  Oil temp thermocouple is screwed into the front of this case.

The case bolts are all torqued in and the 3 internal bolts safety wired.

And that pesky castilated case nut that's hidden under the cam gear.  Lots of people tell me about building a special wrench to get to that nut.  You can actually get to it with a tool common to every aircraft mechanic's tool set.  The 9/16" cylinder base wrench will do it.  That little bit of scoring under the nut was my action with a punch trying to get at the cotter key to bend the tangs on it properly.  

The cylinders are all painted and ready for installation on Monday.  That's going to smell funny on the first run of this engine!

2/5/2025 - Installed all the cylinders.  This particular engine has roller rocker arms installed on it.  I've never seen them in a Lycoming engine before, so have to look for an adverse effects or wear caused by them.  The back two cylinders don't have the rockers installed.  The explanation is below.


And there it is.  The valve rotator caps rather than rotating as they should under a standard rocker arm, have a groove worn into them from the roller on the rocker arm.  I had spotted the top three previously and had new caps ordered to replace them.  But upon closer inspection this morning, I found three more than were showing a small amount of wear that was only visible when light was reflected against the top surface.  I put the assembly on hold and ordered more replacement rotator caps.  They should be here on Thursday.

This is the roller rocker arm used in this engine.  While it caused some wear issues with the valve rotator caps, the concept of roller rockers clearly works.  This engine had 1000 hours since it was last overhauled.  The valves and valve guides, including the exhaust guides, still met new spec and did not require replacement.  I have never seen a Lycoming or Continental engine that didn't need new exhaust valve guides by 1000 hours.  This one did not.  These are kind of a bugger to install with needle bearings and thrust bushing both inside and on the side of the rocker arms.

While waiting for the valve components to arrive, I decided to assemble the gear train in the accessory case instead.  This was a test assembly, then the gears were removed and cleaned, then reassembled and packed with assembly lube before installing the accessory case.  In order from the top to bottom, the gears are Camshaft, Cam idler gear, to the left is the magneto drive gear/coupling, and below that is the idler gear that drives the prop governor.  The gear that is laying on it's side is the vacuum pump drive gear.  The oil pump drive and prop governor drive are missing as they are installed in the accessory case.  The vacuum pump gear will also be installed in the accessory case before the accessory case gets installed onto the engine.  The long shaft that is sticking out of the cam gear below is the tachometer drive shaft.  It sticks out through the accessory case through a bushing and seal where the tach cable gets plugged into the end of the tach drive shaft and screwed onto the tach drive on the back of the accessory case.  This engine was part of Lycomings "76" series engines, designed to be simpler and less expensive than the previous engines.  They were neither.  However, they used a single drive dual magneto, which turned out to be a terrible idea and created a single point of failure for the ignition systems.  They are reliable, but have now been disowned and new production ceased by Bendix, the owner of this magneto design.  Now you can only get them repaired, but not replaced.  We considered changing this engine to the more standard dual magneto setup during overhaul, especially since we were replacing the engine case.  But the cost of a different accessory case and all the internal drive gears was prohibitively high.

Gears in place, on the back of the engine.  The gear seating lubricated for gears in the accessory case to seat into.  The gasket is in place and painted with Hylomar.  Below, the oil pump is assembled, packed with assembly lube and bolted into the accesory case.  The vacuum pump drive gear is installed at the top and the prop governor drive gear is installed at the bottom.  The fuel pump push rod is in place in the sleeve in the center or the accessory case.  It rides on the eccentric cam that is built into the camshaft idler gear above.



Accessory case is installed with the gears well lubricated with assembly lube.  This is a look up inside from the bottom.

Accessory case installed and torqued down.

This is the ball and spring that goes inside the oil pressure regulator.  In this model, you remove the regulator and add a washer behind the spring to increase the default oil pressure.  There is another model avilable that you can just turn an adjustment bolt in to tighten the spring and raise the oil pressure.  The two models are interchangeable.

The oil pressure regulator screws into the case just behind #3 cylinder, then gets safetied into place.

Oil filter canister, fuel pump and prop governor installed.



2/7/2025 - After a week of FedEx Ground losing parts and shipping them to the wrong end of the country, Air Power overnighted us the replacement parts.  Yes those three little rotator caps from a few pictures up have held us at a standstill all week. This afternoon we could finally get back to work.  Now the cylinders are mounted and the intercylinder cooling baffles are installed.

A word about Air Power for parts.  Their prices are lowest I can find.  There is no tax on the parts.  And Fed Ex Ground shipping is free.  Overall, I save about 25% by buying my Luycoming (Superior) and Continental parts through them.  The fiasco this week was not their fault, but the ineptitude at FedEx ground.  Air Power overnighted me a second set of parts at no charge and will settle up with me once FedEx actually finds and delivers the parts that were supposed to be here two days ago, then they will have them shipped back to them.  Now that is service, and I am very pleased with them.

Intercylinder baffles shown from below.  These force air around the bottom of the cylinders and cylinder heads to help them cool.  Also, the oil drains for the cylinder heads are now installed.

The fuel injectors are installed into the heads and fuel injection lines are on, with my disassembly labels still hanging on them  I still need to put all the adel clamps onto the injector lines to support them.

Oil tank and intake runners are now installed.

Fuel injector line supports are in place now.  There are still a few more things to go back onto this, but I hope to complete this engine tomorrow and get it loaded into the shipping crate to head back home.

2/8/2025 - Fuel servo and all the plumbing installed.  The engine is complete and time to clean up the shop.

Engine is on the hoist and headed into it's crate for the trip back to Oregon.  Bye, bye...