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Titan 0-340 Burnt Intake Valves

Mike Macon

Well Known Member
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Does anyone know of issues with intake valves on the 0-340?
Does anyone besides Titan make replacement cylinders?
 
Intake valves rarely burn,per se,but they may be leaking from being poorly seated on assembly.
Or a pushrod length problem.
 
I had one burnt intake valve on a Titan 320 cylinder a few years back. A local cylinder shop replaced the valve and reground the seat.

The 320 and 360 use the same valves and seats. My guess is the 340 will also. A local cylinder shop should be able to fix your valve issue.

My guess is that your push rods are an incorrect length. After the rework, my guess is that they will be even longer than they should be. My intake valve that burnt had valve lash clearance at 0.028" when it was assembled. Spec is 0.028 to 0.080". It was in spec but right at the minimum acceptable. I would hope that push rod change would have clearance between the two extremes.
 
Gary - This is my second one. #1 cylinder at 600 hrs. and now #4 at 650 hrs. There is a definite burn mark at the valve head edge. I used to be a little better at posting pictures to this site and I will work on that. CubCrafters replaced the first cylinder after me and a mechanic gave up chasing what we thought was an ignition issue because it only missed on one ignition. Ran fine on the other. They had never seen a burnt intake valve before mine. They chased the ignition for awhile also.
I have only found one similar burnt valve issue with the 0-340 on the internet and his picture was identical to mine. I was just curious if there were any more similar issues out there or am just I just the only unlucky dude. Also curious if anyone else makes replacement cylinders besides Titan for this engine.
 
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I am not aware of anyone making cylinders for the 340 other than Titan.

As I understand it, the 320, 340, 360 all use the same head, head parts, and bore but have a different stroke. The different stroke requires a different crankshaft, connecting rod, and cylinder barrel.

My #2 cylinder was 74/80 (all others 80/80) @ 709.9 hours TIS. Ran it another oil change and at 739.2 hours TIS, it was 67/80 so I pulled it knowing intake valve leaks do not get better. The cylinder going back on the airplane did require a shorter pushrod. Intake Valve lash with new push rod was 0.031" with spec of 0.028-0.080".
 
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Gary - This is my second one. #1 cylinder at 600 hrs. and now #4 at 650 hrs. There is a definite burn mark at the valve head edge. I used to be a little better at posting pictures to this site and I will work on that. CubCrafters replaced the first cylinder after me and a mechanic gave up chasing what we thought was an ignition issue because it only missed on one ignition. Ran fine on the other. They had never seen a burnt intake valve before mine. They chased the ignition for awhile also.
I have only found one similar burnt valve issue with the 0-340 on the internet and his picture was identical to mine. I was just curious if there were any more similar issues out there or am just I just the only unlucky dude. Also curious if anyone else makes replacement cylinders besides Titan for this engine.

I also would be looking at an ignition or other combustion issues. It is pretty uncommon to get burned intake valves, ESPECIALLY without the persence of burned exhaust valves. The intake valve runs much cooler than the exh for several reasons. Without a picture, I would speculate that something is getting deposited on the valve and that deposit is then burning. Burning deposits are not the same as a burned valve.

What is the oil consumption rate? What is the carbon deposit load on that cyl wall above the top land?

Larry
 
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Pics from O/P. Definitely looks like burnt intake valves. I speculated they started from a small angle error when the guide was reamed or possibly setup error when the valve face or seat face was ground. The slight leakage at the contact area would allow the flame to propagate just a bit past the seat into the intake chamber. Over time, that clearance would grow, from flame activity, to the point of allowing greater and greater heat retention in the valve at that area and the burning seen.

Larry
 
Thanks Gary. I know you were not a big CA fan but are you missing the left coast at all?

I miss my friends, I miss the scenery, and I miss the climate. I do not miss the congestion, I do not miss the high cost of living, I do not miss the regulations, and I do not miss the politics. More bad than good.

I have flown there commercially twice last year and once this year. Almost everything I saw as 140 to 150% more than what I pay here in North Carolina.
 
Also curious if anyone else makes replacement cylinders besides Titan for this engine.
As a new Titan x-340 owner I too would like to know this for future reference.

I am not aware of anyone making cylinders for the 340 other than Titan.

As I understand it, the 320, 340, 360 all use the same head, head parts, and bore but have a different stroke. The different stroke requires a different crankshaft, connecting rod, and cylinder barrel.
So o-320 cylinders wouldn't fit?

Can anyone confirm this?
 
Gary - This is my second one. #1 cylinder at 600 hrs. and now #4 at 650 hrs. There is a definite burn mark at the valve head edge. I used to be a little better at posting pictures to this site and I will work on that. CubCrafters replaced the first cylinder after me and a mechanic gave up chasing what we thought was an ignition issue because it only missed on one ignition. Ran fine on the other. They had never seen a burnt intake valve before mine. They chased the ignition for awhile also.
I have only found one similar burnt valve issue with the 0-340 on the internet and his picture was identical to mine. I was just curious if there were any more similar issues out there or am just I just the only unlucky dude. Also curious if anyone else makes replacement cylinders besides Titan for this engine.

I would bet on either poor sealing from the beginning (bad seat geometry), or push rod length or basically lash setting. I would expect that ignition would yield other issues long before it would burn an intake valve.

Now, this is assuming that the valve was new, and had a proper thickness from the beginning. A thin edged valve can still burn even with proper lash and seat contact area.

The fact that all cylinders are doing the same thing indicates it was built improperly and consistently in some way. It could even be poor metallurgy of the valve heads, but that would be low on the list of potential causes. Replacement of all intake valves would be required.
 
The rocker contact point is not centered on the valve stem by design.

I kinda question if lyc got that geometry right in the early design. Why else would they have added the rotator cap to the exh valve, if the geometry was set up properly to drive rotation. I assumed the offsets were built into that cap and not the rocker geometry. Why else put it there, where it forces the use of those compromised keepers.

Larry
 
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So if one was to use roller rockers on a Lycoming engine, all the valves would have a good chance of burning. Is that correct?

Not if they are made correctly. I have had rocker arms custom made and offset the valve stem slightly. As long as the pushing force is off to one side they will rotate.
 
A roller rocker has a small roller that rolls over the end of the valve stem. This virtually eliminates side load on the stem and greatly reduces wear. How does it rotate the valve.
 
A roller rocker has a small roller that rolls over the end of the valve stem. This virtually eliminates side load on the stem and greatly reduces wear. How does it rotate the valve.

side loading is mostly a function of angles/geometry and not friction. The roller is still a static plane, just like the flat surface of the old rockers. Change the angle of the bearing shaft from parallel to the valve stem face plane and you still get side load. There can be different side loads happening, not just the side load introduced when the rocker face is not operating exactly in plane with the valve stem, as it does through most of it's travel. Yes, in that particular case, friction is driving much of the side load in a flat faced rocker. I believe Bob is referring do a different type of side load, introduced by tilting the rocker shaft plane a small amount from the valve stem face plane.
 
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A roller rocker has a small roller that rolls over the end of the valve stem. This virtually eliminates side load on the stem and greatly reduces wear. How does it rotate the valve.

The roller rockers I made are simply offset a slight amount, just as are stock rockers. There is just enough sideloading to cause the valve, springs, keepers, and the spring seats to rotate. That is why the spring seat bottoms appear highly polished when removed.
 
Intake Valve Rotation

I’m a Lycoming guy and I question some of this. On Parallel Valve cylinders the exhaust valve has a rotator cap which actually releases the valve keepers as the rocker depresses the valve allowing valve rotation. The intake valves have no such device. On Angle valve cylinders many have rotator caps on the Intake valves as well allowing them to rotate. Rocket Bob May be right about the whole assembly ie springs,keepers,retainer and valve on the intake side rotating in the head but why doesn’t Lycoming simply put rotator caps on the intake valves like they do on some Angle valve engines ? I’ve noticed all the turbocharged angle valve engines use rotators on the intakes if that’s a reference point.

I would love to see something definitive in a Lycoming publication on the subject.

On the Titan 340 cylinders, they are unique and only work with the Titan 340 crank and rods. There is no equivalent in the Lycoming world.
 
The rotator cap is used on sodium-filled exhaust valves. I believe the reason is the weld that closes off the sodium chamber is not hard and would quickly wear without it. The rotator caps are stellite coated for hardness but they do wear. I'm not sure if it actually aids in rotation.

Here's a youtube I stumbled across (albeit a Continental) that shows the rotation.

https://www.youtube.com/watch?v=_UUvIDaWChA

The other possibility for the valve not rotating would be incorrect angles on the seat and/or valve face. The OH manual specifies a desired 1 degree included angle. If the angle goes the wrong way the valve can wedge in the seat and not rotate.
 
I was hoping someone would post on the cylinder barrow difference in the 0320 and titan X340 engine . Continental list the exp titan X340 as 32.27 wide , same as the 0320 . So not sure the X340 dose not use same barrow as 0320 ? They list the 0360 as 33.41 wide .
 
I think the valve spring itself creates most of the rotation of the valve. When the spring compresses and returns to normal, it has torsional movement that rotates the retainer, the keepers, and the valve. The valve spring itself may rotate slightly because of the inertia of the rest of the moving parts. Its really a random amount of movement that would be hard to regulate. No two valves rotate at the same speed. At least we can all agree that they do indeed rotate.

A good thing.
 
I think the valve spring itself creates most of the rotation of the valve. When the spring compresses and returns to normal, it has torsional movement that rotates the retainer, the keepers, and the valve. The valve spring itself may rotate slightly because of the inertia of the rest of the moving parts. Its really a random amount of movement that would be hard to regulate. No two valves rotate at the same speed. At least we can all agree that they do indeed rotate.

A good thing.

You need to look up the mechanism of how the positive rotators actually work. There are different designs and do not randomly rotate, they always rotate and a fixed amount. With NO rotator, the rotation is random and may not even occur, thus the reason for having positive rotators. Light duty engine seldom have positive rotators. Heavy duty always have them for predictable (longer) life. Aircraft propulsion is a heavy duty application.

I should have stated that, as Bob has mentioned, exhaust are the first to need rotators, then intake. Typically not on the intake esp. for NA engines. Since all are burning, it is like some design issue that could well be overcome with rotators. Many factors come into play for the determination from a design standpoint.
 
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I’m a Lycoming guy and I question some of this. On Parallel Valve cylinders the exhaust valve has a rotator cap which actually releases the valve keepers as the rocker depresses the valve allowing valve rotation. The intake valves have no such device. On Angle valve cylinders many have rotator caps on the Intake valves as well allowing them to rotate. Rocket Bob May be right about the whole assembly ie springs,keepers,retainer and valve on the intake side rotating in the head but why doesn’t Lycoming simply put rotator caps on the intake valves like they do on some Angle valve engines ? I’ve noticed all the turbocharged angle valve engines use rotators on the intakes if that’s a reference point.

Not all Lycoming valves have a rotator cap.
 
Parallel valve Lycoming valves don't have to rotate

I had a valve rotation discussion with Lycoming tech support in October 2017. Lycoming tech support told me (in the context of an IO-540-C4B5) that the rotator cap does *not* impart rotation onto the valves. The valves *can* rotate, but they don't have to.

Here's a good article on different types of valve rotators designs, including the (non-positive) thimble valve rotator, whose description matches the parallel valve Lycoming cylinders I've worked on:

https://marineengineersblogs.blogspot.com/2012/12/valve-rotators.html?m=0

Note that the thimble valve rotator design *permits* rotation (when the valve is open) but does not *impart* rotation.
 
The Aviation Consumer, around 10 years ago found that over 20% of new cylinders inspected had non-concentric valve seats with irregular contact. I believe these were factory Lycoming. They'd heard of many cylinders going soft in only a few hundred hours and seen leaking and burned valves on a number of these.

Their recommendation was to disassemble these new cylinders and check/ correct before putting them in service.

I'm not saying that's what happened here but most cases of burnt valves can be traced to hot gas leakage caused by improper seat contact or the valve being held open slightly for some reason.
 
Valve Rotation

Thanks Tim for a great article explaining how the rotator caps work on a Lycoming:
“Note that the thimble valve rotator design *permits* rotation (when the valve is open) but does not *impart* rotation”
I didn’t know that engine vibration was the force that caused the rotation after the caps release the valve. Not intuitive at least to me.
To Ross’s comments on the concentric problems of valves and seats even on new cylinders. When LyCon does their port-flowing of cylinder heads they also redo the valves and seats even on new cylinders using a Serdi precision valve machine that has an accuracy of portions of thousands of an inch. The contours of the valve and seat are responsible for a portion of the HP increase seen by their port-flowing. When I see an old fashioned Sioux grinder with arbor and grinding stones used by most cylinder overhaul shops I’m amazed at the operator skill and technique to get even a reasonably accurate job.


Back to the OP: Consider pulling your cylinders and having all the valves and seats redone by a shop with a Serdi machine. If Ross is right that might cure your problem.
 
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Duff -

I am sending the two cylinders with burnt intake valves, that includes the one that was replaced 50 hrs. ago, and the two that have not failed out for repairs and reconditioning to Aero Sport.
My apologies to Doug if they do not advertise here.
 
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Please note that the Continental SIL007 only refers to replacement cylinders for Lycoming(R) engines. The Lycoming 340 has a different diameter cylinder barrel. The Titan 340 has the same diameter cylinder barrels as a 320. The 320 cylinders CAN be used on the Titan 340. Most Titan 340 engines have tapered cylinder barrel fins to reduce weight and direct more cooling air to the heads and a venturi design intake valve seat. Other than those differences, the Titan 340 cylinder is the same as a 320.
 
340 cylinders

Thanks J B for piping in. I made a bad assumption about the 340 cylinder dimensions. After talking to a very knowledgeable source I learned that when using the 340 stroker crank they make up the difference in deck height with the piston ie a 7:1 compression piston ends up being something like a 9:1 compression ratio. They do this with a stock length 0320 rod but they do some extra machining on the large end to clear the crankcase.
So back to the OP: Factory Lycoming 0320 cylinders would be an option.
 
Thanks guys, that's the info I have been searching for and knew this website was going to be my best resource. VAF comes through again.
 
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