Sticky valve_Lycoming IO-360-A3B6D

[carusoam]

9201A,

Are you associating the aggressive leaning to the stuck valve?

LOP ops are known? for cleaner burning engines.

I was expecting fewer stuck exhaust valves if LOP were to be increased accross the Mooney family.

Then again, what is the the actual cause of the stuck valve? What does the rope trick clean out of the guides?

Carbon from oil cooked after shut down?

LOP would generate lower CHTs during flight, lesser opportunity for cooking the oil.

Honest questions, thinking out loud...

My C's stuck valve occurred after sitting for years, combination of carbon and rust???

Best regards,

-a-

[aaronk25]

Since we have this stuck valve thread, I might as well add my very recent stuck valve story.

I took my plane up to LASAR for the annual and it ran fine all the way there. I have never had the issue of "morning sickness", or any roughness on idle except after shut down and then a hot restart. I always just chalked that one up to just "a Lycoming thing". Anyhow, all was well until I pulled the power back in the traffic pattern at Lampson. It for the first time ever ran a little rough. Oh well, land the plane, go straight to annual.

First thing they do on the annual when you pull up is the compression test while the engine is still hot. Well, all the cylinders came up perfect except #1. On #1 they got zero compression. That was odd. It ran a little rough in the pattern, but not one dead cylinder rough?!!

They pulled the prop through several times and tried it again and again, several times with the same result. Zero compression. You could hear the air blowing out the exhaust system, so we knew it was the exhaust valve. They decided to try "staking" the valve. For those that don't know, that is aircraft mechanic speak for, beat on it with a hammer.

The first several times they tried, nothing, still zero. Not giving up, about the 4th time we got it up to about 25 lbs compression and this gave us hope. One more whack and Voila! Perfect compression on #1. Michael, the IA mechanic there had the theory that just "a piece of crud" got stuck in the guide and it was now free.

I still wanted it checked out, so after I left (I was not able to stay for the whole annual this time) they did the rope trick and checked the fit of the valve in the guide. They said it felt perfect, so no further work was done on it. They ran her up and did another compression check and it came out perfect on all cylinders.

Happy ending, but I still worry about this "piece of crud" and this brings me to my own theory as to where this crud came from. Both my #1 and #2 cylinders run really cold all the time. I have to really flog the engine to get them to go over 300 CHT. They typically cruise about 280 something to 290 something. I run LOP most of the time, but even ROP only raises the CHT about 10 degrees as I keep it at 65-70% power.

I have read that ideally, you need to keep your cylinders over 320 so that the additive that is in 100LL to scavenge the lead can do it's job. I have read that cold cylinders lead to lead deposits. This is exactly what I believe I saw when I had the spark plugs out on #2 last year when I had trouble with my flow divider. It looks like a flaky crust on the top of the piston and presumably, it may be on the top of the cylinder head as well.

Maybe this is where the myth that LOP causes burned valves comes from, because a sticking valve will quickly become a burned valve if it doesn't free itself up. Maybe in some applications like mine, LOP lowers the cylinder head temps so much that lead build up occurs and on occasion, sticking valves from "a piece of crud" breaking loose and getting stuck in the guide.

I have heard of a fuel additive you can get to help scavenge the lead from your cylinders and I'm willing to try it, but what I can't find out from anyone is, does it help remove existing deposits, or does it only prevent future deposits?

Also, Lycoming many years ago released a SI 1418 on how to clean the inside of the combustion chamber with walnut shell medium without removing the cylinder. I asked on the internet about this procedure and few people were familiar with and had to look it up. Most all were very skeptical as to it's usefulness. Anybody here know anything about it? I'm going to ask LASAR about it today.

I'm assuming you have a newer 201 that has the dual mags and used 20 degrees of timing. I think someone on here knew of a way to legally set the timing to 25 degrees on those engines. On mine it's supposed to be set at 25 degrees but the folks at Willmar improperly set it to 20. I had to run hard to get heads over 330. Reset the timing to 25 and walllaaaa. 330-370 depends on how hard it's ran. 25 might be an option.......

[DaV8or]

Alcor TCP is probably what they're referring to.

That's the stuff I was thinking of. Anybody know anything about it? MMO is basically just a solvent, so it may clean up carbon, but I doubt it does anything for lead deposits and if you use it in your oil, you will be diluting the oil and changing it's viscosity. Just something to think about.

[mcpilot]

TCP is Tricresylphosphate.  It s a catalyst that allows the tetraethyl lead in Avgas  to be broken down more easily and removed during combustion.    You might say it disrupts or "softens" the hard lead deposits.

 

I took one of my dental cameras and shot photos of the inside of my cylinders as they were and will retake them after I have flown some hours with the TCP added to fuel.  

 

[DaV8or]

What does the rope trick clean out of the guides?

 

The rope trick is just a means to release the valve from it's keeper and the valve spring without removing the cylinder. The spark plugs are removed and the piston is moved downwards to the bottom of it's compression stroke, then a couple of yards of 1/2" nylon rope is fed into the combustion chamber. Once they feel enough rope is in there, a helper grabs the prop and pushes the piston back up on the compression stroke and holds it there. The piston jams the rope up against the valves and this allows the other mechanic to use a spring compressor to release the keeper and valve spring from the valve.

 

Once it is free to move on it's own, They can feel the binding, or the slop in the guide. If there is binding, the rope is removed and the piston is moved to the all the way down position. At this point the valve is pushed all the way into the combustion chamber and they use a reaming tool to get the valve guide back to the factory sizing. In the case of the IO-360, I think it is exactly .500. Then the valve is carefully guided back into the guide using magnetic and grabbing tools all through the two spark plug holes. This is the hard part and can take a little time. Then the rope is put back in, the piston pressed up to hold the valve in place and the keeper and spring is reinstalled.

 

What comes out from the reamer can be carbon, lead, plain ol' dirt and sometimes bronze because the guide was incorrect to start with.

[DaV8or]

TCP is Tricresylphosphate.  It s a catalyst that allows the tetraethyl lead in Avgas  to be broken down more easily and removed during combustion.    You might say it disrupts or "softens" the hard lead deposits.

 

I took one of my dental cameras and shot photos of the inside of my cylinders as they were and will retake them after I have flown some hours with the TCP added to fuel.  

 

Nice!! How much does that camera cost? Please do share your results. I am really curious to see if this stuff can take away existing lead, or if it just aids in getting rid of the lead contained in the fuel during combustion.

[mcpilot]

You can get them on eBay for around $100. Search for MD740. It's not the cheapest one on there but does a really nice job fr the money. Good quality

It was plug and play on my mac and PC laptops

[mcpilot]

I must say that sticky and stuck valves sound more like the "rule" rather than the exception. Anyone care to put together a poll as to prevalence etc?

[N201MKTurbo]

One thing that is not talked about much is the difference in chemistry when running LOP vs. ROP. When ROP you have a more reducing reaction in the combustion chamber. When LOP you have a more oxidizing reaction in the combustion chamber. The reducing reaction will consume the oxide deposits and leave carbon deposits. The oxidizing reaction will consume the carbon deposits and leave oxides like the lead oxide. You can get pure lead while ROP.

 

I believe to keep your cylinders the cleanest, a little bit of both would be the best solution. I believe the crankcase stays cleaner when running LOP.

 

I just had my engine apart and the inside of the crankcase was very clean except for a light grey coating on everything. I assume it is lead oxide. My cylinders had no carbon anywhere, just some light oxide like deposits around the exhaust valves.

 

 I have run LOP for the last 10 years. The only time I'm ROP is takeoff and climb.

[mcpilot]

One thing that is not talked about much is the difference in chemistry when running LOP vs. ROP. When ROP you have a more reducing reaction in the combustion chamber. When LOP you have a more oxidizing reaction in the combustion chamber. The reducing reaction will consume the oxide deposits and leave carbon deposits. The oxidizing reaction will consume the carbon deposits and leave oxides like the lead oxide. You can get pure lead while ROP.

 

I believe to keep your cylinders the cleanest, a little bit of both would be the best solution. I believe the crankcase stays cleaner when running LOP.

 

I just had my engine apart and the inside of the crankcase was very clean except for a light grey coating on everything. I assume it is lead oxide. My cylinders had no carbon anywhere, just some light oxide like deposits around the exhaust valves.

 

 I have run LOP for the last 10 years. The only time I'm ROP is takeoff and climb.

This is the key...  LOP is complete combustion....  (Stoichiometry)  EAch molecule of fuel when combusted (oxidized) is reacted completely.

[aaronk25]

Run at peak egt best of both worlds. Go faster, run cleaner get where your going this year....enough said.

[jetdriven]

I'm assuming you have a newer 201 that has the dual mags and used 20 degrees of timing. I think someone on here knew of a way to legally set the timing to 25 degrees on those engines. On mine it's supposed to be set at 25 degrees but the folks at Willmar improperly set it to 20. I had to run hard to get heads over 330. Reset the timing to 25 and walllaaaa. 330-370 depends on how hard it's ran. 25 might be an option.......

That was me.  You can run 20 or 25 degrees of timing in your IO-360 engine. Your option. The only difference is a Slick 4372 (20 degree) or 4373 (25 degree) magneto (or Bendix equivalent) in the left side of the engine and a logbook entry about undoing the optional Lycoming Service Instruction 1325A. The Type Certificate for the engine lists 25 degrees as the spec. For those of you that think that is dangerous, the IO-360-A3B6D is only permitted to have the 25 degrees timing. 

 

I have a letter from the US Lycoming sales rep stating it does not void the warranty even on a factory engine, and it is your option to undo the Service Instruction, since it is NOT mandatory. It only took 2 phone calls and 4 emails ( 1 with a service engineer) to get them to say that.   For us on our plane  1977 M20J, -A3B6 it was worth about 5 knots TAS when 15-25 LOP and improves efficiency around 3% on average. The difference in power was certainly noticeable, especially on takeoff and climb. We have verified this on two separate engines, the one ours came with (the -A3B6D), and the one Lycoming shipped us (-A3B6).  We took delivery of both with 20 degrees and set both to 25.

 

Several people have complained about the IO-390-A3A6 not doing any better, and perhaps worse than the IO-360-A3B6D after installation. My theory is that an IO-390 at 20 degrees puts out the same or less power at the prop than the IO-360 at 25 degrees. Its only rated to produce 4-7HP more at altitude than the smaller engine. Overboring a large displacement cylinder that operates at low RPM is a terrible way to increase horsepower, although it did work on the Continental IO-550 but nobody knows why, because its more efficient as well (.38 BSFC.)  Its the same 90 CID per hole as your IO-360. If you increase the stroke and put longer rods in it, the effective rod angle is less allowing more torque on the crankpin, but I digress.

 

It does run warmer at 25 degrees timing but usually less than 380 in cruise, although it flirts with that number at times on #3 and #4 in a 1977 J. 23 degrees timing gives you almost all the gains (you lose 1 knot) while running 10-20 degrees cooler. I'm not advocating that, as its not listed on the TCDS, but Lycoming put a mark on the flywheel at 23 degrees and the experimental IO-360 and IO-390 engines' dataplate is blank where it says "timing".   I have some friends who run 25 in the winter and 23 in the summer to deal with this.

 

We have noticed the IO-360-A3B6 is a different animal than the -A3B6D. The ONLY thing different in this engine is the roller camshaft and lifters.  Cylinders, compression ratio, crank, rods are all the same.  It does not run LOP acceptably without GAMIjectors and it does not respond so dramatically to changing the timing from 20 degrees to 25 as the -A3B6D. Rumors are out there, but my theory is the roller cam engine produced more than the certified limit of 200 HP due to less friction in the valvetrain, so Lycoming changed the camshaft lift and duration, perhaps the lobe center as well, to effectively derate the engine to 200 HP.  That could explain the inability to run LOP on stock injectors as the lobe ramps and lift on the cam cause different intake velocities than the flat-tappet engines.  I dunno, but we ran 193 MPH in two separate air races, beating the old 1200-hour engine by 5 MPH.  After a new round of the full LASAR treatment of speed mods and new paint in a couple months, we are seeking 201 MPH.  To my knowledge, nobody has ever done that before. As well, nobody has ever shoved an IO-360-A3B6 with Bendix 1200 mags in a fully optimized M20J either.

[carusoam]

Byron,

When are you moving to an IO550?

I'm looking forward to your detailed input on the big blocks the way you have covered the IO360s.

Best regards,

-a-

[fantom]

I think when Byron makes that move the IO-550 will be mounted in a Bonanza. But I hope that I am wrong.

Mega ditto....

[wishboneash]

The cylinder was removed yesterday. Here's what the inside looked like.

 

http://mooneyspace.com/gallery/image/34377-cyl1-a-io-360-a3b6/

[garytex]

I don't know how germane this is to our engines but marvel mystery oil got it's big push into the aviation world when the airlines started running it in their DC 3 motors to alleviate valve sticking

[jetdriven]

The cylinder was removed yesterday. Here's what the inside looked like.

 

http://mooneyspace.com/gallery/image/34377-cyl1-a-io-360-a3b6/

That's totally a cylinder shop issue. Who redid the cylinder?

I know IO-360 cylinders are awfully expensive, something like 2300$ each, but I think I would toss that one and put a new one in that hole.

[wishboneash]

That's totally a cylinder shop issue. Who redid the cylinder?

I know IO-360 cylinders are awfully expensive, something like 2300$ each, but I think I would toss that one and put a new one in that hole.

Air West at KSQL. I am going to get another cylinder, not going to try and repair a second time.

[fantom]

That's totally a cylinder shop issue. Who redid the cylinder?

I know IO-360 cylinders are awfully expensive, something like 2300$ each, but I think I would toss that one and put a new one in that hole.

 

I believe used ones in excellent refurbished condition can be found for ~ $1,000.

[jetdriven]

The only thing you can judge on a rebuilt cylinder is the quality of the paint job .   I read somewhere that around 6-8K hours the aluminum threads in the barrel fatigue out and the head blows off the jug. There is no way to know how many hours are on a rebuilt cylinder.  I dont think that's as much of a problem on a 7.5:1 motor but these angle-valve engines are 8.7:1 and the cylinder pressure is up there.  a cowker used to fly the SIX, as in DC-6, and he blew jugs all the time, two in one day. There are no new ones available so they keep rebuilding the 60 year old ones. 

 

I was willing to rebuild my first-run cylinders on my last engine like Scott Selllmeyer did, but we didn't get that option. The cylinders were fine it was the rest of the motor was shot.

 

Ash, can you specify a first-run rebuilt cylinder next time around?   The R&R labor will more than cancel out the 1100$ in savings on a rebuilt unit if it goes bad again.  And its gone bad twice already in 250 hours.

[wishboneash]

 

 

Ash, can you specify a first-run rebuilt cylinder next time around?   The R&R labor will more than cancel out the 1100$ in savings on a rebuilt unit if it goes bad again.  And its gone bad twice already in 250 hours.

 

Thanks for the advice, Byron. That's precisely what I plan to do. Get a Lycoming first-run cylinder. It's likely to be steel rather than cerminil.

[fantom]

How can one be certain it's first run?

[jetdriven]

They are all "first run cylinders".  I assume that answer was developed right about the time pilots got wise and started asking for them.

[fantom]

They are all "first run cylinders".  I assume that answer was developed right about the time pilots got wise and started asking for them.

[jetdriven]

Wow, check out that tatoo!