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Sticking Exhaust Valve - Diagnosis and Fix!

bullojm1

Well Known Member
Two Saturdays ago I was on my first instrument rating lesson - something I have been putting off for some time now. The lesson was pretty straight forward - climb up to 6,500' heading 360, following by a series of ascending and descending climbs while under the hood. Next up was a VOR/ILS approach into Capital City airport near Harrisburg, PA. After figuring out how to get the Grand Rapids EFIS to properly display the CDI/HSI from the Garmin 430W, we were in business. Next up was a practice hold followed by a GPS approach into York, PA (KTHV).

As we were approaching the fix for the hold, the airplane developed a very noticeable shake. Clearly something was not right with the engine. Automatically without me even thinking, I pushed the mixture full rich and turned on the fuel pump. My CFII looked out the window to point me towards York airport. I didn't have it in sight, as my mind was going a million miles an hour. I was lucky to have him in the airplane to point me where I needed to be. We were still developing power, and we were within easy gliding distance of the airport just in case the engine had other ideas. A glance at the engine monitor showed what the root cause of the issue was - the EGT for the #2 cylinder was non-existent. The CHT was decreasing quickly. It was clear that the #2 cylinder was not producing power.

We were 2,000' over KTHV when the engine all of the sudden started performing normally again. The EGT immediately came back to normal, and the CHT was increasing. I glanced at my flight instructor and we both thought it would be better to put the airplane down back home at KDMW - a short 10 minutes away. We circled over KTHV gaining altitude and listening to the engine. Things seemed fine. All engine parameters looked to be back in the green. We headed to KDMW.

Roughly half way to KDMW, the engine stumbled very quickly. Not enough for the engine monitor to notice anything, but both of us definitely heard something. We stayed high and circled down to a non-event of a landing.

I was lucky to be in the presence of Captain John and his endless knowledge of everything airplane at KDMW. We decowled the RV and started digging around the #2 cylinder. Both spark plugs looked to be in fine condition (EMAG on the top plug with an auto plug, Slick mag on the bottom with a massive electrode plug). Next up was a compression test - 78/80, with the slight leakage coming through the rings (audible noise through the oil filler tube).

Naturally I would be lucky enough to have an intermittent issue. Now how to figure out how to fix it?!?! An engine needs three basic criteria to work - spark, compression and fuel. If the spark was lost, both the EMAG and Slick mag would of stopped firing in that cylinder. If the EMAG would of quit, the other cylinders would have symptons of elevated EGT's. This wasn't the case. The lack of fuel was a more likely symptom, especially if an injector was clogged. However, I found it to be unlikely that an injector would be clogged so immediate, and then unclogged immediately also. Typically when I have had a clogged injector, I get elevated EGT's, and it typically doesn't cure itself. The last issue is a lack of compression. What could of caused this is a stuck exhaust or intake valve being open. An open valve during the compression stroke of the engine would definitely cause the symptoms I saw.


The first step to investigating a stuck exhaust valve was removing the valve cover.
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Next up was removing the rocker valves. To do this, you need to push out the rocker shaft. The rocker shaft is kept in place by the valve cover - the cover prevents the shaft from moving left or right. With the #2 piston at BDC, the shaft pushes out easily with just your fingers.
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I removed the shaft and the two rocker arms and stored them with where they were originally on the engine.
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This is the top of the cylinder with the rocker arms removed.
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There is a cap over the top of the exhaust valve stem. This pulls off easily with a magnet or a dental pick.
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Next up was compressing the exhaust valve spring and removing the keys which hold the valve stem to the top of the springs. There are a number of Lycoming valve spring compressors on the market for $60-$150, but from the looks of the pictures of them online, it looked like something I could easily fabricate. This would save me some money, but more importantly, buy me time as I could get the job done ASAP, instead of waiting for a tool to ship.

I ended up purchasing two pry-bars (Stanley 55-515 12-3/4-inch Wonderbar Pry Bar - p/n 1-55-515 - $12 @ Ace and a Kobalt 7-in Pry Bar - Item #: 117699 / Model #: 62897 - $6 @ Lowes). It took about an hour using the angle grinder to get the shape just right, but it worked flawlessly! I wrapped the tool in electrical tape in order to prevent any scratches on the engine pieces.

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A poor picture of the took in action. I put a 3/8" socket extension through the holes of the rocker shaft for the valve compressor tool to attach to. Pushing down on the tool compressed the valves enough to get the locking keys out.

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After using a dental pick with the spring compressed, the keys holding the top of the valve springs to the valve stem came out.

DSCN4482.JPG
 
Now, the moment I have been waiting for - is the exhaust valve sticking, or is there something else going on with my engine.

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Within about 0.000001 seconds of touching the exhaust valve stem, it was very clear what my issue was - sticky valve! The valve stem was very very tight in the valve guide. I could not spin the valve. I could not wobble it. I could barely push it into the cylinder. I called up Daryl at Superior and let him know what my issue was. His recommendation was to purchase a 0.4995" reamer and clean out the valve guide.

A 0.4995" reamer is on it's way ($25 shipped via Ebay), and I should hopefully have this fixed by the weekend. More pictures to follow of the process.
 
Fast forward a week, and today was the day to fix my sticky #2 exhaust valve. After doing some research, it seemed to make sense to drop the exhaust to get access to the exhaust port on the #2 cylinder.
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It's not much access, but it's enough to be able to grab the exhaust stem once it is out of the guide.
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I used a 7/16 wooden dowel to use a hammed against to push the valve into the cylinder.
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It's tough to see, but I used a set of mechanical pickup jaws to grab the step of the exhaust valve once it exited the guide.
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This tool is amazing - the jaws have a fantastic amount of strength, and there is a built in LED light at the end of the tool. For $8, it's a bargain.
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I bought this 0.4995 reamer off of EBay for around $25 shipped. The total cost to fix this issue is under $50! I'm thrilled with this!.
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I chucked the reamer into my tap-and-die tool and added a fair amount of Aeroshell #5 wheel bearing grease. The grease not only lubricates the reamer, but it also catches any shavings the reamer removed from the guide.
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Rotating clockwise, the reamer is fully inserted into the guide.
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I only went in as far as I needed to with the reamer.
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Pulling the reamer out revealed some interesting black gook it removed from the guide.
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Next was cleaning any shavings out of the valve guide. I inserted a rag into the exhaust port, and then sprayed carb cleaner down the exhaust valve guide.
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Next up was the fun task of getting the valve back into the guide. I used a telescoping magnet down the valve guide to attach to the valve stem. However, the valve needed to be lifted in the cylinder to line up properly with the guide. This modified Popsicle stick did the job. It took about 5 minutes to get the valve back in the guide.
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The valve now moves effortlessly in the guide. I consider this issue fixed!
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Next up was getting everything back together. I re-inserted the rope into the cylinder to keep the exhaust valve closed while I installed the keys.
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A few moment later, the two keys to the exhaust valve are installed.
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And then the cap.
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This is where I lost a little momentum. I had a hard time getting the rocker arms compressed enough for the rocker shaft to be pushed through the arms. It was almost like the pushrods grew longer by a few mills. After doing some research, it seems this is caused by the tappets/cam followers (aka hydraulic lifters) filling with oil and expanding, making the pushrods seem longer.

There were three possible solutions I read on how to overcome this:

1) Remove the pushrods and shroud tubes, remove the hydraulic lifters and bleed the oil out of them with a toothpick.

2) Apply some force to the pushrods for a few minutes - this will cause oil to be bled from the lifters.

3) Use a valve spring compressor to compress the springs on the valve enough for the rocker shaft to fit into the rocker arms.

For the intake valve, I was able to place an Irwin clamp to apply a slight amount of force to the pushrods. This worked great.
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Success! The shaft is through the intake rocker arm.
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Unfortunately the Irwin clamp trick did not work on the exhaust side. One issue was the baffle material got too tall and the clamp didn't have much to grab onto. I did not have a proper spring compressor, nor did I want to remove the shroud tubes for the exhaust pushrod. The last option was to find a way to compress the hydraulic lifter by applying a force to the pushrod.

After battling with different ideas for over an hour (very long frustrating hour, I might add), I came up with the idea to allow the engine to do the work. Although the rocker shaft was too big to insert, I thought I could insert a 1/2" wood dowel, and then rotate the propeller so the camshaft would push on the exhaust pushrod, applying pressure to the exhaust valve spring, and compressing the hydraulic lifter in the process. This worked amazingly well! Within one minute, the lift was compressed enough to allow the rocker shaft to be inserted into the rocker arm!
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The rocker shaft is in place, and the job is done!
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I did go around to the other 3 cylinders to make sure the exhaust valve was not sticking. Good news was no other exhaust valve seemed to have any major friction with the guide. I buttoned everything up and went for a successful 0.7 hour test fight. It's great to have the RV back in service, and I learned a TON about how the topend of this engine works.
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Great write-up which is really going to help me.

Just one question. You mentioned you RE-inserted the rope, but that was also the first mention of rope. When had it been inserted previously?
 
Great write-up which is really going to help me.

Just one question. You mentioned you RE-inserted the rope, but that was also the first mention of rope. When had it been inserted previously?

Bob,

I originally inserted the rope thinking I needed to to remove the exhaust valve spring. However, the valve was so tight in the guide, I didn't end up needing the rope to push between the top of the piston and the valve. After cleaning out the guide, the valve slid freely in the guide, requiring some force to keep the valve as closed as possible to install the keys.

I am torn on the rope method. I have always used it in small motors to be able to pop the flywheel nut off of outboard engines and lawn mowers. However, I read an article recommending against the rope as it could potentially become knotted in the cylinder, causing you to most likely remove the jug. Alternatively, you can use compressed air in the cylinder to push the valve tight against the top of the cylinder in lieu of using the rope. My air compressor is at home for a new wood floor project, so it was either rope or rope for me.
 
Yes, great write-up. It looks like your exhaust flange has some erosion. Were there indications of an exhaust leak?
What do you think lead to the valve sticking in the first place? I know these engines suffer from that, but why one cylinder and not the other three? Does this cylinder run hotter or colder than the others? Is it first or last to peak when leaning?
 
I never noticed the bit of metal missing from the cylinder around the exhaust valve flange. It looks like there has even been some leakage here. Is this anything to worry about?

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I would not worry about the missing metal, but would make sure the leak is fixed so it does not continue to erode. It looks like you are close to the edge of the gasket seating area. I have read some threads on better gaskets than the OEM design. I don't remember the details, but I'm sure someone will have chime in with them...
 
I just got off of the phone with Darryl at Superior. After he looked at the picture, he recommended I stop using the spiral wound exhaust gasket and instead use a the 75118 copper gasket. It will provide more surface area to seal the exhaust to the cylinder.
 
Nice writeup with great pics. Thanks for it. Quite a number of "tricks" required for a task like this.

Also, are you using 100LL exclusively?
 
Nice job

Mike. Great McGiver job. A new nick name for you or
maybe McGruber! Seriously, glad you got back safely, and thanks for
The informative write up.
 
Mike, I have the same engine. I may have missed it but how many hours on the engine?

One of the best write ups I have seen on VAF.
 
Good to read you found the source of the problem. Wish mine had been that easy, but along the way I got a similar education. Compressed air does speed valve removal when you've got the pieces to do so. Go back to enjoying your magic carpet!
 
Glad it's fixed.
As you now know certain certified Lycoming engines have a SB or AD mandating a "valve wobble test" every so many hours. Might be a good idea to get a hold of those instructions, they give more guidance than "the other 3 felt okay".

re post #1: What is a VOR/ILS approach? -:)

Comment #2: It's a lot cheaper to figure out how to set up your avionics on the ground, than it is in the air.

Bob
 
Nice writeup. I have to ask though what would be the cause of the excess carbon buildup and what is to stop it from happening again in short order?
 
Nice writeup. I have to ask though what would be the cause of the excess carbon buildup and what is to stop it from happening again in short order?

Dan,

To be honest I have no idea why one cylinder decided to built up excessive carbon/lead on the guide than the other ones. I checked the other 3 cylinders, and the exhaust valve was smooth as silk. Manufacturing irregularities? Unlucky? Who knows. Some people have recommended the following suggestions:

1) Add Marvel Mystery Oil (MMO) to my fuel and/or oil.
2) Add TCP Fuel Treatment to the fuel to act as a lead scavenger
3) Switch from Phillips 20W50 aviation oil back to Aeroshell

I'm not going to do any of the above. I am going to keep running as I always have to see if the issue occurs again -- with the only caveat in I will check my exhaust valve wobble on every annual now that I know I can do a cylinder in about 15-30 minutes.

If you suspect you have an issue or want me to give a look at your engine, let me know and I will happily fly over to KFDK and assist you.
 
Mike, I have the same engine. I may have missed it but how many hours on the engine?

One of the best write ups I have seen on VAF.

Jim,

Thanks for the compliment! I felt obliged to give a thorough write-up since details on this common issue/fix seemed to be lacking in the inter-webs. 320 hours total on the new Superior IO-360 engine.
 
Mike,

That was a great step by step write up. I learned much by reading it and even feel almost capable of doing the surgery should the need present itself. I hope it never does.

Thank you!
 
Great writeup

Mike, super writeup, very well done.

I am moving this thread to the "ongoing maintenance" forum so others can find it easier in the future.
 
Glad it's fixed.
As you now know certain certified Lycoming engines have a SB or AD mandating a "valve wobble test" every so many hours. Might be a good idea to get a hold of those instructions, they give more guidance than "the other 3 felt okay".

.....

Bob

It's not "certain" engines, it's ALL Lycoming engines. :)

It is SB333C (aka Wobble Test) and is on-line -

http://www.lycoming.com/Portals/0/t...termine Exhaust Value and Guide Condition.pdf

Helicopter Engines – 300 hour intervals or earlier if valve sticking suspected.
All Other Engines – 400 hour intervals or earlier if valve sticking suspected until exhaust valve guides are replaced with guides made of improved material. (Refer to latest revision of Service Instruction No. 1485.)


The SI 1485 describes the hi-silicon valve guides and extends the inspection to 1000 hrs.

http://www.lycoming.com/Portals/0/t... Valve and Guide Identification Procedure.pdf

How to perform the "Lycoming Rope Trick" is described here, and it even tells you that it needs about 8 feet of 3/8 nylon rope -

http://www.lycoming.com/Portals/0/t... Reduce the Possibility of Valve Sticking.pdf


Even with all of the above and the new guides, my Tiger's O-360 had loose valve guides (too much wobble) at 600 hrs on brand new Lycoming cylinders.
 
For those of us not particularly good at making tools, can we assemble a list and source of required tools for this task?

Bob,

My research revealed the following valve spring compressors:

This is from Aircraft Spruce - p/n 12-21520 for $60
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And another option from ACS, p/n 12-00202 for $77.
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SkyGeek sells this variety for $150, p/n ATS3602
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And then there is the Valve Wizard for $150. This is a really nice took as it gives you both hands free to remove the keys.
DSCN4476.JPG



Other tools include:
1) Telescoping Magnet. Make sure to get one small enough to make it down the valve guide (1/2" diameter). The stronger the magnet, the better!
2) Mechanical Pickup (I highly suggest the lighted General Tools p/n 70396 - $8 at Lowes)
3) Pick set - the cheap one from Harbor Freight worked great for me
4) Patience!
 
Sticking valves

Backing up to the photo in post #3 showing the red silicone protecting the oil drain back tube. The threaded rod that clamps the front and rear baffles together goes above the oil drain back tubes not below.


Don B

RV 9 Rebuild in Prohress
 
Trying to quantify some cause/solutions . . .

Mike, why #2 and not others? Were your CHT's higher for #2? Any other indication of temps being higher? I just wonder how much lower temps should be to reduce the carboning of the stems.

Also - what oil brand/grade are you using?

Nice write-up (as usual for you).
 
Curious weather you have ever done a GAMI type check to see which cylinder reaches max EGT first, 2nd, 3rd, and 4th. I wonder if this cylinder is running the richest?
Great write up, Mike!
 
Excellent write up. Pretty gutsy taking it on.

Great write up and it does show how simple these engines really are, however, even though i am pretty handy with a wrench I wouldnt do this myself.

Good on you for the methodical way of relating to us and the work itself. Thanks
 
Thanks Mike...I accessed your site several times while I was building because you were several months ahead of me and the information you provided was always well documented with helpful pictures.
I also installed a new IO-360 Superior, so once again you've provided some valuable stuff.
 
How is one to know if their

exhaust valve guides [have been] replaced with guides made of improved material.

Would there be a logbook entry or is there an identifying mark on the valve guides?
 
Coincidence?

I don't know if it's a coincidence, but my superior engine has just had exactly the same issue with about 440 hours on the tach. Exhaust valve on No. 2 sticking. We ran a standard reamer through it which just picked up the carbon, then honed it. It measured out within spec and no abnormal wear.
So unsure why it carboned up?
Only thing my engine guy did different was to disassemble the lifter and check the dry tappet clearance as well. All good.

I had about 10 seconds of rough running after starting a descent. When I looked at the dynon data it showed the EGT 2 suddenly drop, the other three rise a little, the manifold pressure went up 2 inch's as pumping efficiency was lost, which I guess meant the other cylinders leaned out a bit.

Peter
 
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Mike you said you switched from aeroshell to phillips. How many hours would you say you ran with the phillips before you had the sticky valve.
Last week I had the same problem haven't had time to fix it yet but I had a friend who convinced me to change to phillips and it was about 30 hours later my issues started.
I put almost 200 hours on my motor in less then 60 days with oil changes as close to 33 hours as I can. After I ream my #2 valve and check the rest I am going to switch back to aeroshell. I never had issues until I switched it might not have been the oil but it makes me wonder.

Mike did you also have any build up on your exhaust valve stem itself and if so how did u clean it.
 
Lifters

I don't know if it's a coincidence, but my superior engine has just had exactly the same issue with about 440 hours on the tach. Exhaust valve on No. 2 sticking. We ran a standard reamer through it which just picked up the carbon, then honed it. It measured out within spec and no abnormal wear.
So unsure why it carboned up?

Only thing my engine guy did different was to disassemble the lifter and check the dry tappet clearance as well. All good.

I had about 10 seconds of rough running after starting a descent. When I looked at the dynon data it showed the EGT 2 suddenly drop, the other three rise a little, the manifold pressure went up 2 inch's as pumping efficiency was lost, which I guess meant the other cylinders leaned out a bit.

Peter

Interestingly the Lycoming SB388C, which is just an inspection, states this -

All Engines: Remove push rods, shroud tubes and hydraulic tappet assemblies. Disassemble tappet and clean as described in the applicable overhaul manual.

It seems to me if the cylinder push rod system is disassembled that far cleaning and checking the lifters should be a "must do".
 
Oil Pressure

If you jack up the oil pressure to the top of the green a lot of those valve problems will go away. The Lycoming valves get very minimal lubrication with low to mid green oil pressure. Warning: there are a number of respected experts who do not agree with this, a lot more who do.
 
Top of the Green....

Lycoming on the newer engines(180?) in production aircraft has raised the top end of the green (oil pressure) to about 110lbs, I think.... Don't know how they do this without three feet of paperwork, but the valve sticking issue may have been one of the issues.. I run 90/95lbs all the time (O360.A4M), got 2460hrs TT , then overhaul. No cyls were ever changed or valves roped in 2460hrs.
John
 
Specs...

If you jack up the oil pressure to the top of the green a lot of those valve problems will go away. The Lycoming valves get very minimal lubrication with low to mid green oil pressure. Warning: there are a number of respected experts who do not agree with this, a lot more who do.

The key might be what Cessna did on the "new" 172s -

On almost all of the older Lycoming engine installations, oil pressure for the cockpit gauge is tapped from the rear of the engine, at the oil pump. This location is the highest oil pressure point in the engine. In stark contrast, the source for the oil pressure reading in the two new aircraft is at the forward end of the copilot side oil gallery, which is the lowest oil pressure point in the engine.

They also raised the gauge red line from 100 psi to 115 psi.

Running high is probably good...:)
 
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It's not "certain" engines, it's ALL Lycoming engines. :)

It is SB388C (aka Wobble Test) and is on-line -

http://www.lycoming.com/Portals/0/t...termine Exhaust Value and Guide Condition.pdf

Helicopter Engines – 300 hour intervals or earlier if valve sticking suspected.
All Other Engines – 400 hour intervals or earlier if valve sticking suspected until exhaust valve guides are replaced with guides made of improved material. (Refer to latest revision of Service Instruction No. 1485.)


The SI 1485 describes the hi-silicon valve guides and extends the inspection to 1000 hrs.

http://www.lycoming.com/Portals/0/t... Valve and Guide Identification Procedure.pdf

How to perform the "Lycoming Rope Trick" is described here, and it even tells you that it needs about 8 feet of 3/8 nylon rope -

http://www.lycoming.com/Portals/0/t... Reduce the Possibility of Valve Sticking.pdf


Even with all of the above and the new guides, my Tiger's O-360 had loose valve guides (too much wobble) at 600 hrs on brand new Lycoming cylinders.

Since I am at roughly 430 hrs, I read these docs and then called Lycoming to confirm my 2010 vintage YIO-360-M1B has the new guides and the 400 hr SB does not apply to me. Knock on wood, I don't have any indications of sticking....yet. Hope I can make it 1000 hrs. :eek:
 
Are the engines the same?

i.e.: Is it just a change in limitations, or is the engine physically different in some way?
 
Are the engines the same?

i.e.: Is it just a change in limitations, or is the engine physically different in some way?

Wiki as a source, but-

R22 Beta
Fitted with a more powerful engine, powered by a Lycoming 0-320-B2C piston engine.

R22 Beta II
Fitted with a more powerful engine, powered by a Lycoming O-360-J2A piston engine.



Interesting comment on PDF page 4 of this section of the POH -

http://www.robinsonheli.com/manuals/r22_poh/r22_poh_2.pdf

Says the limit is actually 115 psi, but the pilots on older helicopters must follow the earlier instrument markings due to "regulations". :)
 
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Just curious, but do many of you see max pressures (established by the ball relief in the side of the crankcase) with hot oil? I typically only see this value with cold oil and something other than idle RPM's. When hot, something lower. When really hot say 225 OT, the pressure is in the low 60's. That is with either Phillips multivis or 100 AD.
 
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