Am I seeing LOP at about 1:10 and then ROP about 2:10?
Fix the fuel flow indication and things may get a lot easier. Most of us get grouchy at display dithering of 0.2, and you're over 1 GPH in steady state cruise.
Am I seeing LOP at about 1:10 and then ROP about 2:10?
Fix the fuel flow indication and things may get a lot easier. Most of us get grouchy at display dithering of 0.2, and you're over 1 GPH in steady state cruise.
The best we could tell the valve stem measured .4935, and the valve guide measured .4935.
The intake valve on #2 seems to be working fine, the exhaust however wins the award for the most stuck my A&P has tapped with a mallet.
I did do some calling around and couldn't find anyone with a suitable reamer except for sky geek, it was almost $1000. Any ideas where to find a piloted valve guide reamer .4975-.4985?
Mind telling how you determined the intake was fine?
Mind telling how you determined the intake was fine?
Mind telling how you determined the intake was fine?
Note that the intake valve is not rotating either. Look at the wear on the top of the stem.
Note that the intake valve is not rotating either. Look at the wear on the top of the stem.
My trusted A&P/engine guy has his own reamer for this, if yours doesn't I would find more help before pulling the jug.
Absolutely agree that " staking a valve " or just freeing a valve is no fix at all. I will respectfully disagree that a guide that is well within service limits will not carbon up. Lycoming service bulletins also make that clear but it is certainly fine if the OP elects to pull the cylinder. I was simply offering a much less labor intensive fix that is indeed factory authorized. No offense taken or intended towards anyone.
Keith
Also less invasive,,,, the less you take apart the less chances for mistakes. And yes you are correct they can carbon up when there well in limits.
I would like to see one of the engine builders weigh in on what they think about perfectly good valves and guides seizing up due to carbon accumulation. If this was reality everyone that owned a Lycoming would be "reaming" exhaust guides every few hundred hours as preventative maintenance. I work on quite a few piston aircraft each year and never have to "ream" exhaust guides to keep engines running.
As far as the less you take apart the less chances for mistakes goes....when an engine is broken and does not run correctly, I prefer to disassemble the engine to such extent necessary to identify and correct the root cause, not address the symptom and just make it run one more time. Besides if you cannot remove and reinstall a cylinder on an aircraft engine without making mistakes and causing potential problems or damage, then maybe you should get some qualified help.
I would like to see one of the engine builders weigh in on what they think about perfectly good valves and guides seizing up due to carbon accumulation. If this was reality everyone that owned a Lycoming would be "reaming" exhaust guides every few hundred hours as preventative maintenance. I work on quite a few piston aircraft each year and never have to "ream" exhaust guides to keep engines running.
FWIW, the reaming/measuring procedure is recommended after a 1000 hours if I'm not mistaken.
Mike, how long in your experience does it take for a sticking valve to reoccur after reaming? I've had a badly stuck exhaust valve approximately 60 hours ago, and a mechanic from an overhaul shop reamed the guide and measured its ID (which was fine). It has been running fine since. I'm wondering if I should expect this to happen again soon.
I think the bottom picture shows cause. Black gob and mirror looking channel chrome.
Inside #2, the exhaust valve has a little powdery yellow residue that wasn't present in the other cylinders.
Onto the cylinder shop with the top end, hopefully a couple pairs of trained eyes to check out the bottom end.
You previously said "We weren't ever able to get the valve seated enough for any sort of compression test on #2." So what did the seat area and seat ring look like, and was the head bent?
Kinda hoped you would make some simple measurements before it went off.
This is a ball gauge. They're used in concert with a good micrometer. Common as dirt.
Measure the guides in the plane of the rocker arm centerline, then perpendicular to the rocker arm centerline (in the axis of the rocker arm pin), three places for each measurement; near the spring end, halfway through the guide, and near the port end.
With the same micrometer, measure the valve stem diameter in the general area of the three locations. Subtract the stem diameters from the guide diameters, and you know the real clearance at each location, in and out of plane. One or both ends will generally have more clearance than the middle when measured in-plane because of rocker arm forces. Out-of-plane may or may not show much wear. The center may or may not be tight.
If the valve that was forced closed using the rope trick was the intake, that may explain the broken intake rocker arm.