Replacing a cylinder

[RMCN172RG]

The bird is in for annual and the bad news, so far, is that #3 is testing 30/80, it was 60/80, last year all others are in the low 70's. Problem is the Intake valve. I've been told that I can either replace the cylineder with a new Lycoming one or send this one out for rework. For the cost differential new seems to me to be the better option. Thoughts?

My question / concern at this point is do you break in a single cylinder the same way you woul dbreak in a new engine?

 

[ScottM]

The bird is in for annual and the bad news, so far, is that #3 is testing 30/80, it was 60/80, last year all others are in the low 70's. Problem is the Intake valve. I've been told that I can either replace the cylineder with a new Lycoming one or send this one out for rework. For the cost differential new seems to me to be the better option. Thoughts?

My question / concern at this point is do you break in a single cylinder the same way you woul dbreak in a new engine?

If go the new cylinder route, please look at my experiences with ECI.

How many hours on the current jug? Can a new valve fix the problem?

 

[charlie]

If you can have the cylinder repaired for $500 why spend more than double that for a new one. Breakin is no problem. Mineral or 20-50 X/C oil, leave the throttle open and reduce RPM to 2,500 for climb. Run 75 % square as much as practical. Charlie Melot Zephyr Aircraft Engines

 

[RMCN172RG]

If go the new cylinder route, please look at my experiences with ECI.

How many hours on the current jug? Can a new valve fix the problem?

A little over 1000 SMOH on the engine. I am well aware of your experience that's why I'm looking for other opinions.

If you can have the cylinder repaired for $500 why spend more than double that for a new one. Breakin is no problem. Mineral or 20-50 X/C oil, leave the throttle open and reduce RPM to 2,500 for climb. Run 75 % square as much as practical. Charlie Melot Zephyr Aircraft Engines

I was quoted 7-800 so the difference there seems to make new the better option.

That's pretty much how I run anyways.

 

[ScottM]

A little over 1000 SMOH on the engine. I am well aware of your experience that's why I'm looking for other opinions.



I was quoted 7-800 so the difference there seems to make new the better option.

That's pretty much how I run anyways.

But is it just the new valve?

If so I would be tempted to just have the valve work done and maybe new rings.

 

[Trapper John]

If go the new cylinder route, please look at my experiences with ECI.

Partially related, did you see the new mandatory service bulletin for Continental cylinders? Something like 9,000 cylinders potentially affected, but Continental is stepping up with free replacement including labor...kind of makes that other replacement cylinder brand look even worse than they already are, if that's even possible...


Trapper John

 

[Trapper John]

But is it just the new valve?

If so I would be tempted to just have the valve work done and maybe new rings.

Yeah, I think I'd just fix the bad valve. I wouldn't mess with the rings if the rest of the cylinder is happy.


Trapper John

 

[ScottM]

Partially related, did you see the new mandatory service bulletin for Continental cylinders? Something like 9,000 cylinders potentially affected, but Continental is stepping up with free replacement including labor...kind of makes that other replacement cylinder brand look even worse than they already are, if that's even possible...


Trapper John

ECi did that the first time I had problems with their cylinders. The 2nd time, which was only 250 hours later all they would consider was warranty replacement. I just got tired of their failure to make a cylinder that could go the distance.

 

[ScottM]

Yeah, I think I'd just fix the bad valve. I wouldn't mess with the rings if the rest of the cylinder is happy.


Trapper John

I was thinking of maybe the rings if the jug has to be pulled and the piston is removed. Adding new rings would take like ten minutes.

 

[Trapper John]

I was thinking of maybe the rings if the jug has to be pulled and the piston is removed. Adding new rings would take like ten minutes.

But you should just be able to pull the head to repair the valve, right? As you can probably tell, I'm from the don't fix anything that isn't already broken school of wrenching...


Trapper John

 

[ScottM]

But you should just be able to pull the head to repair the valve, right? As you can probably tell, I'm from the don't fix anything that isn't already broken school of wrenching...


Trapper John

I don't think that you can just pull the head on most airplane cylinders. The problem with the last batch of ECIs I had was that the head was coming loose from the cylinder, they seemed to be press fitted together, no bolts held them.

Charlie, please chime in, you are the expert.

 

[Trapper John]

I don't think that you can just pull the head on most airplane cylinders. The problem with the last batch of ECIs I had was that the head was coming loose from the cylinder, they seemed to be press fitted together, no bolts held them.

Duh, I wasn't thinking!


Trapper John

 

[RMCN172RG]

I don't think that you can just pull the head on most airplane cylinders. The problem with the last batch of ECIs I had was that the head was coming loose from the cylinder, they seemed to be press fitted together, no bolts held them.

Charlie, please chime in, you are the expert.

You mean it's not like working an a 60's inline six.

 

[Dan Thomas]

I was thinking of maybe the rings if the jug has to be pulled and the piston is removed. Adding new rings would take like ten minutes.

If you stick new rings in, the cylinder has to be honed or the new rings will never seat. The cylinder and rings have to chew on each other for awhile to get a decent seal between them, and a glazed cylinder isn't going to do that.

Intake valve leaking?? Very unusual. They don't usually burn because they run so cool. A quick look at the valve and seat should tell you whether:

-The guide is worn and the valve isn't seating square and has worn the seat oval, or

-There's a chunk of lead or carbon stuck to the seat or valve face, or

-The valve seat or face is corroded and pitted, or

-The valve is burned because the hydraulic lifter's piston is seized and not letting the valve seat properly.

Putting some pressure on the cylinder (with the differential tester) and striking the valve stem (rocker end) with a rubber mallet can often dislodge carbon or other crud. If this compression has been dropping steadily after several runs, though, I doubt that it's anything so simple. Still, a quick valve and seat grind should fix it. It's not totally shot if there's still 30/80.

How old is the engine? Lycoming had poor valve guides up until late '98 or early '99. Exhaust valves, especially, would end up striking the seats off-center and wearing themselves out.

Dan

 

[weirdjim]

1. Intake valve? I don't think I've seen but three or four of them in the last few dozen years go bad before the exhaust valve is toast. Check again and see where it is hissing.

2. Use the old rings? Probably not a good idea. Honing and ringing isn't that big a deal and it is the best way to go.

3. If it IS the intake valve, remove the rocker arm and see if that clears it up. If so you've got rocker, pushrod, or cam follower problems.

4. If not, pressure the cylinder up. Cover the head of the valve stem with a hunk of thick aluminum or medium thick steel and then use a center punch and hammer to give a couple of short but forceful blows to the head of the valve.

5. If this doesn't do it, wiggle the valve stem. If there is more than the slightest bit of play you've got a worn guide.

Consider yourself lucky. Intake valve problems are about the cheapest thing that can happen to a cylinder.