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asu4me

Member
I removed 2 cylinders for a camshaft inspection on my 1900 hr O360. The pistons were removed from the cylinders so the piston ring positions will no longer be the same if I were to install the cylinders with the same rings. Oil consumption was about a quart per 7-8 hours.

Should I expect higher oil consumption or likely plug fouling problems if I were to install the cylinder/piston with the rings not being in the same postion as before?

Fly it and watch it, or hone and replace rings now?

Jerry Kosirog
Mesa,AZ
RV-7A Firewall Forward
 
Do you mean the piston ring gaps wont be in the same position, or you removed the rings from the pistons so they wont be on the same Cyl?

It is well proven that the ring gaps don't stay in the same positions... the rings often rotate on the piston, in operation, so that shouldn't be a concern.

Not to say the original rings wont still work if they stay in the same locations on each piston, and they go back in the same cyl they were originally, but it is standard practice to install new rings and hone the cyl.

It is a huge amount of work to remove and install 2 cyl once you have done the baffling, etc. Honing, plus new rings is not that expensive compared to the work involved (if you are paying for shop rate labor anyway).
If you are willing to gamble, and don't care about having to do it all over again if oil consumption is high, you could give it a try... but personally I wouldnt.
 
Gaps won't be in same position. Rings will stay on same piston and installed in same cylinder as removed from. The gaps locations will be close, but not exactly in the same position.

Jerry Kosirog
Mesa, AZ
 
vote new Honeall 4 and new rings all around

I'd plan on doing all 4 cylinders, Hone and re ring
rhill
 
asu4me said:
Gaps won't be in same position. Rings will stay on same piston and installed in same cylinder as removed from. The gaps locations will be close, but not exactly in the same position.

Jerry Kosirog
Mesa, AZ
Click to expand...

Gaps don't matter. The rings rotate during operation so they never stay in one place anyway.
The big question is if you are willing to do the whole thing over again, if your gamble doesn't work out.
 
The rings are supposed to rotate as the engine runs. That's how they're designed. Reassemble it and don't worry about it.

Maybe you're thinking about 2-stroke engines. Some of them have small anti-rotation dowel pins in the ring grooves to prevent rotation, so that the ring ends don't end up in the side port of the cylinder.

Heinrich
 
Rocketbob.. to answer your question about why I inspected the camshaft.. I bought a higher time engine removed from a Cherokee 180 that has been sitting longer than I thought it would be before mounting on the -7 I am working on.

Jerry Kosirog
Mesa, AZ
 
ok makes sense. In that case I would just put it back together and build on!

It is not a problem taking the cylinder off and putting it back on.
 
Yes, but the pistons were removed from the cylinders. The concern is now I will have big time oil consumption and maybe plug fouling since the cylinder-piston-rings interface has been upset
 
asu4me said:
Yes, but the pistons were removed from the cylinders. The concern is now I will have big time oil consumption and maybe plug fouling since the cylinder-piston-rings interface has been upset
Click to expand...

If you didn't/don't damage the rings during removal and install, I would be very surprised if you have a problem re-using the existing. With that said, many have already given you that advice and you seem against it. So , go with your gut and just ring and hone them.
 
So close you may as well ...

How many hours on it? If it's anywhere near 1000 I'd suggest while it's apart you check the exhaust guides. If they are showing wear, I'd pull the other 2 and get the jugs freshened up with guides, maybe a valve grind and re-ring/hone. A mini overhaul for not a lot of money, you'll be adding a bit more life left to whatever is there now.
Clamp the case back up with washers and nuts on the thru-studs while it's apart, maybe 35 lb/ft or so.
Put some cam moly lube back on the cam and lifters, it sounds like it's going back in storage for a while and that will protect those parts in storage and initial start.
By the way, be sure to inspect the followers, that's where you will first find damage, not the cam. And look at the rods and crank for corrosion as well.
Good luck!
Tim
 
There have been people who advise reassembly with the old rings.
There have been people who advise to hone the cylinder and install new rings.
Do a little research on these advisors. Which of them have a lot of Lycoming experience and/or are A&Ps.
 
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asu4me said:
Yes, but the pistons were removed from the cylinders. The concern is now I will have big time oil consumption and maybe plug fouling since the cylinder-piston-rings interface has been upset
Click to expand...

I've done this many times and there is no problem. The rings rotate. Assuming everything is in order there is no reason why a piston can't be re installed with old rings as long as everything goes back together in the same order as things were taken apart.

If the cylinder walls are polished smooth with little to no crosshatch visible I would pull all four, rehone, and put new rings in. With 1900 hours you will have lots of guide wear and you may find that you will have some more work to do.
 
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There are many Lycoming guru's on this forum, so I'd ask them specifically.
But my .02 worth---since you have already remove the pistons, I would have an engine builder ( with the proper bore guages) mic the cylinder and check it for taper. If it checks out, new rings, properly installed, cylinder honed to THAT cylinders manufacturer's specs for finish, and reinstalled. If the cylinder has some taper, you might think about new, or reman cylinders.
I'm not a Lycoming guy, but back in my racing days, thats how we did it.
Tom
 
At 1900 hrs I think you'd be foolish not to do a top ovh of all cylinders if you are planning on continuing to fly it past "TBO".
 
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What do rod bearings (and mains) typically look like with 1900 hrs?

It sounds like a classic cascade, sneaking up on an overhaul with possible hard failures along the way. My non-aircraft engine gut says either reassemble as is or overhaul, but it needs some tuning for Lycomings. What is the typical decision tree for this situation?
 
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