Removing Cylinders: do I need new rings?

I plan to pull my cylinders to replace the pins with the new style pins with integral steel caps. I will pull them just far enough to get the pins out to avoid the ring compressor.

My question is, will I need new rings and a hone? In order to get the pins out, I will need to drag the rings through the rough surface outside the normal travel zone. I am guessing this is done for inspection all the time and I am hoping that those with experience can tell me if I will likely run into problems with oil burning by doing this. I don't want to go through another break-in, but also don't want to end up pulling the jugs a second time to deal with oil burning.

I appreciate your guidance and experience here.

Larry

lr172 said:

I plan to pull my cylinders to replace the pins with the new style pins with integral steel caps. I will pull them just far enough to get the pins out to avoid the ring compressor.

My question is, will I need new rings and a hone?

Click to expand...

No........

Only If

If you don't pull them out to far and then break one while putting it back in place you should be just fine. Go slow and be careful. you'll be fine.
Hope this helps, yours, R.E.A. III #80888

What Dan said.

Thanks guys.

Larry

As long as the pin slides out nicely it will be fine, but often the piston pin hole is varnished or carboned up and the pin won't come out easy. If so if will be very tricky to keep the rings in place while tapping on the pin with a wooden dowel, you have less than 1/8" between pin clearence and the oil ring peeking out. A little brake clean or acetone may dissolve the varnish. Heat also helps but with the piston in the cylinder it will be hard to heat it enough to help.
ACS sells a pin pusher, I've never used one but it looks like to make it work you'll end up with the rings all the way out. If they do come out the decision to replace and hone can be argued both ways. If not too many hours, handled carefully, kept clean and put back carefully you could probably get away with putting it back together, but it's a bit of a gamble.
Tim Andres

tim2542 said:

...you'll end up with the rings all the way out. If they do come out the decision to replace and hone can be argued both ways. If not too many hours, handled carefully, kept clean and put back carefully you could probably get away with putting it back together, but it's a bit of a gamble.

Click to expand...

Sincere technical question.....why is it a gamble? Let's assume reasonable skills and careful handling, i.e. damage or dirt not a factor.

It's not a gamble. Piston ring and cylinder bore surface finishes do not spoil when exposed to light or air. I would however buy or borrow a band type ring compressor. There is very little chance that you will be able to support the cylinder and remove the wrist pin plugs without the rings sliding out of the cylinder bore. Furthermore trying to support a cylinder with one hand, while trying to change parts is a easy way to damage parts. It will be way easier to slide the cylinder off, change the parts, then slide the cylinder back over the piston using a ring compressor.

http://www.aircraft-tool.com/shop/detail.aspx?PRODUCT_ID=1670

The ACS cylinder removal tool works really well. I can attest to that during the TOH of my RV10. If your piston pins all slide out just by pushing, go by a lottery ticket. Out of 6, only one or 2 pushed out with finger pressure. The rest required the tool, which won't fit with the cylinder in the way. The article is in the latest release of KP magazine if you want pictures.

Vic

I have ring compressor. I suppose I will pull them off completely. I was just trying to avoid more scratching of the rings. Other than the overhaul and the new rings/re-hone on #2 @ 10 hours, I have never pulled one, so didn't think that much about the carbon build up.

Thanks for the tips.

Larry

Mike H said:

It's not a gamble. Piston ring and cylinder bore surface finishes do not spoil when exposed to light or air.

Click to expand...

My concern was running the rings over the coarse area of the cylinder wall. Honing purposely (prior to modern Plateau honing) leaves a rough surface to force the rings and wall to wear into smooth and compliant surfaces. I was afraid that introducing new scratches to the rings might cause a problem as they cannot easily polish themselves after re-installation, as the cylinder wall is too smooth to allow that.

I don't have enough knowledge to know the answer to this and thought I would follow the wisdom of those with more experience in this area. I have heard in the high end engine arena, guys will not put old rings back in. Just didn't know if that was precaution/overkill or a necessity.

Larry

I have removed multiple cylinders and reinstalled them without changing the rings or honing the bores. There was no difference in oil consumption or compression leak down on any of these cylinders. I personally find it hard to believe that the piston speed and distance that a set of smooth faced, broken in rings, will travel over the honed surface in the lower end of the cylinder bore during cylinder removal and installation would cause any appreciable wear.

Mike H said:

I have removed multiple cylinders and reinstalled them without changing the rings or honing the bores. There was no difference in oil consumption or compression leak down on any of these cylinders. I personally find it hard to believe that the piston speed and distance that a set of smooth faced, broken in rings, will travel over the honed surface in the lower end of the cylinder bore during cylinder removal and installation would cause any appreciable wear.

Click to expand...

Thanks for sharing your experience. I appreciate it.

Larry

DanH said:

Sincere technical question.....why is it a gamble? Let's assume reasonable skills and careful handling, i.e. damage or dirt not a factor.

Click to expand...

I think Mike is right, but it's hard to argue against Lyc and the PMA guys who will say replace the rings and hone, they sell parts and I guess want to put everything back like new every time.
Really the only thing I can think of that could get you in trouble would be carbon buildup in the ring lands displaced causing a ring to bind in the land or break when it's compressed.
If you do pull them out of the cylinders, don't let the rod drop onto the case, and it would be a good time to check your exhaust guides and cam lobes/followers.
Tim Andres