The International Cessna 170 Association

I don't have any access to mo-gas. I run 100LL and usually add a small amount of MMO. I also lean on the ground and in any cruise above 2000ft or so.

Thanks for sharing those photos! They are invaluable to others who have not seen this sort of failure.

When cylinders are overhauled/rebuilt/repaired/chromed/etc., the methods can vary, and the number of cycles, and/or overhaul/rebuilds can be lost to history. Here's how:
A new cylinder is run until it needs repair or until the engine does, and the cycles or operating history of cylinders on Part 91, private aircraft are usually not recorded. The cylinder may actually not need extensive re-work and may be honed and put back into service. It may be bored out .005" and also returned to service with .005" oversized pistons/rings.
Next engine-life-cycle, the cylinder may be bored out .015" and returned to service with appropriately oversized pistons/rings. The cylinder can run all the way thru a third engine TBO and then be sent to a chrome facility.
It may then be bored out still further inorder to bring it to a standardized oversize....then chrome-plated back to original size, and then put into a freshly overhauled/repaired engine. It can then operate still more un-recorded cycles ...and then the process can start over yet again.

Some cylinders in present service, especially those which were routed thru and "exchange" program, are thus of unrecorded/unknown history...their owners may have only a record of its LAST chrome job...without any clue as to it's former useage. There is no way to know how many times it was re-bored, chromed, re-chromed, etc etc. Subsequent owners/purchasers of "overhauled" cylinders from shops may have absolutely no way of knowing it's history prior to the last rebuild.

This cylinder is cracked in a fairly unusual area....apparently in the mid-section of it's steel barrel...NOT at it's juncture with the threaded aluminum head (which is where cyls usually fail after such history.) I suspect this cylinder suffered from machine-mark stresses beneath it's chrome plating, possibly having been machined/re-bored multiple times. It's a good example/reason to purchase new cylinders when overhauling/rebuilding engines unless each cylinder history is KNOWN, (such as if it had been owned since NEW and is rebuilt specifically for it's owner for re-use...not merely "exchanged" for a newly recertified cylinder.

gahorn wrote:...It's a good example/reason to purchase new cylinders when overhauling/rebuilding engines unless each cylinder history is KNOWN, (such as if it had been owned since NEW and is rebuilt specifically for it's owner for re-use...not merely "exchanged" for a newly recertified cylinder.

I've known of cases where an owner sent cylinders to a shop and got back different ones than what he sent in. An error like that might be hard to detect, and then you think you know what you've got....

Cylinder serial numbers should be recorded, not only during removal/replacement, but when submitted for repair/overhaul. Those serial numbers should be noted on invoices and noted by repair records.

Hello everyone,

Just a quick note to say that the repairs were completed earlier this week and I picked up the airplane a couple of days ago. Running smooth and strong (and smoke free ) once again, but still planning to replace the remaining three cylinders some time in the spring. Until then, I'll be breaking in the recent replacement and keeping a watchful eye out for mysterious leaks, noises, or any other such concerns.

Thanks for all of your comments and support over the past few weeks. See you up there...

-Kennet