Cylinder Overhaul – The Basics

Rob58

Rob58

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Is there a standard checklist of what gets accomplished and what gets replaced as part of a cylinder overhaul? …or is this just a general term that means different things to different shops? Trying to learn something!
 
I just had a cylinder repaired at http://www.hhtriad.com/ for an exhaust valve issue. These guys do this stuff all day long so my cylinder came back with new valve guides, leaked tested, honed again, and needed a new break-in period. Here are some before and after pictures.

Before
IMG_6349-scaled.jpeg


After
IMG_6357-scaled.jpeg
 
How’s the cylinder shop to IRAN The cylinder. Last year I replace the cylinder with a bad exhaust valve and guide. The cylinder bore was fine. The shop merely replaced the valve guide and valve. After reinstallation there was no break in period for the cylinder since the old rings, piston, etc. worked fine and were already broken in.

your situation may be different. Do you consider an IRAN instead of a complete overhaul with a re-honing of the cylinder.
 
Rob58 said:
what gets replaced as part of a cylinder overhaul?
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FYI: most cylinders get repaired or rebuilt vs overhauled. Usually when a shop needs to separate the cylinder head from the cylinder/barrel to fix, the cost starts to get closer for either an exchange cylinder or sometimes new cylinder depending on the total engine hours.
 
there really isn't set rules for what "overhauled" means, so the shops can say most anything.

remember SBs are not mandatory.
 
The ones I have spoken to seem to shy away from calling them overhauled anymore. They just ask what needs repaired or what you would like to have done. Things like Chroming, new valves, etc..
 
Grum.Man said:
The ones I have spoken to seem to shy away from calling them overhauled anymore. They just ask what needs repaired or what you would like to have done. Things like Chroming, new valves, etc..
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The 8030-3 paper work places the requirement to state what was done. (FAR 43)
43.2 Records of overhaul and rebuilding.
(a) No person may describe in any required maintenance entry or form an aircraft, airframe, aircraft engine, propeller, appliance, or component part as being overhauled unless—

(1) Using methods, techniques, and practices acceptable to the Administrator, it has been disassembled, cleaned, inspected, repaired as necessary, and reassembled; and

(2) It has been tested in accordance with approved standards and technical data, or in accordance with current standards and technical data acceptable to the Administrator, which have been developed and documented by the holder of the type certificate, supplemental type certificate, or a material, part, process, or appliance approval under part 21 of this chapter.

(b) No person may describe in any required maintenance entry or form an aircraft, airframe, aircraft engine, propeller, appliance, or component part as being rebuilt unless it has been disassembled, cleaned, inspected, repaired as necessary, reassembled, and tested to the same tolerances and limits as a new item, using either new parts or used parts that either conform to new part tolerances and limits or to approved oversized or undersized dimensions.
 
Not everything is equal, a vendor (CRS) can create their own proprietary procedures and have them approved even if the OEM doesn't have specific overhaul instructions/specifications in their ICA. Said CRS then should list those procedures by document number and revision on the 8130-3 or yellow tag accompanying said parts.

The biggest players doing this that i can think of is instrument shops. All your old analog airspeeds, altimeters, VSIs, TC, gyros and more.

If you wold like to know what one cylinder shop does I would call them and ask. You may want more parts replaced then they normally do.
 
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bnt83 said:
Not everything is equal, a vendor (CRS) can create their own proprietary procedures and have them approved even if the OEM doesn't have specific overhaul instructions/specifications in their ICA. Said CRS then should list those procedures by document number and revision on the 8130-3 or yellow tag accompanying said parts.

The biggest players doing this that i can think of, is instrument shops. All your old analog airspeeds, altimeters, VSIs, TC, gyros and more.
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A&Ps can repair on a work order or on the aircraft aircraft / engine log. and may encompass more than 43.2 requirements.
 
bnt83 said:
(CRS) can create their own proprietary procedures
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And quite a few CRSs do when it comes to the repair side which keeps the owners costs down. Especially on the turbine side. But if time is of a consideration, sometimes it's more cost effective to go the exchange route and receive a different cylinder/instrument that has been repaired to those same procedures.
 
Very helpful feedback - thanks! My plan is to talk with a few shops and this helps me ask the right questions. A few more specific questions to my friends here: first of all if I choose to have the cylinder bore honed does that suggest I will need to replace the piston? What amount of clearance is permissible between piston and bore? Can I replace the rings without honing the cylinder? What about flow matching? Seems like there are quite a few variables to consider. I don't want to direct a CRS to perform certain work without being knowledgeable about these details - or at least smarter than I am now. Thanks again!
 
Rob58 said:
Very helpful feedback - thanks! My plan is to talk with a few shops and this helps me ask the right questions. A few more specific questions to my friends here: first of all if I choose to have the cylinder bore honed does that suggest I will need to replace the piston? What amount of clearance is permissible between piston and bore? Can I replace the rings without honing the cylinder? What about flow matching? Seems like there are quite a few variables to consider. I don't want to direct a CRS to perform certain work without being knowledgeable about these details - or at least smarter than I am now. Thanks again!
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Piston only come in .005, 010, and .015 oversized

doing the best way,, NEW cylinders. JMHO
 
Rob58 said:
I don't want to direct a CRS to perform certain work...
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FYI: in most cases, the CRS will provide you with what it will take to repair and sign-off the work. As mentioned above, they have required procedures they must follow and normally can't cherry pick from them. Regardless, once you send the cylinder to them, they will perform a required preliminary inspection which includes looking for hidden/other damage. Afterwards the shop will contact you with what needs to be done to repair the cylinder and a cost estimate. At this point is where I would usually make the call on repairing, exchanging, or going to new cylinders. So to answer your other questions it would be a better tack to discuss those questions with the shop you plan to use prior to sending the cylinder. The last cylinder I sent was damaged during a broken stud removal and the shop found some corrosion pitting that I elected to have repaired also for around $435 as an exchange was around $600 I think.
 
I also think new offers the best value. For me the thing I get repaired always seems to fail for another reason next year. the time and money to take one on and off is the same no matter what you do. There are always special circumstances though so its not always the right decision i guess.
 
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