Home | I keep seeing widely differing price quotes for engine overhauls. How can I tell what the differences are?

I keep seeing widely differing price quotes for engine overhauls. How can I tell what the differences are?

I keep seeing widely differing price quotes for engine overhauls. How can I tell what the differences are?

Technical Editor:
One common difference is how the shop really plans to carry out the overhaul. See below:

Lycoming Overhaul Instructions – Mandatory Parts Replacement

Lycoming Service Bulletin 240R (latest revision, 02/05/2003) spells out the parts that are to be replaced during overhaul, repair, and normal service. Here is the direct link to the SB:

This long link may get fractured, so be sure to copy and paste all of it, to use it.

You may be surprised by some of the content, and may be surprised by what isn’t there. This SB can be used to help evaluate overhaul quotes. For example, despite the list, many field overhaulers will not routinely replace the Vernatherm (thermostatic bypass valve), the oil pump body, the oil pump gears (if they are already the correct ones per the AD), mag drive cushions, counterweight bushings in both crank and crank weights, and V-band couplings. This is one way that they “save” you money. Though less common now, many also did not replace engine hoses and hose assemblies, if they “looked OK”. Of course, if the engine is shipped out, it has to fall to the A&P or R&R shop to handle things like the hoses. There are still too many planes out there flying around with nice-looking clean firesleeve on 30 and 40-year old hoses, on the brink of catastrophic failure. None of our members fall in that category, right?!

Note that two crucial omissions from the list are cylinders and pistons. Unless you receive new pistons and rings, and dimensionally new cylinders (via plating, boring oversize, or outright new), you are highly unlikely to make TBO on an overhauled engine. Lycoming automatically includes entirely new cylinder assemblies on all their factory rebuilds and overhauls. Virtually all reputable major overhaul shops also include dimensionally new cylinders and pistons, or entirely new replacement assemblies, in their overhaul quotes.

While it loses much of its formatting, the key SB-240S text is pasted in below, in case you have difficulty with the link:

DATE: February 5, 2003 Service Bulletin No. 240S
(Supersedes Service Bulletin No. 240R)
Engineering Aspects are FAA Approved

SUBJECT: Mandatory Parts Replacement at Normal Overhaul and During
Repair or Normal Maintenance
MODELS AFFECTED: All Lycoming reciprocating aircraft engines.
TIME OF COMPLIANCE: As specified below.

Any time the following parts are removed from any Lycoming reciprocating engine, it is mandatory that the parts be replaced regardless of their apparent condition.
All circlips, lockplates, retaining rings and laminated shims
All counterweight washers
All lockwashers and locknuts
Stressed bolts and fasteners, such as:
Stationary drive gear bolts (reduction gear)
Camshaft gear attaching bolts
Connecting rod bolts and nuts
Crankshaft flange bolts
Crankshaft gear bolt

During overhaul of any Lycoming reciprocating engine, it is mandatory that the following parts be replaced regardless of their apparent condition.
All engine hoses
All engine hose assemblies
All oil seals
All cylinder base seals
All gaskets
Piston rings
Piston pins (thin wall)*
Piston pin plugs
Propeller governor oil line elbow (aluminum)**
Propeller shaft sleeve rings
Propeller shaft rollers (reduction gear pinion cage)
Propeller shaft thrust bearings (all geared drive engines)
Supercharger bearing oil seal (mechanically supercharged series)
All exhaust valves (replace with current exhaust valves)
All intake and exhaust valve guides
All exhaust valve retaining rings
Rocker arms and fulcrums (O-320-H, O, LO, TO, LTO-360-E Series)
Aluminum push rod assemblies (O-235 and O-290 series)
Hydraulic plunger assemblies (Except for P/N 78290, refer to the latest edition of Service Instruction No. 1011.)
All bearing inserts (main and connecting rod)
Cylinder fin stabilizers
Magneto drive cushions
Thermostatic bypass valves
Damaged ignition cables
Crankshaft sludge tubes
Counterweight bushings in crankshaft and in counterweights (See latest edition of Service Instructions No. 1142 and 1143 for instructions.)
Accessory drive coupling springs (supercharged and VO-540 engines)
AC diaphragm fuel pumps
Oil pump bodies (two-piece)
Oil pump gears (Reference latest editions of Service Bulletin No. 524 and Service Instruction No. 1164)
All V-band couplings and gaskets

Requirements for replacement of parts for accessories such as magnetos, carburetors, fuel injectors, AN fuel pumps, and turbochargers are described in the applicable manufacturer’s manual.

* Heavy-wall piston pins P/N LW-14077 and P/N LW-14078 may be
reused; all others should not be reused. See latest edition of
Service Instruction No. 1340 and No. 1267 for replacement data.
** P/N MS-20822-6D aluminum propeller governor oil line elbow must
be replaced with P/N MS20822-6 steel elbow at overhaul. It is
not necessary to replace a steel elbow. (Reference latest
edition of Service Instruction no. 1435 and Service Bulletin
No. 488.)

Dimensional inspections should be carried out in accordance with measurements and tolerances as listed in “Table of Limits” (SSP-1776) for all parts approved for use.

NOTE: Revision “S” adds counterweight washers.

Thank you for adding to the resources available for your Fellow BAC Members.